Using single filament bulb as a dual filament bulb.

Thread Starter

ej0408

Joined Oct 15, 2017
2
Hello all,

First post on here, used the forum a few times to solve a couple issues. Just thought I would share my experience with using a simple way to use a single filament bulb the same as a dual filament bulb. This was used for a set (2) single filament bulbs on the front of a vehicle, not the tail lights. I used one 15 Ohm resistor in my setup with 2 led bulbs. This may change to match your original dual filament bulb brightness. Any diode that prevents 12V from back feeding into the original circuit will work I believe.Single filament to act as Dual filament.png
 

Alec_t

Joined Sep 17, 2013
11,878
Welcome to AAC!
Dual-filament bulbs have the main and dip beams aimed in slightly different directions. Don't you need that function for compliance with vehicle/traffic regulations?
 

ian field

Joined Oct 27, 2012
6,539
Welcome to AAC!
Dual-filament bulbs have the main and dip beams aimed in slightly different directions. Don't you need that function for compliance with vehicle/traffic regulations?
Past Yamaha motorcycle headlamp bulbs didn't have any metal shade behind the dip filament. Obviously both filaments couldn't occupy the same space, so one was slightly offset and produced an offset beam angle. It didn't have the same sharp defined dip beam, and I always wondered how they got away with it.
 

ian field

Joined Oct 27, 2012
6,539
Only if the current source is controlled by a PIC and the clock for the PIC is a 555.

ak
Atom bomb to kill an ant hill.

I vaguely remember a programmable current source in TO92 (sort of a counterpart to the TL431). A current multiplier and switch in a second current setting resistor.
 
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