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Old 02-12-2005, 12:07 PM   #1
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LED Dimmer

Two questions for the DC gurus.

1) Can I mix LED and Standard Bulbs on a circuit. If they are on a flasher circuit must an addition LED flasher be on the LED branch which would be after the TV flasher?

2) Can LED's be used with a standard DC low amp dimmer (5 amps) without some additional resistance.

3) When Dimming standard DC bulbs do you use less amphours. ie. save power?

OK so I don't count two good.
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Old 02-12-2005, 12:24 PM   #2
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1. Yes, you can use LED bulb replacements and incandescent bulbs in parallel on the same circuit, without a special flasher. You can flash them on and off with the incandescents. The only problem you might run into is replacing most or all of the incandescents with LEDs which may not draw enough current to heat up the element in the flasher. In that case, you use an equalizer in parallel with the LED lights. It's just a resistor that increases the current draw through the flasher.

2. No, you cannot use most LED bulb replacements with a standard dimmer, at least the way the dimmer is intended to be used. Quality LED lamps have a current regulating integrated circuit feeding typically three white LEDs in series. If the voltage feeding them reduces current too much the IC quits functioning and they quit conducting. Cheap LED lamps have just a dropping resistor in series with one or more LEDs. The more LEDs in series (meaning the smaller the dropping resistor), the quicker they dim with a voltage drop. They dim much quicker than incandescents with a lot less voltage drop, in other words from bright to off in only part of the dimmer's range. You can build your own dimmable LED fixture with a variable resistor controlling the the IC.

3. Yes, you can save power with a dimmer, however with cheap ones that just increase resistance, the light level goes down faster than the current and power is wasted as heat across the resistance. Good DC dimmers will use electronics to maintain full voltage but turn the bulb on and off faster than the eye can see to reduce the average power.
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Old 02-12-2005, 02:50 PM   #3
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Quote:
Originally Posted by RoadKingMoe
Good DC dimmers will use electronics to maintain full voltage but turn the bulb on and off faster than the eye can see to reduce the average power.
On and Off like FLASHING? Do they tell you the rate in the specs? Has to be 30 plus I would think.

Glad I asked. So I can add some LED running lights on the sides of the AS at the bottom.

If I change the Stop lights to LED do I add an LED Flasher to the circuit? I may have to do this on the bench just to see what happens with the truck lights flashing. Two flashers at difference rates could make some interesting light.
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Old 02-12-2005, 03:18 PM   #4
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The rate is much higher than 30 fps, but I can't recall exactly.

If you are going to use 1157 replacement LED bulbs, make sure the sockets in the taillights point straight back so the rounded ends of the LEDs will be pointing straight back. You might try one and then view it from 45 degrees off to either side. You might not like what you see.

No, you do not need an LED flasher.
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Old 02-13-2005, 07:57 AM   #5
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I put some white LED bulbs in my reading lights at the front of the coach. They make a nice reading light, but that is about it. They are VERY directional, and don't work worth a hoot in the ceiling fixtures, in which the bulbs are horizontal.
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