Simple Solenoid Stuff

Discussion in 'The Projects Forum' started by ScannaMan, Mar 27, 2009.

  1. ScannaMan

    Thread Starter New Member

    Mar 27, 2009
    Hi I'm trying to activate a home-built solenoid with my computer. Here's what I have so far:
    1) the solenoid is just a plastic pen with about 50' of thin wire wrapped around it. There is a smooth steel rod in the pen which works as the piston. When I apply 12 volts to the wire ends, the piston goes up. Turn the voltage off, it drops back down. Yea.
    2) I have a solid state relay connected to my parallel port and the solenoid. Using a program I found (ksi8.exe) I can send a 3 volt signal from the parallel cable by pressing a number on the keyboard.
    When I hit the right key, this closes a circuit on the relay and voltage can pass through to a light or a motor and it works! On, off, on, off, all day.
    BUT...with the solenoid, it activates but won't turn off when I turn off the signal from the parallel cable. Just stays humming in the up position until I turn the power off. The SSR is a Crydom CX24D05 and works with other 12 volt DC thingys, but not the solenoid.
    That's all there is. I'll try to attach a crude illustration. Just wordering why it sticks on. Much obliged for any help.
    Last edited: Mar 27, 2009
  2. eblc1388

    Senior Member

    Nov 28, 2008
    Can't locate datasheet for CX24D05. Could it be the CX240D5 instead?

    If so, then the device is for AC load only. AC is needed because the device will not turn OFF if DC is used.

    It works for low current devices with 12V DC because the load current is low enough for the internal SCR(s) not to latch ON so it turns off when your input signal is removed. If the load current is higher than the latching current, like in this case of a solenoid coil, then the SSR will latch ON and does not turn off.

    I can't offer a solution using the existing SSR but you can either:

    1. use a transistor or MOSFET to replace the SSR and get the same control function instead. The NPN or MOSFET need to be able to take the full current of the intended load. However, this does not provide electrical isolation like a SSR does.

    2. drive a small 12V relay using a small NPN or MOSFET and then drive the solenoid using the relay contacts.
  3. michael_j_w

    New Member

    Mar 26, 2009
    Make sure to add a diode to protect everything from the voltage spike of the relay coil.
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009