> Hello,
>
>         I've got a 16f870 that I'm using to turn a relay (Tyco V23105
>         150 mW
> Nominal Coil Power, 960 ohm, 12 volt Nominal Coil Voltage) on/off.
> This relay is controlling a very small DC motor (~0.5amps).  About 10%
> of the time when this relay turns on/off, it resets the PIC.  I've
> verified this is what's happening.  Seems to work fine when the motor
> isn't connected to the relay.  Only resets when the motor is
> connected.
>         I'm using PORTA.0 through a resistor to turn on a 2N4401
>         transistor that
> then powers the relay coil.  I have a 1N4004 diode across the relay
> coil.  I have two 0.1uf caps on the +5v to the PIC.
>         The +5v for the PIC is from a powered protoboard.  The +12v
>         for the
> transistor and relay are from a +12v battery.  The grounds of these
> two power supplies are tied together.
>         Can anyone help me figure out what's going on and fix this?
>
> Thanks,
>
> Gary

Hi Gary,

It may be worth trying a 1N4148 diode in place of the 1N4004, as it
is much faster switching diode. All the suggestions so far have
been good, so figure out which one fixes the problem and then add
all the others as extra safeguards. That my 2 cents worth.

Brent Brown
Electronic Design Solutions
16 English Street
Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/text: 025 334 069
eMail:  brent.brown@clear.net.nz

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