ProSoundWeb Community
Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Mike Sokol on February 20, 2015, 01:18:55 PM
-
As promised, here's my hacked 3-light outlet tester with an extra neon bulb between the ground contact and a finger touchpad. It's not very bright, but it indeed works. I used a 100K ballast resistor on an NE2 bulb, but if someone was going to manufacture this they would need to engineer a properly blacked-out window for the hot-ground indicator and select the brightest bulb that would fit. Still, this is a step in the right direction, I think.
-
Very kool.... I love it when a plan comes together...
I'm still waiting for my buddy to check out the stinger cap for noise floor so I haven't ordered parts yet... Looks like I don't need to test out the NCNL (non contact neon lamp)...
Does it help if you make the other lamps dimmer?
JR
-
Very kool.... I love it when a plan comes together...
I'm still waiting for my buddy to check out the stinger cap for noise floor so I haven't ordered parts yet... Looks like I don't need to test out the NCNL (non contact neon lamp)...
Does it help if you make the other lamps dimmer?
JR
There's a lot of yellow light bouncing around inside of the yellow plastic housing, so we put a piece of e-tape on the back of the new bulb to shield it. However, I do have an Amprobe unit with a dark red plastic housing that could offer better contrast. I bought a 10-pack of the NE2 bulbs and my boy has a new Dremel tool to play with, so perhaps we'll hack a few more testers together over the weekend.
-
If you know anyone with a 3D printer, you could have a new enclosure made from black material and with internal walls between neons.
Steve.
-
If you know anyone with a 3D printer, you could have a new enclosure made from black material and with internal walls between neons.
Steve.
That's a great idea. The tech school where I sometimes teach has a 3D printer. I could make this a class project for their design students.
-
The Radio Shack catalog from 1983 shows a nearly identical tester to the one you started with listed for a price of $5.95. I am not sure when they first appeared, but after at least 31 years an improvement seems to be well overdue! Interesting that the price point hasn't changed much-I wonder how much the mark up has changed?
-
The Radio Shack catalog form 1983 shows a nearly identical tester to the one you started with listed for a price of $5.95. I am not sure when they first appeared, but after at least 31 years an improvement seems to be well overdue! Interesting that the price point hasn't changed much-I wonder how much the mark up has changed?
From what I remember they've always been $5 or so. Of course in the early 70's gasoline was 29 cents a gallon and the minimum wage was $1.50 per hour. So that tester took at least 3 hours of work to pay for in 1972, but around 1/2 hour of labor in 2015 dollars. I'm sure the new ones are made in China, which is why they can be sold for so cheap.
I still don't know why this 4th hot-ground indicator light has never been in the US versions. Perhaps it's because the designers weren't thinking about Reverse Polarity Bootleg Ground (RPBG) wiring as a cause of hot-grounds. It seems that some countries such as the UK and Canada are VERY concerned with grounding and safety, while others such as Korea and India are way LESS worried about grounding and shock safety.
I'm going to ask my contacts at Amprobe and Klein about this next week. Perhaps they can provide some intel on just why this hasn't been offered here. I think the 4-light outlet tester with hot-ground indicator would be perfect for home inspectors who often come across Knob-and-Tube upgrades which have a greater potential for RPBG mis-wiring.
-
I'm going to ask my contacts at Amprobe and Klein about this next week. Perhaps they can provide some intel on just why this hasn't been offered here. I think the 4-light outlet tester with hot-ground indicator would be perfect for home inspectors who often come across Knob-and-Tube upgrades which have a greater potential for RPBG mis-wiring.
From my experience, home inspectors vary wildly in accuracy-likely because their job requires them to be a jack of all trades, they never really master any. More to the point, the Sure Test and others will indicate a bootleg ground. Usually, when they find anything not right about a ground, they flag it as safety and recommend a "licensed electrician evaluate the system". Bootleg or RPBG are both safety issues-they see no need to delineate which is worse, and their lawyers are probably poorer for them not making that call.
-
More to the point, the Sure Test and others will indicate a bootleg ground.
One thing to be aware of is that the SureTest and Amprobe analyzers won't indicate a bootleg ground on a branch circuit located more than 15 feet from the G-N jumped outlet. That's because 15 ft of wire has sufficient resistance to get over the "bootleg" G-N threshold.
The thing that I've found when troubleshooting hums with a qualified master electrician at my side is that very few of them really understand how ground bonding and series resistance works. I'm not saying that they don't know their job, because they are mostly qualified for wiring installation and probably know code inside and out. But troubleshooting botched up systems requires another level of understanding how electricity really works. I'm not sure that most home inspectors have any real knowledge of electricity, while many (hopefully) will understand obvious code requirements.
-
The thing that I've found when troubleshooting hums with a qualified master electrician at my side is that very few of them really understand how ground bonding and series resistance works. I'm not saying that they don't know their job, because they are mostly qualified for wiring installation and probably know code inside and out. But troubleshooting botched up systems requires another level of understanding how electricity really works.
That is a key concept at lot of "people in charge" do not understand. I have had cont ed instructors teach things that made no sense if you understand electricity-but you are right their key focus is code and code is primarily concerned with safety. Safety is enforced (rightly so), so it often becomes the standard vs will it be efficient/not cause interference, etc. I started out with an electronics interest and "added" the electricians license because it was/is a more viable career in a rural area-but it is hard to sell the "added value" of understanding electricity (of course, I understand more than they do how much I still need to learn-which is why I am here!)
-
I started out with an electronics interest and "added" the electricians license because it was/is a more viable career in a rural area-but it is hard to sell the "added value" of understanding electricity (of course, I understand more than they do, how much I still need to learn-which is why I am here!)
I originally went to school for Mechanical Engineering, added Electrical Engineering, then got my Master Electrician license back in 1978. When I built nuclear missile guidance systems back in the 80's I learned all about calibration and designing test procedures. So I'm super curious about how this stuff actually works and love test gear. I guess that's why I like this forum, it really gets my neurons pumping... ;D
-
One thing to be aware of is that the SureTest and Amprobe analyzers won't indicate a bootleg ground on a branch circuit located more than 15 feet from the G-N jumped outlet. That's because 15 ft of wire has sufficient resistance to get over the "bootleg" G-N threshold.
Understood.... If I were to design a bootleg and/or reversed neutral-ground tester (and I am not) I would design a two part tester. First a transmitter plugs into a distant outlet. The transmitter switches or toggles a load on/off between line and neutral, while switching another load between line and ground. These loads could be switched at different identifiable rates to differentiate which is which.
This test ASSumes that this first outlet is wired correctly. The second part a receiver, plugs into outlets between it and the panel to identify if the ground has the ground signal, neutral has the neutral signal, and both have different signals. If none of the downstream outlets have different signals perhaps the first outlet is bootleg. Of course once you identify that things are not correct you need to start taking wiring apart to identify what is what.
Opening up ground at the panel should quickly identify a neutral/ground swap when that outlet stops working.
The thing that I've found when troubleshooting hums with a qualified master electrician at my side is that very few of them really understand how ground bonding and series resistance works. I'm not saying that they don't know their job, because they are mostly qualified for wiring installation and probably know code inside and out. But troubleshooting botched up systems requires another level of understanding how electricity really works. I'm not sure that most home inspectors have any real knowledge of electricity, while many (hopefully) will understand obvious code requirements.
Rules and wiring standards are used to deliver safety without requiring understanding about how the electrons and holes behave.
I still think an audio output for the receiver end of my two part outlet tester might be more sensitive than a go/no-go tester. Perhaps in addition to.
JR
-
I still think an audio output for the receiver end of my two part outlet tester might be more sensitive than a go/no-go tester. Perhaps in addition to.
JR, as I'm sure you're aware, you've set a pretty high bar with wanting a sender receiver that might be simple enough to act as a go/no-go tester. Of course this would be pretty straightforward with a properly wired system that might have a single failure. But USA wiring is full of combination fails, where something goes wrong and is then patched up incorrectly multiple times, sometimes over decades. Perhaps your instrumentation needs an external SOP test document with a flow chart. That is, a specific series of tests with branches you take depending upon results of each test. So if you start at the top and follow the flow chart, then you'll likely come up with an answer. I then like to do a completely different test and compare results to be sure I'm not fooling yourself. I do think your bootleg tester could be a very important part of this test. I'm just not sure we can replace logical training of the person doing the test. For instance, there's an awful lot of "gut" when I'm doing audio troubleshooting. That is, I keep playing with the circuit in question until something seems to jump out at me. Of course, hindsight is 20-20 but if you see enough failure mechanisms enough times, then that should be the first thing you test for. I think that's the sort of intel that should be included in any Test SOP (Standard Operating Procedure).
-
You can design a lot of decision making capability (thousands of lines of code) into a cheap micro, but to do this you must anticipate all those decisions and quantify limits or bounds for good/bad. This is why I like the concept of an audio sniffer so you can literally listen to the quality of the grounds.
Back a hundred years ago when I was designing audio, I would not only measure how much distortion a circuit made, but listen to that distortion product output to determine how nasty or benign it sounded.
No tool can replace experience, but a good tool can open a window into troubleshooting problems. Back in the day old school electricians could get 99% of it done with a simple neon lamp probe, maybe a lamp load. Modern tools should provide more info and as you have recognized some simple tool are too simple to be safe.
JR
-
No tool can replace experience, but a good tool can open a window into troubleshooting problems. Back in the day old school electricians could get 99% of it done with a simple neon lamp probe, maybe a lamp load. Modern tools should provide more info and as you have recognized some simple tool are too simple to be safe.
I've seen a few demonstrations of AED's (Automatic External Defibrillators) in action, and I've got to admit that they come pretty close to being fool proof since they "talk" you through the procedure. They're so good that emergency rescue teams generally hook them up first thing to feed the patient's vital signs to the hospital. Now, those are expensive devices and have lots of development time since lives are at stake and government mandates in place. But maybe something like that could talk an electrician or inspector through an outlet test procedure. Heck, you can get a Valentine's card that will play back an on-board audio file through a speaker for $5, and a GPS with a voice synthesizer for $100. I know those are high volume products, but maybe there's a little filter down technology that could be incorporated into your tester. For instance, I have trouble getting clients to tell me if they're hearing hum or buzz or power supply hash. Those are all caused by different things, yet are often lumped together in the diagnosis.
-
If there is an audio output to listen to the ground, and a micro, it is relatively simple to add speech output. There is probably enough onboard memory inside a modern micro to hold a bunch of words.
Not sure I would embrace this completely..... "Is the unit plugged in (dumb ass)?" .
JR
-
"Is the unit plugged in (dumb ass)?"
+1
-
If there is an audio output to listen to the ground, and a micro, it is relatively simple to add speech output. There is probably enough onboard memory inside a modern micro to hold a bunch of words.
Not sure I would embrace this completely..... "Is the unit plugged in (dumb ass)?" .
JR
"I'm sorry Dave, I'm afraid I can't test for that. You're making dumb ass mistakes." HAL 8999 (pre Miss Manners personality infusion)
-
I am scanning through an ARRL Handbook to refresh my memory. I came across the following statement:, "A commercially available plug-in tester is the best way to test regular three-wire receptacles." There is no warning about RPBG or caution that this is not a comprehensive bullet proof test. Given the target audience-aspiring HAM's-and the fact that the Handbook is several hundred pages of fairly technical reading that would seem to be a prime location for a little more in depth explanation, I find this a little surprising. Perhaps it is indicative of a widespread lack of appreciation for the shortcomings of the 3 light teater which has prevented a demand for a new improved version.
IIRC, a neon lamp creates a roughly 90 volt constant voltage drop across it, much like an LED creates a 1.2 v drop. This should allow you to size a ballast resistor to limit current through a body to a safe value based on 30-40 volts rather than 120-130 volts. A smaller resistor should allow a little more current which should allow a little brighter light.
-
I am scanning through an ARRL Handbook to refresh my memory. I came across the following statement:, "A commercially available plug-in tester is the best way to test regular three-wire receptacles." There is no warning about RPBG or caution that this is not a comprehensive bullet proof test. Given the target audience-aspiring HAM's-and the fact that the Handbook is several hundred pages of fairly technical reading that would seem to be a prime location for a little more in depth explanation, I find this a little surprising. Perhaps it is indicative of a widespread lack of appreciation for the shortcomings of the 3 light tester which has prevented a demand for a new improved version.
This issue is that, believe it or not I'm the guy who defined what an RPBG is and named it - Reverse Polarity Bootleg Ground. And that was just a few years ago while I was laying out the schematic for a 3-light tester using 100-watt bulbs to load the wiring a bit. After coming up with the explanation and demonstration that a 3-light outlet tester wouldn't discover an RPBG, I showed it to my contacts at Fluke, Amprobe, Triplett and Progressive Industries, plus a bunch more. None of them believed that a cube tester wouldn't find an RPBG or why it was dangerous until they built the demonstration for themselves and tried it. I did send this info to the ARRL forum perhaps two years ago, and they seemed surprised that this condition wouldn't be found with a 3-light tester. The idea that these $5 testers will find all miswiring conditions seems to be part of our DNA. While the manufacturers of these testers will include a little legal note stating that they won't find all miswiring, I don't think they're aware of just how dangerous not finding an RPBG can be. It's about as deadly as you can get.
IIRC, a neon lamp creates a roughly 90 volt constant voltage drop across it, much like an LED creates a 1.2 v drop. This should allow you to size a ballast resistor to limit current through a body to a safe value based on 30-40 volts rather than 120-130 volts. A smaller resistor should allow a little more current which should allow a little brighter light.
Yes, you're correct, and some of these neon bulbs will come on as low as 60 volts, I think. I started with a 100K resistor for this first test, and will probably drop it to 33K or less and test for brightness and fault current. Remember, we need to limit fault/shock current to less than a few mA even if the electrician is standing in a puddle or water, so we have to assume worse case conditions. But with a little tweaking this would be a pretty great upgrade to the 3-light testers. Again, they already have versions of this 4-light tester in the UK for 230 volts, so it seems crazy that they wouldn't have them in the USA. I'm going to contact my guys at Amprobe and Fluke this week and try to get the inside scoop and just why that is.
-
I am scanning through an ARRL Handbook to refresh my memory. I came across the following statement:, "A commercially available plug-in tester is the best way to test regular three-wire receptacles." There is no warning about RPBG or caution that this is not a comprehensive bullet proof test. Given the target audience-aspiring HAM's-and the fact that the Handbook is several hundred pages of fairly technical reading that would seem to be a prime location for a little more in depth explanation, I find this a little surprising. Perhaps it is indicative of a widespread lack of appreciation for the shortcomings of the 3 light teater which has prevented a demand for a new improved version.
IIRC, a neon lamp creates a roughly 90 volt constant voltage drop across it, much like an LED creates a 1.2 v drop. This should allow you to size a ballast resistor to limit current through a body to a safe value based on 30-40 volts rather than 120-130 volts. A smaller resistor should allow a little more current which should allow a little brighter light.
I would size the current limit resistor to prevent injury even if the neon lamp was a dead short (I do not know how neon lamps fail) .. that said you could come down even lower than 20k and still be less than 7 mA with a shorted bulb which in my judgement is sub-lethal. While it could make somebody jump.
I would expect Hams to be pretty alert about grounds. Radio antennas are often earth grounded and if a power ground was dicey they would figure it out pretty quick.
JR
-
This issue is that, believe it or not I'm the guy who defined what an RPBG is and named it - Reverse Polarity Bootleg Ground. And that was just a few years ago while I was laying out the schematic for a 3-light tester using 100-watt bulbs to load the wiring a bit. After coming up with the explanation and demonstration that a 3-light outlet tester wouldn't discover an RPBG, I showed it to my contacts at Fluke, Amprobe, Triplett and Progressive Industries, plus a bunch more. None of them believed that a cube tester wouldn't find an RPBG or why it was dangerous until they built the demonstration for themselves and tried it. I did send this info to the ARRL forum perhaps two years ago, and they seemed surprised that this condition wouldn't be found with a 3-light tester. The idea that these $5 testers will find all miswiring conditions seems to be part of our DNA. While the manufacturers of these testers will include a little legal note stating that they won't find all miswiring, I don't think they're aware of just how dangerous not finding an RPBG can be. It's about as deadly as you can get.
Yes, you're correct, and some of these neon bulbs will come on as low as 60 volts, I think. I started with a 100K resistor for this first test, and will probably drop it to 33K or less and test for brightness and fault current. Remember, we need to limit fault/shock current to less than a few mA even if the electrician is standing in a puddle or water, so we have to assume worse case conditions. But with a little tweaking this would be a pretty great upgrade to the 3-light testers. Again, they already have versions of this 4-light tester in the UK for 230 volts, so it seems crazy that they wouldn't have them in the USA. I'm going to contact my guys at Amprobe and Fluke this week and try to get the inside scoop and just why that is.
I appreciate your effort to spread awareness of this. Perhaps you should trademark RPBG(tm)...
I can't speculate on what people knew or when, but as I have posted before I recall Peavey being sued back while I was still working there, so 15 years ago, because a musician was killed while using Peavey gear when he got between a mis-wired outlet and a correctly wired outlet.
I can't say that I have ever experienced one in the wild, far more open grounds than even bootleg, let alone reverse bootleg.
There should be a special room in hell for anybody doing those.
JR
-
Remember, we need to limit fault/shock current to less than a few mA even if the electrician is standing in a puddle or water, so we have to assume worse case conditions.
Sorry, but even if you design/test this, it is very unlikely this electrician will touch any kind of a contact pad while standing in water-just really makes me uncomfortable.
Seriously,this does illustrate one of the most difficult aspects of automation and testing as JR alluded to-anticipating all possible failure/defective possibilities. Testing for a RPBG seems ludicrous-who would actually do that?-it takes at least one intentional and one unintentional miswire to get there.
I agree about HAMs being savy about grounds-as long as the newbie lives long enough to learn. Sometimes a less than reliable test is worse than no test at all. It would be better to go to the effort to verify with a meter than to use a simple quick test that is not "bullet proof" before putting oneself bewteen two supposed grounds. Same as musicians on stage.
-
Testing for a RPBG seems ludicrous-who would actually do that?-it takes at least one intentional and one unintentional miswire to get there.
Yes but it does happen... if not RPBG perhaps a hot guitar ground from a rogue guitar amp is what killed that musician in Argentina a couple months ago when he grabbed a mic.
JR
-
Sorry, but even if you design/test this, it is very unlikely this electrician will touch any kind of a contact pad while standing in water-just really makes me uncomfortable.
What I really want is a Non Contact Voltage Tester grafted into a 3-light outlet tester. That would do basic 3-light hot-neutral tests at the same time it was checking for a hot ground condition. And because it's capacitively coupled, there's no chance of anyone getting shocked even if you're standing in water.
Hey, I just added a 0.047 stinger cap in series with my 100K ballast resistor for the NE2 bulb, and it still lights up with hot ground just fine. Would that make you feel safer?
Note that I spare no expense in mocking this up. A rubber band is a perfectly acceptable attachment device. ;D
-
Yes but it does happen... if not RPBG perhaps a hot guitar ground from a rogue guitar amp is what killed that musician in Argentina a couple months ago when he grabbed a mic.
JR
All my experiments show that a standard sensitivity (90 to 1,000 volt) Non Contact Voltage Tester will reliably find a guitar or mic with a hot-chassis condition of 40 volts AC or more. I still think that's the best quick test you should do on any stage before allowing the musicians to pick up their instruments. This hot chassis test literally takes only a minute to perform, and has the potential to save lives.
-
What I really want is a Non Contact Voltage Tester grafted into a 3-light outlet tester. That would do basic 3-light hot-neutral tests at the same time it was checking for a hot ground condition. And because it's capacitively coupled, there's no chance of anyone getting shocked even if you're standing in water.
Hey, I just added a 0.047 stinger cap in series with my 100K ballast resistor for the NE2 bulb, and it still lights up with hot ground just fine. Would that make you feel safer?
Note that I spare no expense in mocking this up. A rubber band is a perfectly acceptable attachment device. ;D
You could use the 0.047uF instead of the 100k... I increased to 0.15uF for my GFCI stinger cap so the current would be enough to reliably trip the GFCI's 5+/-1mA , while still below the current that humans get stuck to. Of course you could feel it.. The .047uF worst case is only a couple mA.
JR
-
You could use the 0.047uF instead of the 100k... I increased to 0.15uF for my GFCI stinger cap so the current would be enough to reliably trip the GFCI's 5+/-1mA , while still below the current that humans get stuck to. Of course you could feel it.. The .047uF worst case is only a couple mA.
Steve S.
Would this .047 stinger cap in the line make you feel safe? It would limit the fault current to a few mA even if the neon bulb shorted out. Of course, I don't recommend that anyone stand in water while testing an outlet, but we have to prepare for stupidity as best we can.
-
I would be ok with the cap and neon light in series-there is reasonable redundancy there as far as current limiting IMO.
I spent too much time fixing things that should not have malfunctioned the way they did to really feel "safe" when standing in water, but you have to draw a line somewhere. And, reality is, someone will be asked to test receptacles during the spring when you really can't work on a dry surface outdoors for weeks.
-
One ergonomic consideration with regards to safety of a production tester would be to design and locate the touch pad in a location (maybe on the end?) that would make it unlikely/impossible for a shock to cause you to not be able to release the tester. That way in the highly unlikely event of a double failure, your natural reaction should protect you.
-
One ergonomic consideration with regards to safety of a production tester would be to design and locate the touch pad in a location (maybe on the end?) that would make it unlikely/impossible for a shock to cause you to not be able to release the tester. That way in the highly unlikely event of a double failure, your natural reaction should protect you.
The let-go current threshold is around 10-15 mA... Using a "Y" cap that is certified to not fail as a short circuit of appropriate value (0.047uF) should limit the "worst case" current to around 2 mA @ 120V (4mA at 240V). In practice it will be less.
I am not happy with my 7 mA stinger cap to insure the 6mA GFCI will trip, but I don't expect it to cause injury. I know I can feel <1mA but feeling the shock is generally not a problem unless you are up on a ladder or in a dangerous environment.
Note: Since the "good" result of this tester is a dark lamp, there probably needs to be a lamp test mode (switch?) to test the tester, so an open/broken lamp does not give false good results.
JR
-
One ergonomic consideration with regards to safety of a production tester would be to design and locate the touch pad in a location (maybe on the end?) that would make it unlikely/impossible for a shock to cause you to not be able to release the tester. That way in the highly unlikely event of a double failure, your natural reaction should protect you.
Steve, that's a good point. A touchpad on the side could create a "grab on" effect, while one on the end would likely make your hand bounce off due to reflex. I probably need to build one of these in a little project box rather than just hacking up a factory built unit. There's just not much room inside for all these bits.
-
Note: Since the "good" result of this tester is a dark lamp, there probably needs to be a lamp test mode (switch?) to test the tester, so an open/broken lamp does not give false good results.
JR
Think I'll just build this into a little plastic project case so there's room for 4 Neon bulbs plus a test switch. There's no room in a production tester to fit everything, and this is just a proof of concept anyways.
So do I call the 4th light a "Hot Ground" indicator or what? Of course, it will light up with a finger on the touch pad anytime the ground is hot, even if it's from an open EGC and a leaky appliance.
-
Think I'll just build this into a little plastic project case so there's room for 4 Neon bulbs plus a test switch. There's no room in a production tester to fit everything, and this is just a proof of concept anyways.
So do I call the 4th light a "Hot Ground" indicator or what? Of course, it will light up with a finger on the touch pad anytime the ground is hot, even if it's from an open EGC and a leaky appliance.
Even I could understand "Hot Ground" lit under a red lens.
frank
-
Think I'll just build this into a little plastic project case so there's room for 4 Neon bulbs plus a test switch. There's no room in a production tester to fit everything, and this is just a proof of concept anyways.
Found a cheap plastic project box, courtesy of Radio Shack going out of business. I'm going to use a short Edison plug so it can be rotated in case the outlet is mounted either way, plus a Hot-Ground test button, which will need to be a SPDT momentary contact switch (I think). Plenty of room inside to separate the lights enough to stop the photons from bleeding over.
-
Even I could understand "Hot Ground" lit under a red lens.
frank
Yup, I think that should get the message across. Nice thing is that this will be completely passive with no batteries to wear out.
-
A current limited neon bulb with SP3T switch that selects between; Line, Neutral, or Ground, could both confirm that the neon lamp is good (if it lights for Line position), and that neutral and ground are cold when it doesn't light for them. If the 3pos switch is too expensive (or ugly) multiple lamps could be hard wired with separate touch pads. AFAIK a single touch pad could not be shared to test the multiple connections at the same time (without using extra parts and complexity).
While just reverse polarity (swapped line-neutral) is not immediately dangerous, it is probably good to identify.
Additional neon lamps (or LEDs) could confirm mains power present, and whether the ground connection is floating or not. Using all neon would reduce the brightness differences and not be that much more expensive, while slightly more expensive than the legacy 3 lamp testers.
JR
[edit] After soaking this idea in beer my unconscious engineering team asks why not? What if three neon lamps had one end tied to line, neutral, and ground respectively, while the other leads are all tied together.
While floating the neon lamps would form a voltage divider and perhaps all glow weakly. However if you touch the common lead (through the stinger cap) we should see the Line lamp light up brighter, and the Neutral and Ground lamps go dark. This is about as simple as I can imagine to probe all three.
If I had ordered my own lamps I'd tell you how this works.
There might be some benefit from adding steering diodes in series with neutral and ground bulbs to make them more visible in float mode.
[/edit]
-
A current limited neon bulb with SP3T switch that selects between; Line, Neutral, or Ground, could both confirm that the neon lamp is good (if it lights for Line position), and that neutral and ground are cold when it doesn't light for them.
The real trick is to come up with a KISS sequence that's easy for housing inspectors and journeyman electricians to understand. I think that too many switches complicate the logic process, even though guys like you and me with extensive engineering backgrounds tend to love them. I've got to think this through, but your suggestion of blocking diodes just might work, but the Neon bulbs will only glow on one electrode, not both. But I do like the idea of additional verification of hot and neutral polarity. More to think about.
-
The real trick is to come up with a KISS sequence that's easy for housing inspectors and journeyman electricians to understand. I think that too many switches complicate the logic process, even though guys like you and me with extensive engineering backgrounds tend to love them. I've got to think this through, but your suggestion of blocking diodes just might work, but the Neon bulbs will only glow on one electrode, not both. But I do like the idea of additional verification of hot and neutral polarity. More to think about.
OK forget the switch and steering diodes. What happens from the simple 3 neon lamps tied to Line/Neutral/Ground with a common touch node (with stinger cap in series)? That is as KISS as I can think of.
JR
PS: I'd know the answer already but I didn't order my parts yet.
-
OK forget the switch and steering diodes. What happens from the simple 3 neon lamps tied to Line/Neutral/Ground with a common touch node (with stinger cap in series)? That is as KISS as I can think of.
JR
PS: I'd know the answer already but I didn't order my parts yet.
I've already played with this, and if the wiring is correct the Hot bulb will be on, the Neutral bulb will be off, and the Ground bulb will be off. Any other light sequence indicates mis-wiring. And this tester won't be fooled by an RPBG with a hot ground and neutral. However, because of the low current draw, it could be fooled by so called "ghost voltages". So it's not the final troubleshooting tool, but it will indicate that you need to do more testing.
-
I've already played with this, and if the wiring is correct the Hot bulb will be on, the Neutral bulb will be off, and the Ground bulb will be off. Any other light sequence indicates mis-wiring. And this tester won't be fooled by an RPBG with a hot ground and neutral. However, because of the low current draw, it could be fooled by so called "ghost voltages". So it's not the final troubleshooting tool, but it will indicate that you need to do more testing.
You have seen it light from Ghost currents? IIRC I measured something like 250uA of leakage current in my kitchen outlet grounds measured to a cold water pipe. It wouldn't leak that much current to a human current sink. I didn't feel the electricity unless I was touching both grounds.
Placing a resistor in parallel with the ground neon bulb could scrub off some modest amount of leakage current and drop the voltage across the lamp, but this adds to the potential current the human tester is exposed to so I would probably start these resistors at or above 100k(?) range.
If GFCI breakers tolerate 5mA of ground leakage it may be difficult to ignore than much leakage. A tester that is too sensitive is better than one that misses hazards IMO. :o
Thank you for the follow-up.
JR
PS Sorry to keep bugging you with this, I am still waiting for feedback from my other long distance information source about sizing my stinger cap for noise contribution.
-
I've already played with this, and if the wiring is correct the Hot bulb will be on, the Neutral bulb will be off, and the Ground bulb will be off. Any other light sequence indicates mis-wiring. And this tester won't be fooled by an RPBG with a hot ground and neutral. However, because of the low current draw, it could be fooled by so called "ghost voltages". So it's not the final troubleshooting tool, but it will indicate that you need to do more testing.
Actually, I think you need two more neon lamps. Hot-neutral and hot-ground. A disconnected ground or neutral will not trigger a fault condition if you just use a neon on each wire.
My suspicion is that it won't be as susceptible as some NCVT are since it does draw some current. Perhaps the hot-neutral and hot-ground lights could be ballasted to draw the max current the neon can handle. Then a high percentage of the ghost voltage would likely cause the "touch pad" grounded LED to light but not the the hard wired LED's. If nothing else, it will provide Mike with some more lab time for entertainment purposes.
-
Actually, I think you need two more neon lamps. Hot-neutral and hot-ground. A disconnected ground or neutral will not trigger a fault condition if you just use a neon on each wire.
yup and these could be cheaper LEDs but, but I wouldn't want them too bright to make the neon reporting harder to see.
My suspicion is that it won't be as susceptible as some NCVT are since it does draw some current. Perhaps the hot-neutral and hot-ground lights could be ballasted to draw the max current the neon can handle. Then a high percentage of the ghost voltage would likely cause the "touch pad" grounded LED to light but not the the hard wired LED's. If nothing else, it will provide Mike with some more lab time for entertainment purposes.
Yup some more bench time is indicated, but this seems like a promising direction IMO. Sorry I can't help with more than suggestions, until I get some parts to play with on my bench.
I suspect Mike will have this all dialed in by then. :'(
JR
-
I was thinking "touch pad grounded neon", but my fingers typed LED.
The next generation would use phototransistors to sense the LEDs and neons connected to a microprocessor powered by harvested AC power that would send a status text to your smart phone. So there is still work to do.
-
The next generation would use phototransistors to sense the LEDs and neons connected to a microprocessor powered by harvested AC power that would send a status text to your smart phone. So there is still work to do.
Aaaaaaaaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhhhhhh...... :o
-
I have been developing embedded microprocessor solutions for over a decade and while i have scratched up some schematics for an embedded approach, I believe I might even be able to do it without neon lamps or a touch contact (at least for a smart outlet strip with one or more products plugged in that could serve as an environmental ground reference before being powering up.) That said the market for a full bells and whistles outlet/wiring tester is more than I would ever consider. Hopefully some real test equipment makers are lurking here and taking notes in case we stumble upon a good idea or two. .
I really like the KISS approaches. GFCI with stinger cap, a handful of neon lamps in a simple tester, etc.
Even for the bootleg tester I'd rather use an audio sniffer and human judgement to troubleshoot wiring than try to accurately predict all the possible scenarios for a micro to resolve.
JR
PS: Yes I know you were kidding even without emoticons.. 8)
-
The next generation would use phototransistors to sense the LEDs and neons connected to a microprocessor powered by harvested AC power that would send a status text to your smart phone. So there is still work to do.
In much the same way as modern technology now allows us to hold a pencil like stylus device to actually write and draw onto a flat surface!
Steve.
-
In much the same way as modern technology now allows us to hold a pencil like stylus device to actually write and draw onto a flat surface!
Steve.
The parallel story I heard was the millions spent by NASA developing the space pen to write in a absence of gravity. The Soviets opted instead for a pencil.
frank
-
Simple devices are often the best solution-I was kidding about the second generation. Bench testing is the best verification, but it seems that a 5 light tester would give a comprehensive test of an outlets wiring scheme. To be truly comprehensive you need to do load testing-but I would like to have a tester like this is all of my vehicles and tool kits.
I noticed a 3 light tester with a GFCI test function priced at $2 more than a basic 3 light tester. That is just a resistor and a cheap switch for the extra cost. If the 5 light can be kept in the same ballpark and become the standard tool for testing it should be a significant improvement in safety.
For whatever reason I can't use emoticons with a quick reply on my ASUS tablet.
-
OK, I found a cheap source of neon bulbs in colored (coloured*) holders with built-in ballast resistors. So for $20 I can get 6 of each color for experimentation. So let's consider lamp colors for the 4 or 6 light touch tester. I could make the top half of this tester the traditional Amber-Amber-Red sequence, where you're looking for two yellow lights and no red light, then add three more neon bulbs on the bottom row connected to the H-N-G lines and a touch panel. Would I make those colors Green (Hot), Red (Neutral) and Red (Ground). That way any "Red" light indicates a problem, but Amber/Amber/Off on the top row plus Green/Off/Off on the bottom row indicated proper receptacle wiring. And a Red light on the Touch section while everything else is OK indicates an RPBG condition. Seems like a pretty definitive test to me.
I'm not sure about the relative brightness of the Red, Amber and Green lights, so maybe they should all be Amber and Red. Guess I won't know until I try.
JR, I can build two of these at the same time and send you one to try out if you like. That way we can compare notes.
* Here's a US to UK translation chart for Steve Smith and our other friends across the pond. I'm not sure who's spelling is correct, but I do know that we drive on the "right" side of the road here in the US.;D
http://www.oxforddictionaries.com/us/words/british-and-american-spelling (http://www.oxforddictionaries.com/us/words/british-and-american-spelling)
-
:'(
OK, I found a cheap source of neon bulbs in colored (coloured*) holders with built-in ballast resistors. So for $20 I can get 6 of each color for experimentation. So let's consider lamp colors for the 4 or 6 light touch tester. I could make the top half of this tester the traditional Amber-Amber-Red sequence, where you're looking for two yellow lights and no red light, then add three more neon bulbs on the bottom row connected to the H-N-G lines and a touch panel. Would I make those colors Green (Hot), Red (Neutral) and Red (Ground). That way any "Red" light indicates a problem, but Amber/Amber/Off on the top row plus Green/Off/Off on the bottom row indicated proper receptacle wiring. And a Red light on the Touch section while everything else is OK indicates an RPBG condition. Seems like a pretty definitive test to me.
I'm not sure about the relative brightness of the Red, Amber and Green lights, so maybe they should all be Amber and Red. Guess I won't know until I try.
JR, I can build two of these at the same time and send you one to try out if you like. That way we can compare notes.
* Here's a US to UK translation chart for Steve and our other friends across the pond. I'm not sure who's spelling is correct, but I do know that we drive on the "right" side of the road here in the US.;D
http://www.oxforddictionaries.com/us/words/british-and-american-spelling (http://www.oxforddictionaries.com/us/words/british-and-american-spelling)
Sounds like a plan to me.
-
:'(
Sounds like a plan to me.
Steve, should I build one of these for you to experiment with as well? I'm assuming I don't need to get any legal waivers signed in case you electrocute yourself... ;D
-
OK, I found a cheap source of neon bulbs in colored (coloured*) holders with built-in ballast resistors. So for $20 I can get 6 of each color for experimentation. So let's consider lamp colors for the 4 or 6 light touch tester. I could make the top half of this tester the traditional Amber-Amber-Red sequence, where you're looking for two yellow lights and no red light, then add three more neon bulbs on the bottom row connected to the H-N-G lines and a touch panel. Would I make those colors Green (Hot), Red (Neutral) and Red (Ground). That way any "Red" light indicates a problem, but Amber/Amber/Off on the top row plus Green/Off/Off on the bottom row indicated proper receptacle wiring. And a Red light on the Touch section while everything else is OK indicates an RPBG condition. Seems like a pretty definitive test to me.
I'm not sure about the relative brightness of the Red, Amber and Green lights, so maybe they should all be Amber and Red. Guess I won't know until I try.
JR, I can build two of these at the same time and send you one to try out if you like. That way we can compare notes.
Thanks but it would only irritate me to see how many of my outlets are reverse polarity.... AFAIK I don't have a single grounded outlet in my house. I had to rig up a bootleg ground outlet fixture to test that my GFCI stinger worked.
Feel free to involve someone else who is actively working in live sound and will be exposed to different venues so he can give it a proper real-world test.
BTW I believe I can buffer the touch contact (with more parts) and then the impedance of the test lamps can be dropped making it easier to ignore ghost currents, but the extra parts add more complexity and perhaps failure vectors, so not KISS.
JR
* Here's a US to UK translation chart for Steve Smith and our other friends across the pond. I'm not sure who's spelling is correct, but I do know that we drive on the "right" side of the road here in the US.;D
http://www.oxforddictionaries.com/us/words/british-and-american-spelling (http://www.oxforddictionaries.com/us/words/british-and-american-spelling)
I once asked the editor of a british sound magazine if the "buss" spelling was a British affectation. He was offended and declared "bus" the proper british spelling too. 8)
-
Some of the British words in that British - US spelling thing are wrong!
Steve.
-
Some of the British words in that British - US spelling thing are wrong!
Steve.
That's too funny... ;)
-
Steve, should I build one of these for you to experiment with as well? I'm assuming I don't need to get any legal waivers signed in case you electrocute yourself... ;D
If you would, I would help with testing. I don't do a lot of audio in unknown locations-but I do get into plenty of commercial/resi and even some industrials that have questionable wiring especially given the relatively recent licensing/inspection requirement around here.
Would a signed waiver do any good? If I get electrocuted, I won't be concerned about $$.
-
If you would, I would help with testing. I don't do a lot of audio in unknown locations-but I do get into plenty of commercial/resi and even some industrials that have questionable wiring especially given the relatively recent licensing/inspection requirement around here.
Would a signed waiver do any good? If I get electrocuted, I won't be concerned about $$.
Stephen, Mike
Given Stephen is across the pond (correct?) would the tester have to be any different (other than plug) for EU use/testing? (120vs220)
frank
-
Would a signed waiver do any good? If I get electrocuted, I won't be concerned about $$.
Steve, of course I was kidding about the wavier. If I kill you, I'm going to kill you real dead. ;D
But seriously, I would never send one of my test gadgets to the masses for review, only to people I trust. You're on a very short list of those I think would be able to perform testing of these devices safely.
-
I realize I am flip flopping on this, and while I like the KISS neon lamp approach, the more I think about it, and Mike's comments about ghost currents, I am revisiting my buffered touch contact.
The bad news is I still have to buy parts... (I need some 350V breakdown transistors for 120v mains), but the good news is the LED loads can be lower impedance to ignore the ghosts, and will more accurately indicate the no-touch state of both or all three LEDs on, if ground connection is present and the touch contact is floating. If ground is open only the line and neutral will light up when idling. When touched the properly wired ground and neutral LEDs will go out, or stay lit and line LED go out if RPBG.
The input to the transistor buffer can use 50-100k resistors in series with the bases, so even a shorted transistor would generate harmless single digit mA of current to the touch node.
Of course this is hypothetical and waiting for that same parts order for me to confirm (I'm still not ready to place my parts order). This will he harder to DIY with a bunch more parts but is not heavy lifting for a commercial tester using SMD components.
JR
-
I realize I am flip flopping on this, and while I like the KISS neon lamp approach, the more I think about it, and Mike's comments about ghost currents, I am revisiting my buffered touch contact.
If the neon bulb layout works well enough but we want more brightness, it would be simple enough to use each neon bulb ito trigger a photo-transistor which in turn would drive an LED. That would give you many hundreds of volts of isolation on that side of the circuit, and the ballast resistors could be high enough to reduce touch plate "shock" current to sub-milliamp levels if we want.
-
If the neon bulb layout works well enough but we want more brightness,
My brightness concern is when neon lamps are connected to each other but the common lead is not probed, so we effectively have a voltage divider. This suggests the line lamp will get >60VAC and the ground-neutral lamps will get <60VAC. Some neon lamps may not like <60V.
it would be simple enough to use each neon bulb ito trigger a photo-transistor which in turn would drive an LED. That would give you many hundreds of volts of isolation on that side of the circuit, and the ballast resistors could be high enough to reduce touch plate "shock" current to sub-milliamp levels if we want.
My concern is:
A) wimpy indication when contact not touched (this all lamps on "idle" indication confirms lamps and tester are functional, power and ground are present).
B) ghost or phantom leakage currents in a floating ground lead (I've measured fractions of a mA) might be enough to illuminate a neon lamp. (Ghost voltage could be high enough even if ghost current is low. Lower impedance lamp circuitry could absorb ghost currents without false indications).
Of course I have yet to prove that my buffer idea even works. For RPBG connection my buffer PS is swinging 120VAC so buffer may saturate at extremes. This could impact display quality, input impedance would still be the input resistance so safe
Of course I still like the KISS neon lamps too. The ghost issue may be manageable with some shunt resistance, while that increases potential touch pad current during a fault (RPBG) condition.
JR
PS: I don't know if there are any special concerns about the frequency of neon light to effectively excite opto-osolators. Apparently there is an old classic guitar effect that used a neon lamp and LDR so perhaps light is just light. My inner engineer is channeling Missouri, wanting to be shown that specific components work together but this is not important. Normal mode brightness is not my concern.
-
My brightness concern is when neon lamps are connected to each other but the common lead is not probed, so we effectively have a voltage divider. This suggests the line lamp will get >60VAC and the ground-neutral lamps will get <60VAC.
If there is too much cross-talk between the bulbs, my plan would be to add diodes in series with the ballast resistors which should stop the back-flow current you're referring to. Of course, only one side to the neon bulbs will light since it's only seeing half of the AC cycle.
-
If there is too much cross-talk between the bulbs, my plan would be to add diodes in series with the ballast resistors which should stop the back-flow current you're referring to. Of course, only one side to the neon bulbs will light since it's only seeing half of the AC cycle.
You will notice when I don't have parts so I can melt solder, I spend too much time over thinking stuff.
Yes, steering diodes will prevent lighting at idle. What I like about a lower voltage lamp system is that they can serve dual purpose, to indicate power is present, ground is connected, and that the tester lamps are all good.
I think I can overcome my frustration about not being able to bench test this. IIRC Some hi-efficiency LEDs are visible down to low single digit mA range. So I could make my LED based tester, scaled down to a couple mA without the buffer.
No more excuses, if you don't hear a report back from me, it means I stuck my fingers in an outlet. ;D
JR
-
IIRC Some hi-efficiency LEDs are visible down to low single digit mA range. So I could make my LED based tester, scaled down to a couple mA without the buffer.
I think you might be right. There's a variety of low-current LEDs rated for 2mA current draw at full power. That's right in the range you're looking for.
http://www.vishay.com/leds/low-current/
-
I think you might be right. There's a variety of low-current LEDs rated for 2mA current draw at full power. That's right in the range you're looking for.
http://www.vishay.com/leds/low-current/
If I add 100K build-out resistors and steering diodes these might just work in place of Neon bulbs for my 6-light tester. I'll have to compare brightness.
-
If I add 100K build-out resistors and steering diodes these might just work in place of Neon bulbs for my 6-light tester. I'll have to compare brightness.
Good news bad news... Using my decades old LEDs I had laying around, they work as expected to confirm power present and ground present (on my bootleg rig), but.... even running <2 mA touching the common node, does not turn off the ground/neutral LEDs. Even if I lick my fingers I am not enough of a current sink to shunt off the other LEDs.
Need to retest with steering diodes in series with the LEDs. To see if I can get an indication from touching without the shunt path to other lamps.
I can confirm the power present and ground connection with additional LEDs, but would lose the lamp self test feature.
JR
-
OK, success kind of. Using my decades old LEDs, and 2mA to real ground resistor current limit, with steering diodes I can just see a very slight glow in my neutral LED.... Which confirms what I already know, that this outlet is miswired.
perhaps I need to repeat with just a singer cap in series sized for more current worst case....
JR
[edit] bummer now I can't recreate that first weak result.
Another concern about using a human for the touch reference, the human is probably more like a capacitor than a resistor (actually both depending on clothes-footwear). With steering diodes, the cap portion would probably get charged up to voltage and stop drawing current.
I am back to thinking buffer, but need to get some modern LEDs and buy some damn parts....
OK according to WWW human body is only 100-200pF so 13M Ohm at 60 Hz... Resistance can be lower if body is grounded but that can not be counted on not to mention capacitance needs to be relative to something too.
I'm leaning toward MOSFET buffer now...
With my VOM I measure 40 VAC using my body as a ground, so my body impedance to ground (neutral) is 2x the VOM circuitry input impedance.
JR [/edit]
-
FWIW, I routinely wear EH rated footwear-don't count on it ever, but I will rarely be "grounded" when using a tester.
JR, it seems a 2 light tester should work just fine in your home (IF your receptacles are polarized-if not polaarized then testing is probably pointless). Just thought I'd give you something else to consider:)!
-
FWIW, I routinely wear EH rated footwear-don't count on it ever, but I will rarely be "grounded" when using a tester.
Steve, the 4th "hot-ground" bulb on my test last week was done standing on a wood floor in timberline boots, so I wasn't grounded but still was able to light the bulb via my capacitive connection to the earth. Of course, none of these proposed testers are perfect, but should at least warn the technician or electrician that something is wrong that requires further testing.
-
Just received my Neon handle screwdriver testers from China. IIRC the cost was less than $2 each including shipping. As you can see, they actually work pretty well in a dimly lit room, but you wouldn't be able to see the Neon bulb in a bright room or outside in the sun. Still, an interesting test and confirmation of an old-school voltage tester.
-
Just received my Neon handle screwdriver testers from China. IIRC the cost was less than $2 each including shipping. As you can see, they actually work pretty well in a dimly lit room, but you wouldn't be able to see the Neon bulb in a bright room or outside in the sun. Still, an interesting test and confirmation of an old-school voltage tester.
The interesting thing is that this "$2 old school tester" is actually a very good companion to the 3 light tester to detect RPBG. It is less susceptible to false positive than a NCVT though an audible tester does have advantages in bight light. Haven't used one in a while-need to get one though.
-
The interesting thing is that this "$2 old school tester" is actually a very good companion to the 3 light tester to detect RPBG. It is less susceptible to false positive than a NCVT though an audible tester does have advantages in bight light. Haven't used one in a while-need to get one though.
Yeah, a few of my electrician buddies showed me how to use these 50 years ago when I was a young pup, and my dad always had one in his toolbox which I used when I couldn't find a meter. So except for the dim light issue, they really are pretty useful.
So, why did they fall out of favor and common use? Anything in code that makes them a violation to use? Have there been any deaths or injuries due to their use? Remember, this is about as simple as you can get, a neon bulb and a resistor connected to the screwdriver blade on one end and the brass touch button on the butt of the handle.
Here's where you can get them for less than $2 each, including shipping: http://www.ebay.com/itm/100-500V-Screwdriver-Voltage-Tester-Neon-Bulb-Electric-Tester-Pen-Probe-BK43-/261682795328?pt=LH_DefaultDomain_2&hash=item3ced829340
-
Why did they fall out of favor? My suspicion is that for a bit more you can get a 3 light tester that has a legend printed on it-in other words, requires no brain power to use.
The "code" doesn't address work methods/tools. NFPA 70E does, but I doubt there is anything that precludes using them. I don't have a copy of 70E, but I need to get one for a project so I'll do little "lite" reading.
The ones I remember had two flexible leads so you could probe 2 leads of a receptacle with them-to use your body as a ground you just folded one lead back into your hand. A practical consideration for future receptacle testing is the TR receptacle which is required in resi, but cheap enough it makes sense anywhere children will be present. That is actually one of the things that pushed me away from just using a meter to verify a receptacles wiring, since it is very difficult to defeat the mechanism without damaging it.
So, while an old school neon with a 3 light will work in a lot of older buildings, a purpose built 4/6 light tester makes a lot of sense going forward.
-
I don't have a copy of 70E, but I need to get one for a project so I'll do little "lite" reading.
Pun Alert!!! :o
-
I remember something like this from back when I was a kid...
(http://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Neon_Test_Lamp.jpg/800px-Neon_Test_Lamp.jpg)
I second the vote that this makes a versatile addition for troubleshooting mains wiring.
JR
PS: I am probably going to go ahead and order some parts this weekend... I'd like to mess around with neon lamps myself (to check out the ghost issue), and the 400V mosfets I need to make my buffer are the same parts I am going to use to make my solid state fuse, and to generate a switched test load to test for bootleg, so not crazy to bring them in. I'll go ahead and order a few 0.15uF "Y" caps to make my stinger GFCI.
PPS Even tho it looks like a stinger cap GFCI, and neon lamp screw driver may be all we need. KISS
-
PPS Even tho it looks like a stinger cap GFCI, and neon lamp screw driver may be all we need. KISS
You know, it would be really easy to come up with a little contact button with a neon bulb that could be mounted right on a guitar chassis or even the guitar itself. Touch the button with your finger, and if the lamp glows, then the chassis or instrument is electrified. How's THAT for simple?
-
Or we could make a futuristic looking glove with neon bulb built into the finger.. the muso just touches stuff with it, and if his glove finger lights up, danger Will Robinson. :-)
JR
-
Or we could make a futuristic looking glove with neon bulb built into the finger.. the muso just touches stuff with it, and if his glove finger lights up, danger Will Robinson. :-)
JR
Which finger??? ;D
-
Will the neon lamp light if the player is touching the guitar and the touch pad? My guess is no-and that would be an easy mistake many would not understand.
-
I told myself I was going to finally order parts last weekend, but noooo, I've changed the design twice since then... I am now about ready to stick a fork in it... (parts are ordered).
I now have the cheapest DIY (aka door #1) using a stock GFCI with a Y cap in place of the ground lead. My next better version (door #2) Uses a stock GFCI but with a relay in series with the ground lead. The relay coil can be powered by the GFCI output side, so if the GFCI trips the relay opens up the ground too. Then for icing on the cake I sense current in the ground lead and use that to force the GFCI to trip (an opto-FET) with the input side LED in parallel with a ground resistor (couple hundred ohms), with it's isolated secondary connected to imbalance the GFCI will trip the GFCI at X mA... This way I can trip both with less than 5mA. A couple hundred ohms in the ground is lower Z than a 0.15uF Y cap except for at very HF... I could use a cap and resistor in parallel since any fault will likely be at 60 Hz but ground noise can be anywhere. (I'm still waiting for feedback on how quiet the 0.15uF is).
I ordered some neon lamps too so I can mess with them, and some 400V mosfets so I can make a buffer for a lower impedance touch sensor, while the KISS unbuffered approach still looks attractive.
Mo lata...
JR
-
The dangers of an active mind, idle time, and a house full of randomly wired outlets. Oh my! ;)
-
So, why did they fall out of favor and common use? Anything in code that makes them a violation to use? Have there been any deaths or injuries due to their use? Remember, this is about as simple as you can get, a neon bulb and a resistor connected to the screwdriver blade on one end and the brass touch button on the butt of the handle.
So the only thing relating to this I can find in NFPA 70E is that if there is a risk of entering the "restricted approach boundary" the PPE for shock protection must be worn. "Restricted approach" for less than 150 vac is "avoid contact". I suppose that one could argue that there would be a risk of touching the screwdriver blade/shaft so insulating gloves would be required-which would defeat the touchpad. A plug in tester similar to the 3 light tester would not share that risk-so as long as it could be shown that no shock hazard exists (UL listing??) from the touch pad then it should be acceptable.
-
I suppose that one could argue that there would be a risk of touching the screwdriver blade/shaft so insulating gloves would be required-which would defeat the touchpad. A plug in tester similar to the 3 light tester would not share that risk-so as long as it could be shown that no shock hazard exists (UL listing??) from the touch pad then it should be acceptable.
My $2 neon screwdriver voltage tester has a clear plastic insulating sleeve over most of the shaft, with only the flat tip metal exposed. So not really dangerous unless the neon bulb and resistor both short out at the same time. There's just not much that can wrong with the KISS design.
-
Here is some interesting technical info on neon lamps. I didn't know there were so many options-different colors and even high brightness. Even the high brightness have a 20,000 hour average life-that a long time to hold a test screwdriver in a receptacle!
http://www.intl-lighttech.com/products/light-sources/lamps/neon
-
Here is some interesting technical info on neon lamps. I didn't know there were so many options-different colors and even high brightness. Even the high brightness have a 20,000 hour average life-that a long time to hold a test screwdriver in a receptacle!
http://www.intl-lighttech.com/products/light-sources/lamps/neon
Cool....
And they used to use neon bulbs for logic elements. Here's a neon bulb logic circuit driving Nixie tubes, which are also neon.
http://wwwhome.cs.utwente.nl/~ptdeboer/ham/neonclock/
-
I vaguely recall my (older) brother building a gadget back when he was in HS. He called it a "foo counter" and it was a bunch of components with resistors, caps and neon lamps, that would randomly blink on and off.
Thinking about it now, I suspect it was a large voltage DC supply (perhaps the line rectified) with resistors charging up caps. The caps also had neon lamps in parallel across them. When the caps charged up high enough voltage to break down the neon gas the lamp would flash and discharge the cap. The randomness of threshold voltages, cap values etc, resulted in random blinky lights. As my brother described it to me "foo"s were invisible rays from outer space and the lights would flash every time one passed through the device.
I knew it was a joke but never bothered to figure out how it works (or I think it worked) until now.
JR
-
I vaguely recall my (older) brother building a gadget back when he was in HS. He called it a "foo counter" and it was a bunch of components with resistors, caps and neon lamps, that would randomly blink on and off.
Sort of like this? https://www.youtube.com/watch?v=lph5zAdcwi8 (https://www.youtube.com/watch?v=lph5zAdcwi8)
-
Sort of like this? https://www.youtube.com/watch?v=lph5zAdcwi8 (https://www.youtube.com/watch?v=lph5zAdcwi8)
As I recall not as many lights on steady... mostly off but random short flashes on... but this was more than 50 years ago so my memory is not perfect.
======
I got my parts in today so now I have some neon bulbs to play with.
JR
-
Mike et al okay I live in 240V world but those little neon screwdrivers were banned from my work place a good while ago for 2 reasons 1) it was possible to get a shock if they were wet,or if the insulation got cracked, I personally got stung by the thing being damp and I tell you it hurt :'(. The other reason was a general ban on single pole testers because guys were putting the thing into the live contact if it didn't light then the circuit is dead right? eh no not when the neuutral or ground are live hence the insistance on 2 pole connectors.
We use this thing http://www.socketandsee.co.uk/details.asp?categoryid=197&ProductID=11&Product=Socket & See PDL234 Plus Part P Loop Testing Kit nowadays, and though it won't directly show a hot ground it will refuse to do a loop test which warns you of ground issue that you can then check with a meter.
-
Mike et al okay I live in 240V world but those little neon screwdrivers were banned from my work place a good while ago for 2 reasons 1) it was possible to get a shock if they were wet,or if the insulation got cracked, I personally got stung by the thing being damp and I tell you it hurt :'(. The other reason was a general ban on single pole testers because guys were putting the thing into the live contact if it didn't light then the circuit is dead right?
And neither of this is the fault of the tool. No matter the simplicity or complexity of your tool of choice there are 2 very important prerequisites to using it.
First, you must understand how to correctly use it-this includes knowing the safety hazards involved.
Second, you must understand its limitations.
The limitation of the complex tester you mentioned is essentially (if I understand correctly) the same limitation if the 3 light tester not being able to discern a RPBG.
No tool is foolproof (guess what happens if you use a damp DMM probe in a receptacle?)-and as this discussion shows, the less user knowledge the tool design demands, the more difficult it is to design and the more complex the design. The more complex the design, the more likely it is to fail at some point.
With a thorough understanding, it is possible to make all of the tests necessary to verify a receptacle with a DMM (you can usually even use your body as a ground and discern a RPBG. The 3 light tester along side the neon screwdriver is a more convenient tool.
-
I am still working on this and ideally the human contact is not necessary (so far it still is). It looks like I can limit the sense current to micro-amps not milli-amps, but eliminating it entirely would be even better.
but not today.
JR
-
OK my parts arrived to make an improved higher impedance touch buffer... I have one project on the bench ahead of this. Ideally I would like to make this not require a human touching it but that might be easier to build into a smart outlet strip than a small hand held tester. If I can get the sensitivity high enough there may be no need to touch anything.
No promises... only hopes..
JR
-
Thanks for the update, JR. I've been following this thread with anticipation and am excited whenever there are updates.
This could be a very handy gadget for hotel world...
-
In the meanwhile you can do a lot with the simple neon lamp probe.
Working on my other project today but the outlet tester is still on my bucket list. 8)
JR