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on-off-on "light switch"

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Steve-White:

--- Quote from: Bob Faulkner on February 25, 2023, 01:20:37 PM ---What I'm looking at with either the SPDT or DPDT are ON-OFF-ON toggles.  The SPDT appears exactly what I need.  Though, for a DPDT toggle, I would need to connect (using a jumper wire) the "2" load to the "1" load, in order to route the power from the second 12V service to the LED light.  Is "cross-connecting" of wires an acceptable practice?

Follow up question:  would there be any issues with having 2 x 12V batteries (independent of each other) sharing a common " - ", when one of those batteries is powering the LED light?   

--- End quote ---

That's exactly my point between single and double pole.  Without knowing the exact characteristics of the sources, you would do best with double pole and switch BOTH the ground and hot sides.  No jumpers needed.

WRT your question - is it separate batteries that won't be connected to a charging circuit then yes.  If charging is involved I wouldn't do it without seeing schematics of the charging system(s).

Bob Faulkner:

--- Quote from: Steve-White on February 25, 2023, 03:06:19 PM ---That's exactly my point between single and double pole.  Without knowing the exact characteristics of the sources, you would do best with double pole and switch BOTH the ground and hot sides.  No jumpers needed.

WRT your question - is it separate batteries that won't be connected to a charging circuit then yes.  If charging is involved I wouldn't do it without seeing schematics of the charging system(s).

--- End quote ---
Good point about the charging circuits.  One 12V battery will NOT be on any charging circuit.  The other battery will be on a charging circuit (but may not be charging all the time); this battery is in the cargo van (the engine battery), and would only be providing power (through the 7-way trailer connecting power cable) if the first battery (the non-charging battery) is depleted.  Our night time load-outs can take a few hours, and I don't like running lighting off the cargo-van battery for that long... which is why I installed a "dedicated" battery in the trailer to run the lighting.  But, if that battery runs out during a load-out, I would be able to switch to the van battery "at the flick of a switch".

The LED lights in the trailer were originally being powered by the van (via the 7-way trailer connector).  It's been like that for years, but is now being powered by a stand-alone 12V battery inside the trailer. 

I like the idea of having separate 12V power sources for the lights, but it looks like when connecting all the " - " together, this may introduce other issues.  Maybe I'm not fully understanding the electrical paths within a DPDT switch.  I'm learning about it from the Internet, but I haven't been able to find something that is specific for my need.

The previous suggestion from Art looks exactly right for my situation; but the connecting together of " - " I wasn't too sure about. 

My backup plan would be just to have another 12V battery available to replace the one in the van.  If a DPDT or SPDT toggle would work, I would rather opt for that solution.

Thanks.




Steve-White:
Pretty simple stuff Bob.  Just be sure it's all fused.  Lots of stories from the racing community on trailer fires with the ignition source being a battery.

With a backup battery that's not connected to the vehicle electrical system a SPDT will work fine.  Just connect the negative to the vehicle ground which will be the frame which is where the negative of the lights will end up being tied to somewhere in the circuit.

Inline fuse on the positive side of the battery is highly advised.

Jim Thorn:
Bob,

  The wiring diagrams you linked to may be a little confusing, because they show a commercial electrician how to wire two selectable loads to a single power source, and you're looking for two selectable power sources to a single load.  To an electrician, "L1" means incoming powerline #1, not "Load #1", so the labeling may be confusing, too.
 I've linked a diagram for using that DPDT switch for your situation.  Unless the cost of that switch is prohibitive, I would use DPDT for its sheer conceptual simplicity (and no splice required), but if you go with SPDT as others have mentioned, the link has a diagram for that, too.

Switch sketch

I hope this is helpful.

Jim Thorn


--- Quote from: Bob Faulkner on February 24, 2023, 12:59:21 PM ---Thanks again for the switch link!

My project is to supply power (12V) to a single strip of LED lights.  But, the power would be originating from 2 separate sources.  At any given time, the LED lights would receive their power from only 1 electrical source at a time.  Therefore, if one source of power is unavailable, I could switch (using the on-off-on switch) to the other power source for the same set of LED lights.  Also, I could power-off the LED lights by keeping the switch in the middle position.

I downloaded a Leviton "schematic" covering double pole switches.
https://www.leviton.com/en/docs/PK-93107-10-02-0D-W.pdf

On page #1 of the document (it's only 2 pages) under Figure #3, this looks like what I need... however, the schematic shows two loads, but I only need one.  From the schematics, looks like Circuit A can only power "load 1" and Circuit B can only power "load 2".

Question: Can the "load 2" be wired into "load 1" so that circuit "B" can power "load 1" when the switch is moved from Circuit A to Circuit B? 

Should I be looking at a completely different solution?

Bottom line...I'm trying to come up with a way to have a redundant power source for a single set of LED lights in my trailer.

Thanks.

--- End quote ---

Steve-White:
Try this one.  There are 3 negatives on one side of the switch and 3 positives on the other side.

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