Automatic Headlight Brightness Switch


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Driving the highway with your high-beam headlights can really increase your visibility, but can be a blinding hazard for other drivers. This simple circuit can be wired into your headlight switch to provide automatic switching between high and low beam headlights when there is oncoming traffic. It does this by sensing the lights of that traffic. In this way, you can drive safely with your high-beams on without blinding other drivers.

Schematic


Schematic for Automatic Headlight Brightness Switch

Parts

Part
Total Qty.
Description
Substitutions
R115K 1/4W Resistor
R2, R3, R435K Pot
Q11NPN Phototransistor
Q212N3906 PNP Transistor
K11Low Current 12V SPST Relay
K21High Current 12V SPDT Relay
S11SPST Switch
B11Car Battery
MISC1Case, wire, board, knobs for pots

Notes

  1. Q1 should me mounted in such a way so it points toward the front of the car with a clear line of site. Suitable places are on the dashboard, in the front grill, etc.
  2. Adjust all the pots for proper response by testing on a deserted road.
  3. S1 enables and disables the circuit.
  4. B1 is, obviously, in the car already.
  5. Before you try to connect this circuit, get a wiring diagram for your car. Some auto manufacturers do weird things with wiring.
  6. Connection A goes to the high beam circuit, B goes to the headlight switch common and C connects to the low beam circuit.

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Comments

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shiva
Automatic Headlight Brightness Switch
Wednesday, September 17, 2014 9:49:10 AM
Good concept ...I want this one as my project please help me to implement this one and please give information about this like block diagram,specification and all
venki
Automatic Headlight Brightness Switch
Thursday, October 24, 2013 1:20:33 PM
Where do A, B & C connect, how are they attached to the circuit and where in the car exactly is the circuit connected? Please send me the reply on my email address. Please also send me the details of how the circuit works its analysis. I would like to use for my project because it is so nice.
reza
Automatic Headlight Brightness Switch
Tuesday, April 09, 2013 3:03:18 AM
Where do A, B & C connect, how are they attached to the circuit and where in the car exactly is the circuit connected? Please send me the reply on my emial address. Please also send me the details of how the cicuit works its analysis. I would like to use for my project becuase it is so good!!!!!!!!1
anonymous
Automatic Headlight Brightness Switch
Monday, July 09, 2012 6:48:10 PM
Do the work yourself, Lukas
Lukas
Hi!! I'm a student and this circuit is my hole project!!! Oh yes!!! Can you please, if that is possible, the analysis of it, the diagram, the function etc. Please!!! That would be very helpful for me 'cause I cannot find anything else elsewhere :/
Wednesday, May 30, 2012 10:23:26 PM
Hi!! I'm a student and this circuit is my hole project!!! Oh yes!!! Can you please, if that is possible, the analysis of it, the diagram, the function etc. Please!!! That would be very helpful for me 'cause I cannot find anything else elsewhere :/
sarun
Automatic Headlight Brightness Switch
Sunday, August 07, 2011 6:24:05 AM
Where do A, B & C connect, how are they attached to the circuit and where in the car exactly is the circuit connected? Please send me the reply on my emial address. Please also send me the details of how the cicuit works its analysis. I would like to use for my project becuase it is so good!!!!!!!!1
ndayisenga jean claude
Automatic Headlight Brightness Switch
Sunday, January 23, 2011 3:22:18 PM
hey man this circuit is so great .i wanna know how and where we connect this in the car ,if is possible show me a picture of car connected with this circuit thinks i like them!!!!!!!!!!!!
Weedo
Automatic Headlight Brightness Switch
Sunday, September 19, 2010 7:20:20 AM
photodiode would make a better in this circuit, cheaper, and easier. Stijn... yeah sure you switch them off +- 400 but did ya know that you can see the oncoming cars high beam like 600+m, photo diode senses this beam (if propelly mounted) like 1-2,5Km from u.
Cesar
Automatic Headlight Brightness Switch
Thursday, June 03, 2010 10:40:35 AM
Adjusting the pots R3 and R4 to the minimun will create a short to the battery terminals, did you notice that? How can be this problem fixed? Thanks
Timothy
Automatic Headlight Brightness Switch
Friday, February 19, 2010 1:10:54 PM
Where do A, B & C connect, how are they attached to the circuit and where in the car exactly is the circuit connected? Please send me the reply on my emial address. Please also send me the details of how the cicuit works its analysis. I would like to use for my project becuase it is so good. Thanks a banch. God Bless You
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