Need a simple, one-shot circuit

I need to build a circuit that, after receiving a relay input, provides a momentary dry contact closure. I will need to use parts that are readily available (from Radio Shack or equiv). I would also like to build a second circuit that provides a 30-second (rather than momentary) contact closure. I am unable to design these circuits myself, but can follow directions that don't assume anything but basic electronic knowledge on my part. I would very much appreciate any help I receive, and will be happy to let you know the outcome of the project.
Thanks very much

For a quick, cheap, reliable one-shot circuit, it's hard to beat a 555 timer chip in monostable mode. The circuit only takes a couple of resistors and capacitors along with the 555 chip. Add a relay and voila! there you have it. Here's a link to a datasheet for a 555 chip from National Semi https://www.electro-tech-online.com/custompdfs/2004/11/LM555.pdf. You could likely get the same info from the datasheet section of the forum on the main page.
A diagram for the monostable (one-shot) circuit is on page 7 of the pdf datasheet. Connect your relay coil from pin 3 (output) to ground (as the normally off load) and change the component values of Ra and C to give the length of time desired.
Hope this helps.
JB

Yes ...

but in monostable mode, it requires a high-low-high pulse to get it to fire once.

To get the chip to fire once on power up, put a resitor from pin 2 (trigger) to VCC and a capacitor from pin 2 to ground. 100uF and 2.2K are values that have worked well for me.

Thx to k7elp60 for helping me out with this problem in this topic:
https://www.electro-tech-online.com/threads/winpicprog.11561/ - Also JB