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Need help smoothing out a PWM signal

Discussion in 'General Electronics Discussion' started by branndonw, May 28, 2013.

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  1. branndonw

    branndonw

    1
    0
    May 28, 2013
    Hey guys, Im pretty much a noob when it comes to electronics and need some help smoothing out a PWM signal. Im going to be modifying the headlamps circuit in my vehicle. The Body Control Module supplies a PWM ground to a solid state relay which then supplies voltage to the headlamps. When the vehicle is in Park, everything is off. When it is bright outside and the vehicle is placed into gear, Daytime Running Lamp mode is active and the headlamps run at 85% DC. When it gets dark, Headlamp mode is active and the headlamps run at 100% DC.

    What I want to do is to smooth that PWM ground so that I can use it to control a 12v mechanical relay in order to use my Park Lamps at 100% for DRL instead of the headlamps. If its necessary to use a solid state relay to convert that pwm ground to a pwm positive thats fine but I would prefer not to if at all possible to keep it as simple and inexpensive as possible.

    I've used a 100 ohm resistor and 100uf / 220uf / 470uf cap combos and successfully got the mechanical relay to switch and stay switched but the mechanical relay makes a faint humming sound that I am not comfortable with.

    Any help would be greatly appreciated. Thanks in advance.
     
    Last edited: May 28, 2013
  2. Lord_grezington

    Lord_grezington

    115
    2
    May 3, 2013
    We will need a schematic to see where you have put your resistor capacitors. The faint humming sound is due to the audible noise frequency (a resistor capacitor circuit can be set at a frequecy which is in the audible noise spectrum - usually from about 10khz to 20khz).

    Can you confirm that you want to use the DLR instead of the headlamps? If this is the case, we will need to know the power of the DLR and the headlamps. We should then be able to configure a circuit to either switch one to the other, or split them.

    Graham
     
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