<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; ">I haven't played with the 555 for a long time but basically you want a 556 chip. The first chip is configured for Astable operation and its output is feed to the second timer which is configured for Monostable mode.<DIV><BR class="khtml-block-placeholder"></DIV><DIV>See this site:</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><A href="http://www.electronics.dit.ie/staff/mtully/555%2520folder/555%2520timer.htm">http://www.electronics.dit.ie/staff/mtully/555%20folder/555%20timer.htm</A></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>-John</DIV><DIV><BR><DIV><DIV>On May 24, 2007, at 3:25 PM, John wrote:</DIV><BR class="Apple-interchange-newline"><BLOCKQUOTE type="cite"> Acuracy is not critical. About 15mins is good.<BR> <BR> John<BR> <BR> Stephen Brown Jr wrote:<BR> <BLOCKQUOTE type="cite" cite="middd22fa9c0705241142h5b9fe400h818b11d59e9711b0@mail.gmail.com">I don't have much experience with a 555 or a PIC for that matter, but I would seem to think a PIC would be easier to implement and possibly more accurate. <BR> <BR> Just a thought.....<BR> <BR> 73's<BR> Stephen<BR> K1LNX <BR> <BR> <BR> <DIV><SPAN class="gmail_quote">On 5/24/07, <B class="gmail_sendername">John</B> <<A href="mailto:johnk.mchugh@att.net">johnk.mchugh@att.net</A>> wrote:</SPAN> <BLOCKQUOTE class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">I am in need of a schematic (or complete unit) for a timer that will run<BR> off +12v and pulse a relay every 15 mins. The relay should stay on for<BR> 10secs. I think it can be done with a dual 555, one for the 15mins and<BR> the other for10secs.<BR> Anyone got any ideas. I need this to turn on the TNC and Transmitter for<BR> a solar powered wx station I'm trying to build<BR> <BR> Thanks<BR> <BR> John<BR> <BR> --<BR> John Mc Hugh, K4AG<BR> Coordinator for Amateur Radio <BR> National Hurricane Center, WX4NHC<BR> Home page:- <A href="http://www.wx4nhc.org">http://www.wx4nhc.org</A><BR> <BR> <BR> <BR> _______________________________________________<BR> aprssig mailing list<BR> <A href="mailto:aprssig@lists.tapr.org">aprssig@lists.tapr.org</A><BR> <A href="https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig">https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig</A><BR> </BLOCKQUOTE> </DIV> <BR> <PRE wrap=""><HR width="90%" size="4">_______________________________________________
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John Mc Hugh, K4AG
Coordinator for Amateur Radio
National Hurricane Center, WX4NHC
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