Dimmer for a 12V 50W halogen - Electronic Circuits Projects Diagrams Free

florida · 27th October 2009, 01:16 AM

I’m looking for a schematic or tutorial for a dimmer capable of controlling a 12V 50W DC halogen spotlight. Commercial dimmers are expensive specialty items that won’t work for my application. There is no commercial dimmer that is saltwater proof. The dimmer will control a 2 mil CP spotlight and will be used for marine navigation. Lately I’ve been using a rheostat from an old truck heater; it generates way to much heat.

Thanks for the help.

Sceadwian · 27th October 2009, 01:47 AM

A simple 12 volt 5 amp PWM circuit encapsulated in hot glue or epoxy would work fine. However if I'm not mistaken halogen bulbs don't like being dimmed.

florida · 27th October 2009, 02:14 AM

Thanks, great idea

Dimming lowers the temperature causing carbon to build up on the filament. Running it full blast for one minute for each hour of dimming is supposed to alleviate that.

florida · 27th October 2009, 11:17 PM

Would this PWM circuit in the video tutorial work? Probably not it only handles 1 amp correct?

YouTube - PWM Tutorial

florida · 2nd November 2009, 01:10 AM

Sorry to bump this thread but when it was approved by mod. it didn’t show up on new post. It was buried on page 5 of the Electronic project forum. See above post.

Thanks

kchriste · 2nd November 2009, 02:52 AM

If you changed R2 to 100Ω and replaced T1 with a suitable FET, it'll work OK. Or you could replace R2 with a 100Ω 2watt and replace T1 with a better transistor. I prefer using the FET myself, if for nothing else, than reducing the power dissipation in R2.

bountyhunter · 2nd November 2009, 07:41 PM

You could use a free running 555 timer with adjustable duty cycle driving a P-FET (high side drive) to the lamp to dim it. I would set the osc frequency to maybe 500 Hz ballpark. If the on resistance of the P-FET is low, the FET wll not need a heatsink. Here is an example circuit, you would want to make the 4.7uF cap smaller to get faster oscillation frequency. This one is designed to make a headlight flash as a warning light. The 30k/100k resistors can be varied to change duty cycle.

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27th October 2009, 01:16 AM	#1
florida	Dimmer for a 12V 50W halogen I’m looking for a schematic or tutorial for a dimmer capable of controlling a 12V 50W DC halogen spotlight. Commercial dimmers are expensive specialty items that won’t work for my application. There is no commercial dimmer that is saltwater proof. The dimmer will control a 2 mil CP spotlight and will be used for marine navigation. Lately I’ve been using a rheostat from an old truck heater; it generates way to much heat. Thanks for the help.

27th October 2009, 01:47 AM	#2
Sceadwian	A simple 12 volt 5 amp PWM circuit encapsulated in hot glue or epoxy would work fine. However if I'm not mistaken halogen bulbs don't like being dimmed. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

27th October 2009, 02:14 AM	#3
florida	Thanks, great idea Dimming lowers the temperature causing carbon to build up on the filament. Running it full blast for one minute for each hour of dimming is supposed to alleviate that.

27th October 2009, 11:17 PM	#4
florida	Would this PWM circuit in the video tutorial work? Probably not it only handles 1 amp correct? YouTube - PWM Tutorial

2nd November 2009, 01:10 AM	#5
florida	Sorry to bump this thread but when it was approved by mod. it didn’t show up on new post. It was buried on page 5 of the Electronic project forum. See above post. Thanks

2nd November 2009, 02:52 AM	#6
kchriste	If you changed R2 to 100Ω and replaced T1 with a suitable FET, it'll work OK. Or you could replace R2 with a 100Ω 2watt and replace T1 with a better transistor. I prefer using the FET myself, if for nothing else, than reducing the power dissipation in R2. __________________ Inside every little problem, is a big problem trying to get out. Last edited by kchriste; 2nd November 2009 at 02:53 AM.

2nd November 2009, 07:41 PM	#7
bountyhunter	You could use a free running 555 timer with adjustable duty cycle driving a P-FET (high side drive) to the lamp to dim it. I would set the osc frequency to maybe 500 Hz ballpark. If the on resistance of the P-FET is low, the FET wll not need a heatsink. Here is an example circuit, you would want to make the 4.7uF cap smaller to get faster oscillation frequency. This one is designed to make a headlight flash as a warning light. The 30k/100k resistors can be varied to change duty cycle. Attached Thumbnails Last edited by bountyhunter; 2nd November 2009 at 07:58 PM.