Dimmer circuit

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Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=71803
Printed Date: May 13, 2025 at 8:36 AM

Topic: Dimmer circuit

Posted By: kacade
Subject: Dimmer circuit
Date Posted: January 30, 2006 at 1:38 AM

Hi, I'm a new member from UAE

I am doing a dimmer circuit for my son's project in school. I have 12 Vdc battery at 2.2 Ah and a 12V 50W halogen bulb. I cannot find a 12Vdc dimmer in our place. I found one 12V dimmer switch but when i ask the sales person if it works on a 12V battery supply, his answer was no. Is there a possibility to use that 220Vac or 12Vac dimmer switch with my stuff, 12Vdc, 2.2Ah battery and 12V 50W halogen bulb?

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rldestura

Replies:

Posted By: ff-mike
Date Posted: January 30, 2006 at 11:23 AM

An AC dimmer will not work, as AC dimmers basically are used to 'chop' some of the AC waveform to reduce how long the lamp is lit.
Look into these topics:
dimmer switch problems
Resistor for daytime running lights

Posted By: kacade
Date Posted: January 30, 2006 at 10:27 PM

I am trying to install, instead of using a dimmer switch, 4 way switches with resistors in each terminals. Does putting resistor in each terminal dims the light of the bulb?

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rldestura

Posted By: ff-mike
Date Posted: February 01, 2006 at 3:01 PM

Best thing to do is to use diodes to drop the voltage, the following is based on using silicon diodes which typically drop 0.7 volts. You would want diodes rated for 5 amps, or 2 3-amp diodes in parallel would work. Data Table follows

Diodes Volts Lumens Brightness
- 0     12.00   100%     100%
- 1     11.30    82%      66%
- 2     10.60    66%      43%
- 3      9.90    52%      27%
- 4      9.20    41%      16%

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