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Driving 3Amp solenoid with BS1 — Parallax Forums

Driving 3Amp solenoid with BS1

gartogarto Posts: 1
edited 2005-02-04 22:50 in General Discussion
Okay first post...bear with me...
I'm making a board for my paintball gun, my code is like 5 lines long (thank god for button command) but my question is how exactly to I drive the solenoid. I have been using the board of education with no luck in this. I am using a irf510 power mosfet from Radioshack (part 276-2072). I believe the solenoid uses 3 amps which is under the posted 4 maximum but i could be wrong. Also the mosfet uses source, drain, and gate terminals. I'm new to electronics so please post to where do these terminals go. I believe gate would go to the output pin of the basic stamp and solenoid would be hooked up between the batteries positive terminal and drain with source to the negative terminal. I have two mosfets also is there anyway to use them both to boost max current capabilites?
············· thanks,
·············· Chris

Comments

  • blink13blink13 Posts: 65
    edited 2005-02-01 23:12
    i am doing an almost identicle prodject.i think that you just apply power to the solenoid thats what i heard from someone. i need help with a program will you post yours, i am prototyping with a homework board.
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-02 06:13
    hook it up like Jon has in his illustration in this thread: http://forums.parallax.com/showthread.php?p=521472
    ·with the solenoid taking place of the motor, and yes you can tie all similar terminals of two transistors together to get more current capability.
  • PLJackPLJack Posts: 398
    edited 2005-02-04 19:35
    Ok, Question.
    I used the schematic listed here www.awce.com/fetrly.htm to build my Mosfet / solenoid board.
    I see that Jon has a second resistor in his circuit. (first picture).
    The second image is my circuit. The stamp pins are the top connectors. The solenoid grounds go on the bottom connectors.
    It seems to work fine, what is the second resistor in Jon's image all about?

    Post Edited (PLJack) : 2/4/2005 7:43:44 PM GMT
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  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-04 20:30
    It provides a slight decoupling between the stamp output pin and the mosfet, the gate of the mosfet acts as a capacitor that needs to be charged when the mosfet is turned on. The series resistor decouples the output pin's voltage and the voltage at the gate, this reduces the effective capacitance seen by the pin and allows the pin to have a higher slew rate (how fast the voltage rises). This resistor is not critical, it just helps ensure the stamps drive characteristics are in spec. The larger the drive characteristic of the mosfet, the more important this is because the larger the amperage handled by the mosfet, the larger the transistors dimension, the larger the gate capacitance. But if your design is working, I wouldn't worry about it.
  • PLJackPLJack Posts: 398
    edited 2005-02-04 22:50
    Thanks for clearing that up Paul.
    If if the PCB starts to act up then I will have something to fall back on.

    Great info, thanks.

    Jack
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