Troubleshooting an Arp Sequencer

[Jim Johnson]

Nah, the switch is already debounced. It is only when the jack panel board
- an entirely passive board, nothing but jacks and an LED - is connected,
that the switch bounces. And when I unsoldered the jack that connects to
the circuit, the problem went away, which is why I suspect parasitics in
the jack. Which is wierd.

*********** REPLY SEPARATOR ***********

On 5/10/98, at 11:58 AM, Brian Towles  wrote: 

>Jim Johnson wrote:
>
>> I'm trying to repair an Arp sequencer using minimal tools - no scope -
and
>> I've run into something I can't understand.
>>
>> This problem has to do with the Step circuit. When everything is
assembled,
>> pressing the Step button causes the sequencer to advance, pretty
>> consistently, by 11 or 12 steps. However, when the jack panel board
>> containing the Step input jack is removed, it works correctly.
>
>Could the switch be bouncing?  I don't know anything about the particular
>setup, but that's what it sounds like to me.
>
>Feeding the switch output directly into a digital input usually gives
>multiple rising and falling edges as the switch makes contact.  If the
>circuit is edge-triggered this is a major problem.  One solution is a
>so-called "debouncer" circuit.  The circuit basically synchronizes the
>switch's output with a slow clock ( 10-500Hz ):
>
>
>  +5 -----    input      D Flip-Flop
>           \  switch     |--------|
>            -------------|D      Q|----------- debounced signal
>                         |        |
>  GND ----               |  Clk   |
>                         |--------|
>                             |
>                             |
>                       "slow" clock
>
>There are other solutions to this same problem, maybe a LP fliter for
>example.  Hope this helps.
>
>Brian

Jim Johnson 
Metaphoric Software
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