Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Chris Hindle]

That is absolutely correct.  The Dave Rat/Sound Tools XLR sniffer can't detect that either when used with ordinary phantom power.  However, it can if you use the battery powered sender unit with it as it puts two different voltages on pins 2 and 3.  I could also do that with mine but decided not to as in reality, as you point out, cables don't re-wire themselves, they just short out or go open circuit. The swapped connections it does indicate are just extras which might be useful sometimes.




Steve.

I have a couple of the RAT sender/receivers.
At the show, I don't really care what's wrong, just that the cable is "bad"
If I don't see 3 green, a knot get's tied at the end of the cable, and it is put aside for some shop time.
I always wondered what was in the RAT tool.
Thanks for sharing.
Simple, but brilliant all at the same time.
Chris.

[Steve M Smith]

I always wondered what was in the RAT tool.

Just to be clear, this isn't a copy of the Sound Tools device (I wouldn't do that).  Mine is different.  You can find the Sound Tools circuit by doing a patent search.

I actually think mine is more logical.  The error codes can be remembered quite easily.




Steve.

[Chris Hindle]

Just to be clear, this isn't a copy of the Sound Tools device (I wouldn't do that).  Mine is different.  You can find the Sound Tools circuit by doing a patent search.

I actually think mine is more logical.  The error codes can be remembered quite easily.




Steve.

Hi Steve.
Sorry, I didn't mean to imply anything.
YOUR design is simple, and brilliant.
I can't imagine the business end of the RAT tester is a lot different.
Chris.

[Steve M Smith]

Sorry, I didn't mean to imply anything.

No problem. I wasn’t presuming that you might have thought that. I just thought I should generally point out that it wasn’t a copy.




Steve.

[Abhinav Patankar]

Hi Steve,

I'm a live sound engineer based out of india. During this lockdown time, I have been trying to build a prototype of the XLR sniffer. After days of searches on the internet I was finally thrilled to see the circuit daigram posted by you. Just so you know I'm a complete dummy when it comes to electronics and components, though I have been doing a lot of reading in the down time to understand the working of different components. I was wondering if you could guide me in building this prototype.

Here are few questions I had after studying your daigram(Please excuse me if you find some of them very stupid )

1. Are you using 5mm leds which work on 5V dc? And is this the reason you are using a 5v6 zener diode?
2. What if I were to use a 3mm led with forward voltage of 2-2.1V, would the zener diode configuration change to 2v4?
3. Irrespective of whichever led  I end up using does the value of my resistor change? If yes how do I calculate that?
4. Would the circuit change if the applied voltage changes to 12V?
5. Lastly, How would my connections change if I were to use a 3 PIN bi colour 5mm led? as in where do i connect the common terminal?

I kindly request you to please guide me through this, as I have been stuck with question for days. Any sort of help would be very kind of you.
Thank you. 

Warm Regards,
Abhinav
+91 8805507035

[Steve M Smith]

1. Are you using 5mm leds which work on 5V dc? And is this the reason you are using a 5v6 zener diode?
2. What if I were to use a 3mm led with forward voltage of 2-2.1V, would the zener diode configuration change to 2v4?
3. Irrespective of whichever led  I end up using does the value of my resistor change? If yes how do I calculate that?
4. Would the circuit change if the applied voltage changes to 12V?
5. Lastly, How would my connections change if I were to use a 3 PIN bi colour 5mm led? as in where do i connect the common terminal?

1. They are 3mm LEDs. Red and green. Forward voltage is about 1.7v. The 5.6v zener is there so that if pins 2 and 3 are shorted, there is not enough voltage to light the LED with the zener in series. The other LED limits the voltage to 1.7v so no current can flow through the zener.
2. A higher forward voltage LED is fine, no need to change the zener. However, any zener from 1v to 10v will work. I used 5.6v as it is a standard value which I have a lot of.
3. The resistor value is not critical. 470R to 4K7 will be fine. The current is limited to 7mA by the 6K8 series resistors in any mixer's phantm power circuit. The tester doesnt need that resistor to work. It was added at Dave Rat's suggestion to prevent damage if accidentally plugged into DMX or Cue light system, or anything non standard.
4. It will work on 12v, but you need some resistance in series to pins 2 and 3. I suggest 2K2.
5. You cant use a 3 terminal LED. It needs to be the two terminal type with one LED connected one way and the other, reversed. Like this... [size=78%]https://www.digikey.com/products/en?mpart=LTL-14CHJ&vendor=160[/size]


For personal use only.


*** CONTACT ME IF YOU WANT TO USE THE DESIGN COMMERCIALLY ***




Steve.

[Steve M Smith]

If anyone is interested, this is my simple, single LED version. In a live situation, you just want to know good or bad. The LED will only light if all three conductors are good and there are no shorts.




Steve.

[Andrew Broughton]

If anyone is interested, this is my simple, single LED version. In a live situation, you just want to know good or bad. The LED will only light if all three conductors are good and there are no shorts.

Brilliant! Uses phantom, correct?

It looks like the only catch is that if pins 2/3 are shorted or swapped it would still show "good"?

[Mac Kerr]

Hi Steve,

I'm a live sound engineer based out of india.
Warm Regards,
Abhinav
+91 8805507035

Please go to your profile and change the "Name" field to your real first and last name as required by the posting rules displayed in the header at the top of the section, and in the Site Rules and Suggestions in the Forum Announcements section, and on the registration page when you registered.

Mac
admin

[brian maddox]

If anyone is interested, this is my simple, single LED version. In a live situation, you just want to know good or bad. The LED will only light if all three conductors are good and there are no shorts.




Steve.

When I was getting started in the early 90's I made a super simple phantom tester that was just a Switchcraft male XLR with a green LED between 1 and 3 and a red between 2 and 3.  I'd take off the strain relief boot and fill the inside of the connector with silicone to keep out dirt and junk.  The LEDs would still glow just fine in the translucent silicone.

I didn't know enough to add resistors or any of that "fancy" stuff.    Still worked just fine.  And it was so simple and basic I made a bunch of them so we could all carry one in our pocket and if we lost it we just grabbed another out of the bin. As Andy said, it didn't show pin 2 and 3 shorts or swaps.  I toyed with making a "sender" that would apply voltage to 2, 3, or both to test when phantom wasn't available and to show shorts and swaps, but honestly I just didn't find enough of a need for it.

In today's world I find myself needing to do a LOT less analog cable troubleshooting, so it's not as a big of a need. But it certainly was a handy thing to have back when we were dealing with hundreds of feet of wire and usually at least half a dozen connections on every input channel.

[ProSoundWeb Community]