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Old 07-23-2015, 02:44 AM   #1
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Default How can I underdrive my 50W fog bulbs so they last forever as my Canadian DRL lights.

How can I underdrive my 50W fog bulbs so they last forever as my Canadian DRL lights. They would still be quite visible at 40watts I would guess and taking the volts down by XX percent should add a few thousand or more hours of life. Resistors ?? But which ones would I want ? I don't know.

I haven't tested the actual voltage to the bulbs yet.

I know that LED's last forever but I just spent a whopping $15 on a pair of Hella Yellow bulbs to go in my yellow laminated fogs so I want to explore the incandescents.
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Old 07-23-2015, 10:01 AM   #2
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Resistors = probably not. Well, you could get 10W resistors, but certainly not the best way.

Look into the ebay voltage step down modules similar to this:

131558369217 but higher power
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Old 07-23-2015, 01:41 PM   #3
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<p>&nbsp;</p><p>I understand that running halogens at low voltage disturbs the redeposition cycle, and may not lead to increased life. https://en.wikipedia.org/wiki/Halogen_lamp</p><p>&nbsp;</p>
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Old 07-23-2015, 01:44 PM   #4
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DC Step Down Adjustable Power Supply

I'll look into these thanks
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Old 07-23-2015, 01:53 PM   #5
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Originally Posted by DNMakinson View Post
<p>&nbsp;</p><p>I understand that running halogens at low voltage disturbs the redeposition cycle, and may not lead to increased life. https://en.wikipedia.org/wiki/Halogen_lamp</p><p>&nbsp;</p>

I'm hoping to only underdrive them a little bit. For example if they are getting say 13.5V at the lights I'd like to take it down to 13 or 12.5V.

I should measure my headlights V as that is what the Canadian cars use as DRL's - a lower voltage is sent to the headlights so that they last much, much longer.
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Old 07-23-2015, 03:46 PM   #6
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If you wanted to loose only 0.5-1.0 volts, smaller diameter wiring/worst ground will get you there. Essentially using wire as a resistor.

Or possibly look into using a DRL module from another car directly? Might be the easy button.
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Old 07-24-2015, 01:23 PM   #7
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Default How can I underdrive my 50W fog bulbs so they last forever as my Canadian DRL lights.

How do halogens respond to PWM?
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Old 07-24-2015, 02:59 PM   #8
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<p>
Quote:
Originally Posted by patsmx5 View Post
If you wanted to loose only 0.5-1.0 volts, smaller diameter wiring/worst ground will get you there. Essentially using wire as a resistor. Or possibly look into using a DRL module from another car directly? Might be the easy button.
</p><p>That won't change the desired current draw from the lights.The wires just won't be able to handle it and might melt/break.</p>
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Old 07-24-2015, 03:09 PM   #9
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Quote:
Originally Posted by NiklasFalk View Post
How do halogens respond to PWM?
You know the dimmable halogen floor lamps which occasionally set curtains on fire? The dimmers in those use a form of PWM (phase angle control) to chop the AC waveform using a Triac or a pair of SCRs.
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Old 07-25-2015, 12:56 AM   #10
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The thermal relaxation of the filiment is going to be way too slow to care about a chopper or pwm.
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Old 07-25-2015, 11:52 AM   #11
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Much more technical than in was expecting.
I thought I could thrown in a few resistors like my ATV heated grips run when in the low setting and call it a day. - Ceramic Resistor
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Old 07-25-2015, 12:36 PM   #12
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Yep, something along those lines would work. If you go that route, be sure to mount the resistors to a suitable heat sink.
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Old 07-25-2015, 01:09 PM   #13
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Quote:
Originally Posted by Landrew View Post
Much more technical than in was expecting.
I thought I could thrown in a few resistors like my ATV heated grips run when in the low setting and call it a day. - Ceramic Resistor
You can, but as Ted noted, they will generate quite a lot of heat, so mount them appropriately.

Assuming a lamp is rated for 50 watts at 14 volts, it's got a resistance of 3.92 ohms. If you put a 1 ohm resistor in series with it, total system wattage will drop to 40 watts, of which the resistor will be dissipating about 8 watts and the lamp will be dissipating about 32.

Last edited by Joe Perez; 07-26-2015 at 12:10 AM.
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Old 07-25-2015, 11:39 PM   #14
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You know, 100W 10ohm resistors are like 6 bucks on amazon prime. Sounds pretty easy to me.
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Old 07-29-2015, 04:44 AM   #15
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Quote:
Originally Posted by Joe Perez View Post
You can, but as Ted noted, they will generate quite a lot of heat, so mount them appropriately.

Assuming a lamp is rated for 50 watts at 14 volts, it's got a resistance of 3.92 ohms. If you put a 1 ohm resistor in series with it, total system wattage will drop to 40 watts, of which the resistor will be dissipating about 8 watts and the lamp will be dissipating about 32.


Sweet, I will try this.

They will be mounted around the front fender and get some airflow.
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Old 07-29-2015, 11:04 AM   #16
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Conduction >> convection
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Old 07-29-2015, 12:21 PM   #17
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Default How can I underdrive my 50W fog bulbs so they last forever as my Canadian DRL lights.

The simplest way would be to couple them in series, but 7V might be too low.
Requires very little in parts.
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Old 07-30-2015, 03:21 AM   #18
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ebayed some gold aluminum housed 1 ohm 100 watt resistors. It'll take 2 weeks to get here. I'll be playing with the DRL and side markers until they show up.
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Old 07-31-2015, 09:45 AM   #19
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Quote:
Originally Posted by NiklasFalk View Post
The simplest way would be to couple them in series, but 7V might be too low.
Requires very little in parts.
I did this with a relay one time, wired so that I could switch from series to parallel.
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Old 08-11-2015, 05:38 PM   #20
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FYI on a Canadian made car the DRL modules black with white wire is the one that activates the headlight DRL's. remove it and its manual only.

With that out of the way and the resistors having shown up I proceeded to install my Hella yellows into the fogs.

Resistored light on the passenger side regular in drivers. Yes that resistor gets hot, we will see how it survives down there. Trying it this way and see how things go for a few months.





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