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FTDI USB Interface tripping out

Discussion in 'General Electronics Discussion' started by mikeyk, Feb 12, 2011.

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  1. mikeyk

    mikeyk

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    0
    Feb 12, 2011
    Hi we are having problems with interference to an FTDI USB interface chip which is locking up and cutting off communications

    The FTDI chip is integrated on a PCB which drives a number of components including a solenoid valve and gas igniter. When the solenoid valve is activated and then deactivated it trips out the chip every time, the gas igniter which creates a spark trips it out every 3 or 4 times but not consistently

    There are options of reducing EMI interference through various means but none appear to give a guaranteed solution. It seems the FTDI chip is just too sensitive to this type of interference and wonder if anyone can suggest an alternative interface?

    Many thanks
    Mike
     
  2. mikeyk

    mikeyk

    3
    0
    Feb 12, 2011
    The connection that is tripping out runs from the computer to the FTDI chip, but the interference appears to be airborne. We tried a separate ignition module that was powered by a completely independent circuit. If it was within a metre of the circuit containing our USB connection when it ignited, it would trip it out.

    So shielding is one option (although we will always need holes for the USB cable and other interfaces to go through).

    We just wondered if the FTDI chip was known for being sensitive to this type of interference, or if any USB interface would be the same.

    Maybe RS232 is the better interface for this type of application?
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,299
    2,737
    Jan 21, 2010
    If you are getting interference when a solenoid opens (i.e. power is removed from it) then I would check that I had a reverse biased diode connected across the solenoid's coil to absorb the inductive spike you will get if you try to instantly stop the current.
     
  4. mikeyk

    mikeyk

    3
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    Feb 12, 2011
    Sorry, should have added an update on that. The solenoid problem has been solved with a diode. The spark ignition module is proving to be more of a problem though as it is airborne interference.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,299
    2,737
    Jan 21, 2010
    You might like to try placing inductors in series with he long leads exiting your device (or ferrite beads) and perhaps even small capacitors from signal to earth to attenuate the signal. You may need to go as far as to shield your device.
     
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