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Pulsating Valve-circuit. Controllable impulses

  1. Nov 20, 2011 #1
    So I have this valve(see attachments).

    That valve is basically an inductor. It works at 24V DC, rated 5W. At third picture you will see a piston. This is all about 8 cm long (3rd picture including the piston). Just to give you the feeling of size.

    How this piston has to work:

    It gets an impulse, it attracts the ferromagnetic inside. Lets call that "on" state. After that the circuit goes into off mode, and that little spring that you see at 3rd picture pulls the piston back.

    My questions:

    1.Having on mind that 24V DC isn't much, could I use something like 555 timer to get these signals?

    2. I have to be able to control the number of pulsations per second. Ideally through some pot. Is this possible with 555 timer?(I am really new to 555 timers, but understanding them shouldn't be a problem). We are talking about range of 2-15 impulses per second.

    3. If 555 timer cannot handle these kinds of voltages, should I use some relay? Are we raising the question of response time?

    I am also aware that I should install the flyback diode, to get better response.

    Any suggestions are more than welcome.

    Thank you

    Attached Files:

  2. jcsd
  3. Nov 20, 2011 #2


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    Science Advisor

    A 555 would not be able to directly drive an actuator like that. They have an upper voltage limit of 18 volts and a current rating of 200 mA. In practice, you would not use more than 75% of these limits.

    You can work out the current it will draw.
    Power = Voltage * current
    so current = power / voltage
    = 5 W / 24 V
    = 0.208 amps
    You can use a 555 to generate the pulses and then use these pulses to drive a power transistor or power FET.

    Like the drawing below, except you may drive the actuator directly or with a relay as shown:

    [PLAIN]http://dl.dropbox.com/u/4222062/relay%20driver2.JPG [Broken]

    The problem then may be that the actuator might have trouble reacting 15 times a second.
    Last edited by a moderator: May 5, 2017
  4. Nov 21, 2011 #3
    Hmm a BJT for this? I was thought that they have slow response time compared to FETs.

    I would go for power FET then, if my assumption is right. Are power FETs a lot different from normal FETs?

    Because, when I had to learn them, my material was really poor and only went so far explaining them.

    So this is called actuator :D
    I didn't know that. I was just given the component, I was told what it does and I was told what it is meant for.

    I am going shopping for 555 timer tomorrow, so can you be more specific about this power FET so I can get that too?
    Last edited by a moderator: May 5, 2017
  5. Nov 21, 2011 #4


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    Science Advisor

    I have some BJT transistors that work up to 6000 MHz. So, no, they are not slow at all.

    FETS come in enhancement and depletion mode types and power FETS are usually enhancement mode MOSFETS.

    From a practical point of view, this means that they have to have about +3 V on the gate (relative to the source) to turn them on.
    This varies and some need more than 5 volts, which means you can't drive them with a 5 V circuit.

    Ask at the store for an enhancement mode power MOSFET then get a big one with a built-in diode to protect against high voltages.
    You may have to get insulators and a heatsink as it is probably going to get hot.
  6. Nov 22, 2011 #5
    Thank you very much kind sir.
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