Need help on driving relay with PWM output

Discussion in 'The Projects Forum' started by StupidPig, Jul 28, 2009.

  1. StupidPig

    Thread Starter Member

    Jun 5, 2009
    12
    0
    Here is the background....
    My car using the Hi-beam as both Hi-beam and DRL, I would like to make the DRL function to a seperate LED circuit, So the Hi-beam bulb is only on when Hi-beam is switched on, and a set of LED will be on for DRL.

    I used a DMM to measure the voltage on the Hi-beam wires, and it gave me reading of about 12v when Hi-beam is on, and 7.6v when DRL on. So I was thought I can use a SPDT relay with 8v pull-in voltage to seperate the circuit for Hi-beam and DRL, then use another SPST relay with 6v pull-in voltage to switch on a 12v with the 7.6v output to drive the LED set.

    [​IMG]

    Looks good when Hi-beam is on, but the when DRL on, the LED is not turned on, and I hear some buzzing sound come from the relay. I guess the 7.6v for DRL may be actually achieved with PWM and thats why the relay didn't switch to on. So, is there any solution for this? Will adding a capacitor like the following works?

    [​IMG]
     
  2. StupidPig

    Thread Starter Member

    Jun 5, 2009
    12
    0
    Bump.... Nothing can be done? Or too simple for not worth for an answer?
     
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