[EMS Discuss] Magnetic Device Troubleshooting

Thu Aug 22 18:45:00 PDT 2013

Hello All!

I have a device that I can only say so much about due to an NDA but I am
having a problem with and need a bit of advice. If I have not given enough
info or a diagram (though I cannot be too detailed on certain aspects) is
needed, please let me know.

Thanks so much!

I have Arduino based controller that turns on a single control board input,
which turns on one of 4 individual mosfet banks. When a mosfet bank is on
it allows current to flow which turns on an electromagnet.

The magnets are hooked to the main power bus, all the same way, one side
going to positive and one to negative with a mosfet bank keeping it from
being always on.

There is a bit of something in the magnet connector that is supposed to
cancel backflow EMF that could damage the controller, I am not positive
what is going on with that but it is super simple part wise, and I can get
the part number and post it if needed.

This system used to work correctly in the past the way it is wired, but not
when I had it in my possession.

Problem: When a magnet is activated another magnet is always active at the
same time.

Known Information

   1. The Arduino controller and the control board are working correctly.
   It sends a pulse to the correct mosfet bank. The correct indicator light
   activates and high voltage is sent to the corresponding mosfet bank.
   2. The mosfet banks seem to be working correctly, only the one receiving
   a signal activates.
   3. The magnet that is triggered by the controller does activate(correct
   4. The incorrectly triggering magnet is not triggered through induction
   and proximity does not matter.
   5. The same pairs of magnets always activate, even if rewired to the
   power supply in different configurations(magnets 1 & 4, 2 & 3)
   6. The only way to get a single magnet to activate is to remove it's
   paired magnet from the machine.
   7. The Arduino based controller I built is connected thusly: a ground
   wire to share the circuit's common ground and 4 control wires, each to
   individually turn on the pins on the device control board that drive the
   8. Changing out the Arduino based controller for another control
   method(or manual control) does not change the behavior of the machine

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