AVR-Chat

A pulse won't help you. Vibrated open or short situations
will still be an open or short circuit. I suggest that you
use a steady-state voltage as I suggested in my earlier
post, then digitally filter. That will do a LOT more for
you than pulsing.

Jim

On Tue, 09 Nov 2004 15:21:18 -0000
 "Dave Mucha" <dave_mucha@yahoo.com> wrote:
> 
> Correct, it is a series loop.  
> 
> It is for a machine where the wires can be cut or vibrate
> open or be 
> shorted.
> 
> The current or pulse would offer a more accurate way to
> verify that 
> the switches are in the circuit.
> 
> Dave
> 
> 
> 
> 
> 
> 
> --- In AVR-Chat@yahoogroups.com, Dave VanHorn
> <dvanhorn@d...> wrote:
> > At 09:42 AM 11/9/2004, Dave Mucha wrote:
> > 
> > 
> > 
> > >Hi all,
> > >
> > >I am looking an alarm type switch and am
> thinking of using a Tiny11
> > >to generate a pulse of something like 10khz and
> then send that thru
> > >the 6 to 10 switches (in series) and then use
> the same Tiny11 to
> > >detect that pulse.  Any switch opens and
> the pulse is lost.
> > 
> > This is just a series loop, right?
> > No need for pulses, just give a current of 10-20mA
> and detect 
> open/closed 
> > with debounce of about 100mS. Protection of your
> inputs and outputs 
> is more 
> > interesting.
> > 
> > For a moment, I thought you meant addressable
> switches, as 
> in "which switch 
> > is open".
> > 
> > Years and years ago, I did something like this in
> discrete logic 
> (yecch!)
> > It sent a wide sync pulse, then narrow polling
> pulses down a single 
> conductor.
> > Another conductor carried back answering pulses from
> each switch.
> > 
> > Today, a single Tiny-11 at each switch point could
> work, but you'd 
> have to 
> > program in their address ranges. A micro with more
> pins would allow 
> a 
> > dipswitch to set that. Four pins for a 0-F
> dipswitch, and four 
> switch 
> > inputs, plus two pins for data, would be nice.
> 
> 
> 
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