I think you are getting closer to the solution.  You've shown
that working at the motor seems to help the most.

Remember that bigger capacitors that are rolled or folded inside
have an inductance, meaning that sometimes smaller simpler capacitors can
bypass the highest frequencies better.  In some cases a combination is
warranted.

Don't just keep making the caps bigger, try some of the other
ideas in addition to the caps.

Barry

At 02:05 PM 8/29/01 -0400, you wrote:
>Guys,
>
>         Just wanted to give some feedback on all the suggestions that have
>been submitted.  BTW, there have been a lot of suggestions.  I appreciate
>it a lot.
>         I went through the suggestions and tried them.  Listed below is
>what I tried and how well it worked.
>
>1.      0.1uf cap across relay coil - no help
>2.      4.7ohm resistor in series with relay coil - no help
>3.      Checking all inputs for noise or floating inputs - no help
>4.      10nf cap from C to E on the transistor - no help
>5.      Put 0.1uf cap across relay contacts - partial success.  Instead of
>failing like 75% of the time, it only failed about 10% of the time
>6.      Put two 0.1 uf caps across relay contacts (in parallel) - better
>partial success.  Failed probably 5% of the time.
>7.      Moved the caps to the terminals right on the motor - better
>success.  Failed probably 1% of the time.
>
>         I'm saying failure is when the PIC resets or jumps to a random
>place in the code.
>         So, I'm thinking if I put a bigger cap on the motor winding
>terminals, it will help even more.  Question is, how big of a cap should I
>use?  I can't use an electrolytic b/c the motor reverses direction.  Anyone
>have a suggestion?  Hopefully something fairly cheap.
>
>Thanks,
>
>Gary
>
>
>At 02:55 PM 8/28/01 -0400, Dan Michaels wrote:
>>Gary Neal wrote:
>> >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.
>>.......
>>
>>
>>Sounds like you need a suppressor across the relay "contacts", or
>>better yet at the motor itself. Since a DC motor, try a reverse
>>diode there or a snubber - 10-100 ohm resistor in series with a
>>0.1 uF cap across the motor winding. The cap should be better
>>quality than simple low-V ceramic. 200V or so polypropylene.
>>
>>- dan michaels
>>www.oricomtech.com
>>========================
>>
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