Re: Looking for a Low Cost On Delay Timer

["Guv Bob" <guvbob2003@xxxxxxxxxxxxxxxxxxxxxx>]

"unruh" <unruh@xxxxxxxxxx> wrote in message =
news:lAHSt.180556$po1.28313@xxxxxxxxxxx
> On 2013-08-26, Guv Bob <guvbob2003@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> > "Guv Bob" <guvbob2003@xxxxxxxxxxxxxxxxxxxxxx> wrote in message =
news:1_udnQ7rBpNjRo7PnZ2dnUVZ_sidnZ2d@xxxxxxxxxxxxxxxx
> > Names can be confusing, so here's what I'm doing....
> >>
> >> http://img43.imageshack.us/img43/7434/wvm.gif
> >>
> >> When 12VDC is applied to the input, I need a 12VDC output for 5 =
seconds.  Then output will go back off and stay off until the input goes =
to zero.  Then cycle starts again.
> >>
> >> Current for both legs is in the 10-50ma range.
> >>
> >> A simple on-delay timer would work but I'm having trouble finding =
one with NC contacts.  Tons of stuff $100+, but for this application, it =
has to be under $20.
> >>
> >>=3D=3D=3D
> >
> > Thanks for all the tips and good info.  I had wanted to put =
something together from components but my brain is too far behind these =
days.  I'm going to give this a shot and hopefully I'm not picking the =
wrong one.  It's $5 at Frys...
> >
> > Velleman MK111
> > =
http://www.vellemanusa.com/downloads/0/minikits/manuals/manual_mk111.pdf
>=20
> Except that looks like an oscillator rather than a "oneshot"=20
> You said that you wanted something that if the input was larger than 5
> sec, the output would go high for 5 sec, and then drop to 0. If the
> input droped before 5 sec was up, you wanted the output to drop as =
well.
> Then you wanted it to wait until the input went high again before =
doing
> that again.
> This device has a relay (why would you need a relay for 50ma? Most ICs
> can handle an ouput current of 50mA at 12V without the need of a =
relay.
>=20
> This kit is an oscillator, where you can adjust the time it is on and =
the
> time it is off with the pots. It has no input.=20
>=20
> It uses a 555 timer chip. The primary design of the 555 is to initiate =
a
> pulse when the input goes high, and stays high for the requsite time
> even if the input drops again. If the input stays high beyond the time
> Ie, I think you want to think your way through what you need =
carefully.

Thanks, yes you're right.   What value resistor could I substitute for =
RV1 to give a pause time between pulse to 10 minutes?