Arduino Forum

Using Arduino => LEDs and Multiplexing => Topic started by: dutchronnie on Feb 15, 2012, 07:36 pm

Title: Led Lightning in Car
Post by: dutchronnie on Feb 15, 2012, 07:36 pm
I have a car with some led's for lightning.
I wat to change the leds into RGB leds, and control this led's with an arduino.
I have put out the existing led's and i have made a schematic of it, i will send the picture with this post.
It is an SMD led on a little PCB with 2 SMD resistors with the printing on it of 1002 = 10Kohm and 1301 = 1K3 ohm.

I don't understand the print.
one resistor is put over the positive and the negative?
Does somebody know how this works?
Title: Re: Led Lightning in Car
Post by: ArnieNFW on Feb 17, 2012, 11:08 am
It's weird, but this is usually done by led's which replace car-(exterior) lightning.
In some (recent?) cars there is electronics which determine if the light is still working. This can be done by measuring the current. When the light is changed from a normal bulb (halogene) to a led, the current is drasticly reduced. So the electronics thinks the bulb is broken and warns you should replace it. To let the electronic think the bulb is okay, a resistor is put in parallel to draw more current.
Long live the green planet (I = 13.8V/1300Ohm = 10mA; P=13.8*0.01=0.15Watt).
Title: Re: Led Lightning in Car
Post by: Chagrin on Feb 17, 2012, 03:15 pm
The resistor is used to emulate the higher resistance of an incandescent bulb. Specific to a turn signal, without the resistor the bulb would flash at an incorrect rate. Google for "turn signal hyperflash" for various explanations or look into how an automotive "flasher unit" works.
Title: Re: Led Lightning in Car
Post by: dutchronnie on Feb 18, 2012, 07:54 pm
Thanks for your explanations  :)