towing lights 24v to 12v

[gumpy]

If you feel like building something, I've assembled a whole slew of options for converting 24V to 12V on my site:

  http://bus.getdave.com/Docs/12Von24V/

While there is some good info on how to obtain 12v from a 24v bus on your site, it appears that it doesn't address the main issue of toad wiring, which is that most buses have separate turn and stop signals, while most toads and trailers have combined stop and turn lights. That's where the relay system comes in. It combines the separate stop and turn signals on the bus into a single output which goes to each side of the toad to drive the single stop/turn light.

craig

[rv_safetyman]

If you have access to the March 09 issue of BCM, there is a very detailed article on the subject.  I included Craig's and Jack' diagrams in the article and also gave resources for the parts.

The "Bosch type" mini ISO relays all have the same connection configuration.  However, there are differences with some having built-in diodes.  I would recommend the latter for the application.

A bit later today, I will post a PDF on these relays on my website.

Jim

[Ed Hackenbruch]

I bought a little box called BriteLights, made by Roadmaster, from Camping World for about $29 if i remember right. Has 4 wires on one side and 2 on the other. Even i was able to figure out from the directions how to hook it up. Been using it for 6 years now with no problems.

[rv_safetyman]

Ed, does that unit work with 24 volt to 12 volt systems?  I used some aftermarket systems and they did not last very long.  I don't know if you remember, but I was writing the article when we were staying with you last year.  I had the parts delivered to your address and built the system shown in the March '09 issue right under your nose

The systems that use "commercial" grade relays are quite a bit more robust and about the same cost.

I did post the relay data sheet I created at:  http://www.rvsafetysystems.com/Relay%20data%20sheet.pdf

Jim

I just looked at my article, and I used Craig Shepard's and Sean Welsh's diagrams.  The Welsh diagram shows the wiring for the relays with diodes.  Jack Conrad was also a great help on the article.

The following is pasted from that article:

Digi-Key (www.digikey.com)
Tyco, part number PB682-ND (12V with diode)
Tyco, part number PB684-ND (24V with diode)

Del City (www.delcity.net)
73986 (12V with diode)
73570 wired socket only

[daveola]

..which is that most buses have separate turn and stop signals,..

Ah, my bad, that's what I get for glossing over the board.  Sorry to clog up the lines. 

Maybe at some point I'll put up a simple relay diagram to show how to hook that up.

[Ed Hackenbruch]

Jim, you got me wondering!  All of my lights except the headlights are 24 volt.  i dug out the card that the Brite-Lite came on and it does not say anything about voltage and yet it works just fine. i do have some relays that the PO used to run his Jeep lights thru but did not work with my Jeep. I figured one of them was bad, ( i would touch the brake pedal and lose all of the lights) so i bought the box and hooked it up and it worked.   Don't have the time right now to check this out more as we are busy getting ready to leave in a few days.  This is made by Roadmaster, part # is 732.  Maybe somebody can look it up and tell me why it can not work!

[gumpy]

Jim, you got me wondering!  All of my lights except the headlights are 24 volt.  i dug out the card that the Brite-Lite came on and it does not say anything about voltage and yet it works just fine. i do have some relays that the PO used to run his Jeep lights thru but did not work with my Jeep. I figured one of them was bad, ( i would touch the brake pedal and lose all of the lights) so i bought the box and hooked it up and it worked.   Don't have the time right now to check this out more as we are busy getting ready to leave in a few days.  This is made by Roadmaster, part # is 732.  Maybe somebody can look it up and tell me why it can not work!

Boy, you got me.  I just looked at the instructions (http://www.roadmasterinc.com/pdf/25-1640-04.pdf), and I don't see any way that it should work. If you're running your 24v brake and turn signals into it, it should be putting out 24v combined signals (if it doesn't burn up). They don't actually ever say it's for 12v or if 24v will work, but without a 12v supply, I would think the outputs would be equivalent to the input voltages. Maybe it's more sophisticated than that, but for $40, I doubt it.

[Lin]

Wait now, I thought that this device was just for solving the brake light/turn signal problem only after the voltage reduction, not the it would do both. 

[Jerry32]

I built craigs device and installed it in the rear junction box and it does it all to convert 24 to 12 and to mix or correct the signals from bus to towed Jerry

[BJ]

I purchased a set of magnetic lights from uhaul then changed the pigtails and inners from a pair of 24 volt lights now making them 24 instead of 12.  Works great and easy to do..I set them on the fenders of the trailer with the maginets holding them in place.

[rv_safetyman]

Ed, I recall that we did a bunch of looking at your old relay system.  It was kind of hard to get a good look at them, but I think that we figured out that somehow the relays gave you 12V to the toad.  If you hooked up the new converter to something in that old relay system, you might be working with the correct voltage. 

As Dallas said, the converter you bought does not address the difference in voltage. 

If you have a voltmeter, you should check the output at the connection plug.  Somehow it must be OK or you would have a bulb problem.

Jim

[zubzub]

RV safety man I give you the award for posting the obvious.  I have had to re learn all that repeatedly over the years, 'cause I never write it down, I know how to figure it out when I have a relay in front of me, and then I forget again.  Every so often I have gone online to search a nice clear explanation  and yours is by far the clearest I have ever seen.  I think I'll print a copy and post it to my forehead, so everyone else can know this.  BTW I'm joking around but I'm serious, all to often, we (myself included) presume the rest all understand the basics of a system, it's great to have the basics spelt for those not yet in the know.  Cheers, Patrick

[rv_safetyman]

Patrick, thanks.  I have been working on an update to that document to include the same relay with a built in diode.  Costs about the same and really prevents some problems in critical circuits with voltage in-rush problems. 

I will get that done today and post it on the site.  Will come back with a reply when I get it done.

I am like you, I have to rethink the relay each time I use it, and I use a bunch of them.  That is why I tried to make the document as simple as possible -- so that I could understand it

Jim

[rv_safetyman]

Sorry -dual post

Jim

[Melbo]

Here is another source for a prewired relay socket

http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-26-1942-/26-1942

Melbo