Re: [uCsimm] SIMM hardware question

From: Ian Leonard (
Date: Wed Feb 21 2001 - 07:44:42 EST

On 2001.02.20 16:38:27 +0000 Jean-Marie Bussat wrote:
> > I am working on a project in which I need to process inputs from a couple
> > relays (i.e. the relay is either open or closed by an external source). Is
> > it acceptable to simply use the relay to feed +3.3V from the uCgardener to
> > one of the PDx pins, or does it need 5V, or is something else needed?
> But, if you plan to use them in an interrupt driven system (i.e. you
> will look for an edge/change of the contact state), you will need an
> "anti-ringging" circuit since when a relay contact closes or opens,
> it doesn't not do that in a very "clean" way. You may have successive
> closing/opening of the contact before it reach its mechanical stable
> state. This may generate spurious interrupts that may confuse your
> program.
> "anti-ringging" circuits can be as simple as a R/C network or it
> can be made using a monostable. It also exists some integrated
> circuits that are doing this job (I dont remember any reference...).

Could you not just wait for a few ms (maybe quite a few) and then test
the input to make sure it's valid?

Ian Leonard                  
Phone: +44 (0)1865 765273       Fax: +44 (0)1865 765280

Please ignore spelling and punctuation - I did. This message resent by the list server

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