[NCARC] Need help debugging electronics project

[Dave hartzell]

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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