[NCARC] Need help debugging electronics project

[Dave hartzell]

oops, "sync" should be "sink" in this case.

I have to stop thinking digital.  ;-)


On Wed, May 30, 2012 at 11:57 PM, Dave hartzell <hartzell at gmail.com> wrote:
> I have used one of these boards before, with decent results:
>
> https://www.sparkfun.com/products/20
>
> Perhaps the link to the schematic might help.
>
> This design uses a diode and light-emitting diode on either side of
> the relay, and a BJT for controlling the relay (probably since the PIC
> can't sync all the current needed, but it also offers some isolation).
>
> Which makes me wonder, can the basic stamp source/sync all the current
> needed to run the relay coil?
>
> Dave
> AF6KD
>
> On Wed, May 30, 2012 at 10:52 PM,  <scomind at aol.com> wrote:
>> Hi Ed,
>>
>> So each blink is a 12V relay opening and closing? Does sound kinda like inductive kick from the relay coils. The diodes help but you might still be introducing noise into the +12V. But the stamp probably has a 7805 or similar regulator to reduce the +12V to +5, and that should buy you some noise isolation, unless it's the ground that's moving with the noise. Which relay lead do you touch to fix it, the +12V side or the driver transistor side? Have you terminated all IRQ, NMI, and similar inputs so they can't act as antennas and make the processor jump the track?
>>
>> If I were building it I would use solid-state relays. Expensive to buy at retail, but lots of surplus brokers have them. You gain zero-crossing switching that way, too -- less EMI.
>>
>> 73,
>>
>> Bob, WA9FBO
>>
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>>
>> -----Original Message-----
>> From: Ed Gage <edgage at gmail.com>
>> To: NCARC Reflector <ncarc at mailman.qth.net>
>> Sent: Wed, May 30, 2012 3:46 pm
>> Subject: [NCARC] Need help debugging electronics project
>>
>>
>> I've developed a relay control based on the Basic Stamp, and need help
>> debugging it.  There is either some transient noise produced by the relays,
>> or some sort of surge.  I've put a diode across the coils which helped
>> control it somewhat, but I'm at a loss as to what is happening.
>>
>> On powerup, 8 relays are charged with 12V, to drive 120V that runs 8
>> incandescent light bulbs.  The same 12V powers the Basic Stamp, which
>> controls the relays based on input from 8 buttons.  The project is a
>> "lock-out" game, where first press gets solid lamp, 2nd gets fastblink, and
>> 3rd gets slowblink.  Additional buttons get no blink.  A reset to the Basic
>> Stamp resets the lock-outs.
>>
>> What happens is when the second and third buttons are pressed, after
>> several blinks, sometimes the system resets itself, without user input.
>>  I'm at a loss as to why this happens.  However, I discovered I could
>> prevent the reset by touching one of the two leads for the relay.  My
>> assumption was that I was suppressing some sort of electric surge that was
>> happening with my body acting as a conduit to ground.
>>
>> Perhaps somebody could elaborate on why this phenomenon occurs?
>>
>> Anyone willing to come help would be treated to a nice dinner.
>>
>> --Ed Gage, NØTVQ
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