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Open Roads Forum  >  Tech Issues

 > Homemade LED light "fixture"

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Harvey51

Alberta

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Posted: 06/29/12 11:01pm Link  |  Print  |  Notify Moderator

After replacing all the motorhome light bulbs with LED panels, I had a couple left over and made reading lights over the dinette with them. I just cut a piece of wood at an angle to aim the light, notched it so a switch I happened to have would simply push into place, and stuck the LED panel over top. I actually cut on the table saw a strip of wood long enough to make half a dozen of these lights.


Here it is in place under the cupboard hanging above the dinette seat.


I was very surprised that the LED strips got very hot! They don't do that when we are boondocking on battery power, as we always do when camping. The slightly higher voltage (about 1.5 V higher) of the converter running off AC doubles the current drawn (from 150 mA to 290 mA). If I wasn't a habitual boondocker, I would be adding a resistor or a couple of diodes in series with the LED panels to drop the voltage a bit and avoid that heat which must be very hard on the LEDs. Actually I suppose there is little point in using LEDs if you are usually plugged in to shore power.

I used 4 and 6 wire telephone cable to hook up the two new LED lights - very small wires. I connected to a light circuit with a 15 Amp fuse. This was uncomfortable; a short in the small wire part of the circuit could greatly exceed their current capacity and cause a fire. I put my meter in 10 Amp current mode in place of the fuse and found that the maximum current actually drawn was well under 5 Amps even on shore power, so I replaced that fuse with a 5 Amp one. Much better but I'll be looking for a 1 Amp inline fuse to make it right.


2004 Adventurer (Canadian) 20 footer - Alberta, Canada


2oldman

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Posted: 06/29/12 11:04pm Link  |  Print  |  Notify Moderator

Harvey51 wrote:

I was very surprised that the LED strips got very hot!
They're probably the cheap ones. They don't have voltage regulation and may burn out in a few months.

gbopp

The Keystone State

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Posted: 06/30/12 06:31am Link  |  Print  |  Notify Moderator

Good job! It's always nice to have a few extra reading lights.
Let us know if the resistor/diodes lower the operating temperature.

tenbear

Northern Vermont, USA

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Posted: 06/30/12 07:52am Link  |  Print  |  Notify Moderator

As an alternative to resistors you could use this voltage regulator to control the voltage to all your LEDs. I use one for my TV and it keeps the voltage pretty close to 12 volts.


Class C, 2004/5 Four Winds Dutchman Express 28A, Chevy chassis
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wa8yxm

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Posted: 06/30/12 08:56am Link  |  Print  |  Notify Moderator

I like the voltage regulator system.. If I were designing a LED bank for automotive use I would start with some kind of 3 terminal regulator, NOT the more complex one noted above but prehaps a 9 volt or 5 volt regulator.

Then I'd put 2 or 3 LED's in series and figure out the proper resistor
Then 2 or 3 more with another resistor

And so on

The regulator would keep them powered and by putting 2 or 3 in series I get to use the same current over and over (And over) again. (Plus the resistor does NOT get as hot).

NOTE that both the voltage regulator AND the series resistor will generate waste heat (Waste power) so the less you drop with these devices.. The better.


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tenbear

Northern Vermont, USA

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Posted: 06/30/12 10:34am Link  |  Print  |  Notify Moderator

wa8yxm wrote:

Snip...

NOTE that both the voltage regulator AND the series resistor will generate waste heat (Waste power) so the less you drop with these devices.. The better.


The OP states that the current for the LED increased from 150 mA to 290 mA. With the regulator in there the voltage would be limited to 12v so the current would stay at 150 mA. The wasted current used by the regulator would be less than the additional 140 mA that the LED would have used so there would probably be a net gain, more when many LEDs are on the same regulator, when the lights are on. When the lights are off the regulator would draw a small current. That current doesn't register on my clamp-on meter (0.1A resolution).

Note that I haven't tried this so it is just theory. I've been known to be wrong before.

Harvey51

Alberta

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Posted: 06/30/12 11:14am Link  |  Print  |  Notify Moderator

Quote:

As an alternative to resistors you could use this voltage regulator to control the voltage to all your LEDs. I use one for my TV and it keeps the voltage pretty close to 12 volts.

That is amazing! Three bucks including shipping and it magically controls the voltage. I was going to ask for instructions but I see in the picture it just has in, out and ground connectors.

Yes, I think the resistor (or regulator) would produce much less heat than the light for sure - now half the power goes to heat, with the resistor dropping 1 volt only about 1/12th of half of it. But the voltage might be too low when running on batteries; maybe tricky to get a good compromise resistance to work at both voltages. The regulator is a perfect solution.

Better still to pay an extra buck to get a light with built in regulator.
Do we know which ebay sellers have those?

2oldman

Biloxi

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Posted: 06/30/12 11:15am Link  |  Print  |  Notify Moderator

Harvey51 wrote:

Three bucks including shipping and it magically controls the voltage.
Great, as long as it doesn't overheat.

tenbear

Northern Vermont, USA

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Posted: 06/30/12 11:26am Link  |  Print  |  Notify Moderator

Harvey51 wrote:

Quote:

As an alternative to resistors you could use this voltage regulator to control the voltage to all your LEDs. I use one for my TV and it keeps the voltage pretty close to 12 volts.

That is amazing! Three bucks including shipping and it magically controls the voltage. I was going to ask for instructions but I see in the picture it just has in, out and ground connectors.

Yes, I think the resistor (or regulator) would produce much less heat than the light for sure - now half the power goes to heat, with the resistor dropping 1 volt only about 1/12th of half of it. But the voltage might be too low when running on batteries; maybe tricky to get a good compromise resistance to work at both voltages. The regulator is a perfect solution.

Better still to pay an extra buck to get a light with built in regulator.
Do we know which ebay sellers have those?


AFAIK none of the panels have a regulator. Be aware that the regulator is rated for 3A. You could put all of your LEDs on one regulator.

tenbear

Northern Vermont, USA

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Posted: 06/30/12 11:31am Link  |  Print  |  Notify Moderator

2oldman wrote:

Harvey51 wrote:

Three bucks including shipping and it magically controls the voltage.
Great, as long as it doesn't overheat.


As I said I use one on my TV. The TV draws about 1.4A. The regulator is housed in a small plastic box and gets barely warm after hours of operation. It would probably get warmer if it was reducing 50v to 12v.

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