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24v to 12v trailer adapter.

Stretch44875

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This is a long one, was even a longer day. Am towing my camper to haspin. Last year I used a 24v bulb in my magnetic towing light set. Had to rewire it because the 24v bulb elements are reversed from the 12v bulb.

I lost the 24v bulbs, and at 11.00 a piece from napa, they are not cheap. In a time crunch, so didn't want to order anything and have to wait. On the web, a couple of places offer them for 2.00 and less. Plus I would have to buy a second magnetic light set, that way I don't have to rewire my only set every time I used it on the deuce. (another 50 bucks.. GRRRR.)

I am not very familiar with electronics, so I called a couple of guys. Thought about adding a second set of lights in series to reduce the voltage, but the bulbs share grounds. Would end up with about 8 lights to get it to work!

So we ended up with some IC voltage regulators. They are good to 5 amps, and reduce voltages up to 30 volts to 12v. Expensive at 25 a piece. Bought 3, one for tail lights, one for left turn, and one for right turn. They ground through the case. Part # NTE933.

Made up a small box for them, so I could seal it. This is a first for me, so may not be to standard wiring! And you can see why I need a trailer plug.

Wired it up, and OMG, it works! Only thing is on hazard lights, only one side blinks. Think it needs a diode somewhere for that. Tail and blinkers work, haven't tried brake yet.

First pic is of plug, second one is lights, Third one I tried to show the back of the regulators, and wiring. Fourth one is the box I used. Still need to seal it up, and add cover over the regulators.

Feel free to point out what may need fixed yet, as I said, I am no expert at this.

Dennis
 

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cranetruck

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Good job Dennis!

These regulators have built-in over current protection and will shut down in case of a short circuit.
You have to consider the cold filament inrush current when working with incandescent light bulbs, it could be as much as 10 times the operating current. Possibly 10 to 15 amps for each bulbs used here.

The heat dissipated in each regulator will be about the same as is dissipated in the lamp bulb, so they will get hot. The way you mounted the regulators will help keep them cool. Too much heat will shut them down too.

The way you wired them should not require a diode for isolation, the bulbs are already isolated by the regulators. If one refuses to turn on as you say, it could be the inrush current shuttinig it down.
For a long term install, protective circuitry should be added. Look up application notes for the regulator and follow the advise given.
Can't believe the cost, though, $25/ea.. wow.
 

Stretch44875

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What kind of protective circuity are we talking about? No paperwork came with these. I have a link to a PDF on them.

I thought 25 was high, but they had them in stock, and I was in a rush.

http://www.hobbytron.com/NTE/specs/900to999/pdf/nte933.pdf

I didn't know about the cold current rush. I just looked at the specs on the bulbs for current.
Most of my trailers have just a single bulb, and maybe one clearence light. My camper has many clearence lights, but if I drive at night, I can use the camper battery to power them.

For those interested, the 24V bulb is # 1662.

Dennis
 
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Stretch44875

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Led's are cool, and would use them, but.... all my trailers are still regular bulbs. Want to be able to hook up and go no matter what I am pulling. May end up adding a bigger voltage regulator for the tail lights of my campers.
 
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jodka

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That's nice work. These are not criticisms, but just to consider the consequences and weigh the alternatives:

1. The 12V bulbs draw twice the current of 24v bulbs of the same power. That's ok if drawing more current does not exceed ratings and shorten the lifetime of the turn signal switch. Does it?

2. Why not use a power resistor in series with each bulb instead of the voltage regulators? Resistors are less expensive. And simpler. Glancing at the DigiKey catalog, looks like, depending on what style you wanted and whether you needed 50 or 100 Watt, you could find something between about $5.00 and $10.00/resistor.

3. What about powering 12 volt bulbs with a 24 Volt 50% duty cycle square wave? That has a few advantages over the voltage regulators or resistors:
A. Much less heat build up in the oscillator circuit than in resistors or the voltage regulator.
B. Little wasted energy.
C. Same current draw as 24V bulbs.
D. Price? Don't know. But power MOSFETs are pretty cheap and not much else should be required.
Downside: Much more time to design and fabricate than using resistors or voltage regulators.
 

mcinfantry

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i used it on a tow behind BBQ pit. the m715 was 12v, the deuce 24. i towed it last tailgate season and no probs. hell i gave it to the LA Natl guard (the BBQ pit and trailer) they are still using it!
 

Stretch44875

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Jodka
Sqare wave? oscillator? Got to remember who you are talking to! I have NO electronics training, just basic electricty, and a lot of reading. I do know what a square wave is, and oscillator, but have no knowledge of how to apply them to anything.

If I am thinking right, resistors would have to be sized to the bulb used, and I plan on using this setup on different trailers. Idea is to back up to any old civilian trailer, and plug in.

Sounds like the mosfets are the way to go, but I once again, I am not quite there on building this stuff.

Well, after ALL day of playing with the wiring, I found out that a short light set work great, and my 20 foot light set didn't. After much screwing around, I took the truck to the expert, otherwise known as Dad. :) Had some really goofy things happing, like touching a wire that wasn't connected to anything, but ran with the other wires, and having a light quit. Talk about weird. Turns out we had to add some capacitors to the wiring after the voltage regulators. They were making noise, and would pick it up from the wires over the 20 run of wire. Once those were in, everything worked great. Still need to finish fabing the box up, and get it water tight.


Dennis
 
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Stretch44875

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I like the light bar Kenny. Finally got it all together, had to install a larger box for the capacitors. No time for pics, too busy getting ready for haspin!

Dennis
 
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