555 Monostable question

Hi, I am trying to build a circuit that when a voltage is present on a line in one circuit it will momentarily trigger a switch (essentially push and release a button) on another circuit. I tried setting up a monostable 555 circuit, but if the trigger switch isnt released, the light I am using to simulate the relay that will be used to "push" the button just stays on indefinitely. I guess what I am trying to do is instead of using a momentary push-on to trigger the timer, I want to use a SPST relay but still have the output from the timer be a pulse and not just stay on. Is this possible? If this made no sense please let me know. Thanks!

Sounds possible. Why not post your circuit so we can see what you're doing?

The simplest pulse generator I can think of is a capacitor in series with the first circuit (the one you want to set the whole thing off). When power is applied, it will generate an exponentially-decaying pulse. Of course, you need to discharge the capacitor to prepare it for the next cycle; this can be done just with a bleeder resistor (a high resistance to drain of the charge gradually), depending on cycle time.

Here is what I am trying to do, except the way it's set up the relay on the circuit furthest right would just stay on indefinitely and not momentarily like I want it to. Ignore the math on the top left, the voltages are arbitrary right now, and I haven't worked out exact timing yet so theres no values for the resistors or capacitors, but this shouldn't really matter at this stage. Thanks for the help.

**broken link removed**

hi,
AC couple the 555 Trigger input, see modified circuit.

What is the specification of the relay coil.???