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Problem triggering 4047 monostable with pulse


Oct 16, 2015
Oct 16, 2015
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 the pulse and maybe increase it's voltage to a suitable level to trigger the 4047(?).

The 4047 circuit works fine when I trigger it manually so no problem with that, it's just getting it to trigger using the pulse I have. I'm powering the 4047 with a 9V battery.

Any help (with pictures please!) much appreciated.



  • Pulse out.jpg
    Pulse out.jpg
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