Led driver circuit for automobile tail/brake light

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SgtWookie

Joined Jul 17, 2007
22,201
why we require flasher ? because at indicator bulb point i am getting flasher output, inside indicator housing if we put constant current circuit with LED would be enough.
Your flasher is designed to operate with a certain amount of current flowing through it; this current also flows through the turn signal lamps.

The current heats up a bi-metal strip inside the flasher, which when heated enough, disconnects the current from the lamps. As the bi-metal strip cools, the current to the lamps is again connected. The cycle then repeats at a 1Hz-3Hz rate.

The current through even several LED strings is so much less than that of a pair of turn signal lamps, there would not be enough current to heat the bi-metal strip in the flasher, so your turn signal LEDs would not flash; they would stay on until you turned off the switch.

Try removing one of your turn signal bulbs, and you will notice that the other remaining bulb either does not flash at all, or flashes very slowly.
As for as head lamp is concerned it serves as standby (i will retain standard head lamp),
it would be helpful if give me constant current circuit along with formula to calculate resistors value with respect to LED's ratings
I obtained the values for the resistance, etc. for the last circuit by modeling it in a PSPICE simulation.

The transistors which were used in the last circuit have a practical current limit of about 100mA. I do not know what you are planning on using for the "auxiliary headlamp" LED, but anything remotely approaching "useful" light output would require at least several amperes of current. You would need a much more sophisticated (and complex) circuit. It would not be a beginner's level project.
 
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Audioguru

Joined Dec 20, 2007
11,251
Most of us are not in India so we don't know what parts you can buy.
We use millions of parts that you can't get.
Maybe you should go on a forum in India.
 
Hi i'm Mario from Italy,this site is fantastic...how can i modify leds current??
I have to change the two resistor near the Shottkys?
Thank you!
 
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SgtWookie

Joined Jul 17, 2007
22,201
...how can i modify leds current??
I have to change the two resistor near the Shottkys?
Yes.

The 91 Ohm resistor gives 8.16mA@10.4v to 8.4mA@14.5v through the LEDs when just S1 is closed.

With both S1 and S2 closed, current is 28.6mA@10.4v to 30mA@14.5v.

With just S2 closed, current is 27.5mA@10.4v to 28.2mA@14.5v.
 

DMC_rider

Joined Oct 21, 2008
4
hello all. I am Shoeb from Bangladesh and i am planning to replace all the bulbs (except headlamps) in my JDM 95 Corolla with LEDs. in the dash, turn indicators, tail lamps, brakes- all of them. i found a circuit for the tail lamps- thanks to SgtWookie... now if only i could get help on the other sections...

there's a question though- SgtWookie's circuit drives 3 LEDs. can i use it to drive an array of 6, 9, or 12 LEDs? if not, what needs to be changed?

and just to give you an idea- people just dont care about traffic laws here. so you dont need to worry about brightness or angle of visibility for the LEDs. but rest assured, when my project is done, visibility will not be a problem.

and i will have to use those narrow-beam low-power LEDs like those found in cheap LED flashlights, because that's all we have back here.
 

SgtWookie

Joined Jul 17, 2007
22,201
hello all. I am Shoeb from Bangladesh and i am planning to replace all the bulbs (except headlamps) in my JDM 95 Corolla with LEDs. in the dash, turn indicators, tail lamps, brakes- all of them. i found a circuit for the tail lamps- thanks to SgtWookie... now if only i could get help on the other sections...

there's a question though- SgtWookie's circuit drives 3 LEDs. can i use it to drive an array of 6, 9, or 12 LEDs?
No. It is a constant current circuit, for two distinctly different current levels.
if not, what needs to be changed?
Use a voltage regulator across the array, and current limiting resistors for each string in the array. Since I have absolutely no clue what voltage regulators are available there, you will have to tell us.
and i will have to use those narrow-beam low-power LEDs like those found in cheap LED flashlights, because that's all we have back here.
Those are not suitable for automotive use.

You should continue using the standard incandescent lamps.
 

DMC_rider

Joined Oct 21, 2008
4
thanks for all the info.

but why cant i use those LEDs? because of their electrical or optical characteristics? if electrical characteristic is the issue, then isn't that the reason why we are using all these circuitry? well you will have to bear with me... my knowledge about these things is rudimentary... and i can take care of the optical issues, don't worry about that.

actually what I'm doing here is basic research. so if you could just tell me what voltage regulator and resistor combination you would use, i will get back to you on updated info.

and thanks a big huge lot again... you are really helpful.
 
Hi im allen from Philippines, does anyone here uses CRD rather than resistors in making LED taillights? could someone tell which is better between them. thank you guys!
 

Wendy

Joined Mar 24, 2008
21,848
What is a CRD?

You really need to start your own thread. This one was done, and AAC has a policy about hijacking threads (using other people threads for your own project).
 

thedt

Joined Dec 12, 2008
15
Was looking at these for tail lights

http://cgi.ebay.com/20-5W-8mm-Red-StrawHat-140-40000-mcd-LED-USA_W0QQitemZ230317506941QQihZ013QQcategoryZ66954QQcmdZViewItemQQ_trksidZp1742.m153.l1262

Brightness - 40,000-60,000 mcd
Forward Current - 100mA max
Forward Voltage - 2.0 typ, 2.4 max
Reverse Voltage - 5v
View Angle - 140 Degrees


or should i stick with the
HPWT-DH00-G4000?
VOLTAGE: 2.6V TYPICAL FOWARD VOLTAGE
CURRENT: 70mA MAX
POWER: 221mW MAX
OUTPUT: 5 LUMENS TYPICAL
REVERSE VOLTAGE: 10V
VIEWING ANGLE: 50 DEGREES​
 
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