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Footswitch actuated solenoid

  1. Apr 30, 2010 #1
    I have a toy that is mounted 4 feet above the floor on which there are 3 pushbutton DSTP switches that I would like to actuate intermittently with my feet.

    I believe that I can do this by building a device that pairs 3 appropriately positioned solenoids with 3 momentary SPDT footswitches all connected in parallel to an AC/DC adapter with an on/off switch plugged into a wall outlet.

    I tested the force required to actuate the pushbutton DSTP switches and found it to be 2.15 lbs with a 0.125" stroke. Adding a 50% factor to this I would need a solenoid capable of producing 3.2 Lbs over a 0.187" stroke.

    I found a low profile medium stroke conical face push or pull solenoid whose rated force at 10% duty cycle for the required stroke is capable of producing 3.6 lbs. Manufacturer specifications organized under the 10% duty cycle column includes 90 Watts, 1690 amper turns, and when choosing a VDC of 10.4 [chosen because it is the closest to 12v DC] it continues 24 AWG, 1.18 resistance, 192 number of turns, and a dielectric strength of 1000 VRMS. My guess is that if I divide the 1690 amper turns by the 192 number of turns that equals 8.8 A. Its physical dimensions are ideal for my application.

    I have preliminarily chosen a foot switch whose manufacturer specifications include the following: contact form SPDT-NC/NO; current rating 15A; IP rating IP20; operation momentary, voltage rating 250 VAC; UL recognized, CSA certified.

    I have preliminarily chosen a power supply adapter whose manufacturer specifications approximates the wattage, voltage, and amperage of the above referenced solenoid as follows: voltage input 100 to 240 VAC; output 12 VDC at 8.3 Amps; power output 100 W, over voltage, over current, and short-circuit protection built-in. It also has an 8-pin output cord which has 4 pins assigned to +V1 and 4 pins assigned to Return. My belief is that I would use 3 of these pairs of pins [+V1 and Return] connected independently to each of my 3 solenoid footswitch pairs.

    I would welcome any engineers opinion regarding my methodology and conclusions. Am I correct in my analysis and selection of the power supply? Will this work?
  2. jcsd
  3. May 1, 2010 #2
    Ok, I'm a little confused as to what you want to do with the solenoids... operate DPST remotely using solenoids & actuators?

    I'm not sure, but a 90 Watt solenoid for 3.6 lbs of force seems a little excessive... We're using a 3.5watt solenoid (coil current of 300 mA) to change gears in a high performance race car. What kind of line pressure were you thinking of? What actuators? (All this is assuming you're thinking pneumatic)
  4. May 1, 2010 #3
    Thank you for your reply. I don't know what an actuator is, but otherwise yes.

    The manufacturer specifications rate the solenoid from 90 W for 10% duty cycle all the way down to 9 W at 100% duty cycle with a corresponding decrease in force capability. My guess is that the higher the frequency of use, the warmer the solenoid gets and the lower the power output. The other possibility is that I misinterpreted the manufacturer specifications and have chosen a solenoid that is overkill for the task at hand. However I don't know how else to interpret their charts and graphs. Please see attachment for the 3EC.

    No, this is not pneumatic, it's all electric. Just step a foot pedal to close the circuit and charge the solenoid.

    Attached Files:

    Last edited: May 1, 2010
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