Marbles
Posts: 3
Joined: Wed Oct 12, 2016 8:48 pm

Electromagnetic Interference on RUN header

Wed Oct 12, 2016 9:05 pm

Hi,
I have a Pi 3 with a shutdown button (incl pulldown resistor) and a button to restart it again - This one is connected to the RUN header to reset it after it was halted with the shutdown button.

The buttons are connected via wires less then 10 cms long.
The Pi turns out to be sensitive to Electromagnetic Interference. Whenever I switch on/off a 220V device that is (very) near the Pi, the shutdown GPIO detects false inputs. I have solved this in code requiring longer contacts from the button before the script runs the halt command.

However, I also have this problem on the Run header. If I put a 220V lamp on top of the Pi and start switching it on and off, it will actually cause the Pi to reset. If I remove the button wires from the header, it doesn't happen. So I'm assuming I'm causing a current in the short wires that is enough to drop the voltage on the Run header which make the Pi reset.

My question: I know that adding pullup/pulldown resistors and capacitors in various ways to the GPIO headers can solve the interference there - But how do I protect the run/reset pin? Can anyone suggest a circuit?

Thanks!

georgian
Posts: 15
Joined: Wed Oct 12, 2016 8:13 pm

Re: Electromagnetic Interference on RUN header

Wed Oct 12, 2016 10:44 pm

Maybe some TVS diode can help. Or well shilded cable should work too.

jdb
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1763
Joined: Thu Jul 11, 2013 2:37 pm

Re: Electromagnetic Interference on RUN header

Fri Oct 14, 2016 12:43 pm

Use an opto-isolator for switching the RUN pin. Supply the diode side of the isolator from the Pi's 3v3 input, connect the phototransistor across the RUN header.
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