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
Stijn
Automatic Headlight Brightness Switch
Thursday, January 21, 2010 3:25:06 PM
Does this really work? I do not believe it will. Usually I switch my high-beam headlight off when I see someone coming from +- 400 meters. This tiny phototransistor will never detect the oncoming headlights over the street lanterns.
evi
Automatic Headlight Brightness Switch
Wednesday, December 23, 2009 5:45:51 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 :/
mpouxesas
Automatic Headlight Brightness Switch
Sunday, November 29, 2009 11:20:41 AM
hi man,this is really a great job..bravo i want to design it on a PCB where i can find it??thx
garv
Automatic Headlight Brightness Switch
Tuesday, July 07, 2009 8:07:29 AM
Can we use this ckt to bike ?
Gaurav
Automatic Headlight Brightness Switch
Saturday, April 11, 2009 8:30:49 AM
hi frnd! this is really a great job............... but i have few problems as i want to design it on a PCB. so if possible can u get me the PCB layout of this circuit. also a explanatory description of this whole circuit. also how it works and where it should be attached in the vehichle........ i will be very thankful to u............
RAJ
Automatic Headlight Brightness Switch
Thursday, January 15, 2009 7:35:32 AM
Hey man this circuit is jus great. Particularly in India such circuits need to be implemented in the vehicles at the time of manufacturing itself because many of the people don't even understand the risk of driving with high-beam even when not neccesary. Good work man.
anonymous
Automatic Headlight Brightness Switch
Friday, December 12, 2008 11:39:02 AM
Why did omit the back emf diode from the relay coil?
garv
Automatic Headlight Brightness Switch
Wednesday, September 17, 2008 9:22:59 AM
hi bro good 1 i'm facing big problem while driving at night as u know the problem with HeroHonda CBZ* it's headlight power is very low I din't get what is k1& kt please sent me this circuit in detail thanks garv
mani
Automatic Headlight Brightness Switch
Saturday, August 16, 2008 4:23:04 PM
this circuit is of great use to the persons who drive but even don't know about flash on road as it is imp. tool of driver to drive properlly and to persons do not know about high and low beam usage which is great cause ofaccident in night
Steve
Automatic Headlight Brightness Switch
Thursday, January 24, 2008 5:05:27 AM
Guten tag.I am germany student, I like your circuit yes, if you email please me information how it work. i do this for school and i like cars, sexytime please danke kiss kiss
dhanu
Automatic Headlight Brightness Switch
Wednesday, January 23, 2008 9:35:23 AM
i really like this project ... could i know about the detail descriptions of the circuit and the cost of this project???????? thank uuuuuu...
Zeberdy
Automatic Headlight Brightness Switch
Thursday, January 17, 2008 9:26:16 AM
Yooo dis is well elpful i is gunna use it az me projec if youse can gis some more info like i wud much appreciate it aite. much loves. keep it reals Zebby xxooxx
jon dom
Automatic Headlight Brightness Switch
Thursday, January 10, 2008 8:56:25 AM
aaaaaaaaaaaaaye mate! kin waaaaaaaa this project is mint like it'd be reeet sound if ya could let me knows about some more info like i iz doing it for me project its sound! cannie wait kid hit me back inabit mert(Y)
jain
Automatic Headlight Brightness Switch
Thursday, January 10, 2008 5:29:13 AM
can u tell the minimum budget for this project
INGOSI
Automatic Headlight Brightness Switch
Sunday, December 16, 2007 6:21:35 AM
tell me more about the phototransistor (The specifications/characteristics) via my E mail
loet
Automatic Headlight Brightness Switch
Wednesday, December 12, 2007 12:43:06 PM
i really loved the design, its ballistic i would like work on it as my project but i'm having trouble with th 2 relays, can i replace the whole relay unit with one? also what if i want to use the darlington pair, may u advise me about how i would change the circuit. thanx
uday
Automatic Headlight Brightness Switch
Thursday, November 29, 2007 2:37:22 AM
where can i get the equipments for this project and what is the overall cost of the project
carlos
Automatic Headlight Brightness Switch
Friday, November 16, 2007 11:45:10 PM
where can i buy all the parts for this projects?

(Editor's notes: Electronics store.)

wubantos
Automatic Headlight Brightness Switch
Thursday, November 15, 2007 11:57:31 AM
i really like the circuit so if don't mind i really want to use it for my project so send me more detailt via my mail. thanks a lot
albano
Automatic Headlight Brightness Switch
Saturday, November 03, 2007 7:05:25 AM
where can i put output of the Low Current 12V SPST Relay and High Current 12V SPDT Relay.
aNDY k
Automatic Headlight Brightness Switch
Monday, October 29, 2007 8:17:49 AM
I am a student looking into using this idea for my project. Please send me further notation please :)
mohamed okda
power supply
Wednesday, October 24, 2007 12:30:19 PM
I want the whol circuit of the power supply of the computar and its requirments to give the real volts . and thanks for you.
prabhakar
Automatic Headlight Brightness Switch
Friday, October 05, 2007 3:00:01 PM
a photodiode instead of phototransistor 3 pots can be replaced by a single 1meg pot
jet
Automatic Headlight Brightness Switch
Thursday, October 04, 2007 4:14:39 AM
This design is interesting. Can i have more information about the flow of the diagram? We want this to be our project. Thanks lots.
anonymous
Automatic Headlight Brightness Switch
Friday, September 21, 2007 7:26:50 AM
can i remove the K1 SPST Relay?
arnol
Automatic Headlight Brightness Switch
Wednesday, September 12, 2007 8:29:54 AM
where is the LDR in the circuit
julian
Automatic Headlight Brightness Switch
Tuesday, September 11, 2007 4:35:42 AM
i have another design of the project i use op-amp coupled with transistor to activate the relay and it's working alright.......
krichi
Automatic Headlight Brightness Switch
Friday, September 07, 2007 11:00:37 AM
hi..congrats 4 bringin out such a good circuit..but if u cud plz .. furnish more details abt the circuit...thanx!
alezxy
Automatic Headlight Brightness Switch
Sunday, September 02, 2007 12:26:04 PM
can send the all the circuitry and notes?thx.i want to try this circuit
bala
Automatic Headlight Brightness Switch
Sunday, September 02, 2007 3:32:26 AM
The circuit is really excellent.... i want to make this as a project.... so plz send me the thorough working concept of this design...... thank you
natrajprabu
Automatic Headlight Brightness Switch-wish to know more.
Wednesday, August 22, 2007 11:17:54 AM
this is an jnnovative concept.i like to implement this practically.please help me in this circuit. i am just a beginner in hardware area.wish to hear from u soon.
hafis
Automatic Headlight Brightness Switch
Sunday, August 05, 2007 9:44:27 AM
This circute is very usefull for night driving....
abdulazeez
Automatic Headlight Brightness Switch
Thursday, July 26, 2007 1:08:06 PM
its a great circuit and its really cool very effective during foggy conditions,brillant work.
R.RanjithKumar
Automatic Headlight Brightness Switch
Tuesday, July 17, 2007 4:03:25 AM
Realy super concept which will reduce the accidents in the Transport
S.A.Srikanth
Automatic Headlight Brightness Switch
Monday, July 09, 2007 10:33:29 AM
i like this project...but kindly help me in circuit connection as soon as you can....
Raymond
Automatic Headlight Brightness Switch
Friday, June 15, 2007 2:03:11 PM
I am a technician and very happy to see such a simple but wonderful system. More grease to your elbow. Kindly furnish me with more information in relation to the circuitary connection. Thank you
Andrew Lutton
Automatic Headlight Brightness Switch
Friday, June 15, 2007 6:35:25 AM
I liked it very much and is very useful for everyday life.:)
george
Automatic Headlight Brightness Switch
Monday, June 11, 2007 10:24:26 PM
this is wounderfull, thanks for your effort to redues accident. am a student writting on your system. i well be gratefull if you would please send me source for furter information on the diagram and its operation. THANK YOU. PLEASE HELP ME.
karan
Automatic Headlight Brightness Switch
Tuesday, June 05, 2007 6:15:37 AM
it will be wonderful if we could get this information.
anonymous
Automatic Headlight Brightness Switch
Monday, May 21, 2007 9:53:12 AM
Could please send me information on how to adjust the circuit for the first test? I am having trouble getting the relays to switch over. All of the notes and circuitry would be beneficial.
crums
Automatic Headlight Brightness Switch
Saturday, May 12, 2007 3:37:22 AM
send that to me also with notes and all curcuitry
kibet ronoh david
audio ampolifier circuit
Thursday, May 10, 2007 4:29:47 AM
send that to me also with notes and all circuitry
kibet ronoh david
Automatic Headlight Brightness Switch
Thursday, May 10, 2007 4:23:51 AM
just a real work guys.please send me more notes on it.
george
Automatic Headlight Brightness Switch
Saturday, May 05, 2007 9:15:28 PM
wonderful ! fantastic! i am a student and need information about the above topic for my project work. thanks
anonymous
Automatic Headlight Brightness Switch
Thursday, April 26, 2007 1:47:21 AM
wonderful ! fantastic!
miguel_pork
Automatic Headlight Brightness Switch
Sunday, April 15, 2007 12:51:33 PM
solid state switches better than relay... less chance for blown head lamps... and LDR (light dependent resistor) is fast enough for this application. :)
anonymous AJ
Automatic Headlight Brightness Switch
Thursday, April 12, 2007 8:24:21 PM
These circuit can be used in race cars? Very interesting the circuit.
avinash
Automatic Headlight Brightness Switch
Sunday, April 01, 2007 1:17:53 AM
sir, here the sufficient explanation is notavailable for the circuit can you please send me the source for further explanation and block diagram for this circuit
erick
Automatic Headlight Brightness Switch
Saturday, March 10, 2007 10:35:31 AM
what is the high current relay max amp? 20A? Low current? 5A? please reply./... thanks!
Gagan
Automatic Headlight Brightness Switch
Thursday, March 01, 2007 12:12:15 PM
the circui was good but there is some drawback . What about the vhicles from the opposite side their headlights are not adjusted by the help of this circuit if they dont have the same circuit
mridul agnihotri
Automatic Headlight Brightness Switch
Thursday, March 01, 2007 1:59:27 AM
send me some more modified forms of this switch its a good idea
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