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    selenoid controlled by PWM

    Hi

    I need control four solenoid valves by PWM. I choose A3942 from allegro company. Gates of 4 transistors are driven from Gx pins which signals are copies of Inx pins so I can control current across solenoid by uP. I suppose ,there have to be a feedback for sense current across solenoid. Need some or not? Solenoid valves have only two states on/off. I am confused because in datasheet is none.How do I then find out or calculate current? And please, what is suitable concreted transistors(model) for this application you think? I chose this http://www.farnell.com/datasheets/98375.pdf. It's good choice?

    Solenoid parameters: power=3W, volatage=12V

    Thanks for your answers

    •   Alt4th March 2012, 23:42

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    Re: selenoid controlled by PWM

    Dear kovibb
    Hi
    What do you mean by this :
    I need control four solenoid valves by PWM.
    Is your mean H bridge ( four mosfet or IGBT )?
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    Goldsmith
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    •   Alt4th March 2012, 23:46

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  3. #3
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    Re: selenoid controlled by PWM

    it's mean like is illustrated in datasheet i.e four individualy switches for four individualy solenoid valves, no H bridge.



    •   Alt4th March 2012, 23:51

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    Re: selenoid controlled by PWM

    Take a step back and ask what attribute of the solenoid
    you are trying to control. Current? Voltage? Position? Flow?
    Get your mind right about feedback. There's plenty of
    options for power switches, drivers and so on. But these
    are only the nuts and bolts, and I don't see a plan.



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    Re: selenoid controlled by PWM

    Quote Originally Posted by dick_freebird View Post
    Take a step back and ask what attribute of the solenoid
    you are trying to control. Current? Voltage? Position? Flow?
    Get your mind right about feedback. There's plenty of
    options for power switches, drivers and so on. But these
    are only the nuts and bolts, and I don't see a plan.
    OK step-by step:
    some solenoid atributte what i have at the disposal: supply power: 24V, max current: 400mA, solenoid drive current: valve will start open at 80mA and be fully open at 133mA
    feedback: solenoid valves controll flow of air to tyres. I sense pressure in tyres and then send informations to controll unit which drives solenoids by PWM signals. I dont have to sense air flow, because it is dont interested for me but i want to sense currents because of crititcal aplication in automobile.
    more information what i am planing is here: http://www.edaboard.com/thread245624.html



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