RE: Making a mains relay pulse - electronics Q

["Ian" <ian.bird@xxxxxxxxx>]

My initial thoughts here would be to use your output to trigger a 555
circuit which would then do the one second bit.

<http://www.mollyology.com/ProjectsBabyPaws.htm>
http://tinyurl.com/26escc

This is something I built to extend an output pulse but should give you a
starting point at least. It may even do what you want out of the box.

Fire any more questions over no problems. I probably even have all the
components if you would like them. I don't tend to use this stuff these
days. It's all surface mount and microprocessors now.

Good luck

Ian

> -----Original Message-----
> From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx]On Behalf Of
> David Chapman
> Sent: 23 June 2007 14:17
> To: ukha_d@xxxxxxx
> Subject: [ukha_d] Making a mains relay pulse - electronics Q
>
>
> Automated Home DiscussionI'm sure this is not too difficult but I
can't
> figure out how !
>
> As part of a bit of HA I've got an output (from a PIR exterior light)
at
> mains level that I think is transistor switched (can't hear a
> relay)  What I
> want this to do is close a couple of contacts on a switch at 5v
> level - that
> bit is quite easy, mains relay, but I want it to pulse the relay just
for
> one second rather than holding it closed and the problem is the
shortest
> time I can get the PIR to switch for is about 30 seconds.
>
> I guess what I need is a capacitor - somehow - that maybe lets through
an
> initial pulse ?  Also how do I then protect the output of the PIR
> ? I think
> just a mains rated diode on the output would do the job ?
>
> Any ideas or clues ? I did have a link to a website with loads of
little
> circuits like this but I can't find it.
>
> David C
>
>
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