I have a hopefully simple problem that I'm struggling to solve, I'm pretty rusty at electronics and don't really have the time to re-learn everything I used to know!
Anyway, I have a negative going pulse from a Geiger Counter of about 0.5V and 50 micro-second duration(see attached pic) which I want to 'stretch' by triggering a 4047 chip configured as a retriggerable monostable. I want to use the output of the 4047 to drive a piezo beeper or some such so that each pulse gives a beep. I can't seem to trigger the 4047 with the pulse and I assume it's not quite the right shape being negative going and only 0.5V or so? What I need (I think) is something to invert and possibly amplify the pulse, a transistor inverter perhaps? I'm running the 4047 circuit on a 9V battery and this triggers/retriggers fine when I manually pulse the input so I think that circuit is working fine it's just getting it to trigger using the pulse from the counter.
Any help would be very much appreciated.
Thanks