lavenatti
Member
I have a ST brand NE556N I've used to construct a missing pulse detector (see attached). It works just fine when using the ST IC. I stick something in between the LED emiter and the NPN optical transistor to temporarily break the beam and the output LED comes on for a second or so and turns back off. When I switch to a another brand of 556, I've tried NE556 from Samsung and an LM556CN from National - neither circuit triggers. The output pulse train to the LED works fine, I checked with a Oscilloscope. The second timer can also be manually triggered with a negative pulse (touched to ground) and seems to work just fine. It just won't trigger with the same input.
Any suggestions?
Any suggestions?