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12 Volt Car Actuator Circuit

Discussion in 'Sensors and Actuators' started by yoshiko, Feb 27, 2015.

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  1. yoshiko


    Feb 27, 2015
    Need Help with a 12 volt car actuator circuit. I will use my car alarm to open the trunk but I need to install the actuator and the circuit. The car alarm has a wire that will accept up to -500mA of current when I push a button on my keys. That will be the trigger to trigger the circuit I need to design that will operate the actuator. I have a fairly good knowledge of electronics and various ICs but I tend to stay away from micro-controllers because I still need to learn the programing language.

    Any Ideas will be much appreciated.
  2. Kiwi


    Jan 28, 2013
    Is the actuator just a solenoid that trips the lock? If it is use the alarm to operate an automotive style 12v mini relay that has a diode or resistor protected coil.
    Gryd3 likes this.
  3. yoshiko


    Feb 27, 2015
    Yes - You're right. but I need a circuit to operate it. The alarm will sink a pulse of -1mA to trigger a 2 pulse square wave.
    I have a schematic but this website won't let me upload a jpg of the circuit.
    I also build a prototype using a breadboard and the circuit works perfectly except when I replace the dummy load with the actuator, the circuit causes the actuator to oscillates so fast that the actuator don't know which direction to go. Actually the 555 timer causes the relay to turn on and off very rapidly. It should only oscillate one cycle and then stop.

    2 x Timer 555 IC were connected to operate in sequences. My alarm will trigger one 555 timer which will trigger a transistor which will operate a 12 v mini relay that uses 30mA. The relay will send current to the actuator. When this is complete, the 2nd 555 timer will then operate the same exact sequence, except that now the current will reverse its direction in the actuator.
  4. Hunter


    Oct 18, 2012
    I may be of some help, but first I need some information. brand and model of alarm, is the actuator for opening the latch or to raise the trunk after unlatching? is it a linear actuator and simple door lock actuator
  5. davenn

    davenn Moderator

    Sep 5, 2009
    uploading jpg's is no problem ... I upload lots of them

    make the file a max of 800x600 pixels and 100kb or less
  6. yoshiko


    Feb 27, 2015
    At this resolution you can't even see the resistor values on my schematic. And I'm still getting an error when I try to upload a jpg
  7. yoshiko


    Feb 27, 2015
    Thanks Hunter, The actuator is a simple door lock that move in and out by 0.5 inch and uses 1.6A at 12 volts. But the Back EMF from the actuator are interfering with the 555 timer operations because they both use a common ground. However the 555 are powered by a 7 volt variable lm317 regulator.
  8. mursal


    Dec 13, 2013
    As you know the 555's will not drive a 1.6A load so you will need at least a relay on the output. Place a freewheeling diode across the coil of the relay so it will not conduct in normal operation, this should reduce back EMF from the relay coil.
    Hope this helps .......
  9. yoshiko


    Feb 27, 2015
    Thanks mursal. The 555 drives a transistor which drive a 12 volt mini relay which drives the 1.6A actuator.
    Back emf from the relay coil is not a problem. the problem lies with the back emf from the actuator. However I've added a snubber across the actuator but that still doesn't help.
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