This question is related to another one . However, rather than resurrecting an almost two year old thread, I preferred to create a new one.
So I have this circuit (the same one as in the previous question, which was taken from here. Basically, a quiz show system, in which only the first contestant to press the button gets his LED to turn on.
The original circuit was designed for a 9V input power supply, and it seems to work fine with it. However, I need to make it work with a 5V one. The 555 (NE555 in my case) supports anything from 4 to 14V, so that should be OK.
However, as soon as I run it on 5V, it becomes... unstable. Meaning that a 555 might trigger if I simply touch one of the trigger contacts with my hand, or a metal object. Even worse, more than one 555 will trigger at the same time.
It looks like the "high" voltage on the trigger line is no longer enough to prevent the line from going low for long enough to trigger a second 555. The actual values look like this: with a 5.7V Vcc, the output (pin 3 of the active 555) goes to 4.1V, and the trigger line to 3.4V.
Unfortunately, I am quite... inexperienced with this, so I am stuck. Can anyone give me some tips on what I could do to make the circuit stable with the new Vcc?
Thank you!
So I have this circuit (the same one as in the previous question, which was taken from here. Basically, a quiz show system, in which only the first contestant to press the button gets his LED to turn on.
The original circuit was designed for a 9V input power supply, and it seems to work fine with it. However, I need to make it work with a 5V one. The 555 (NE555 in my case) supports anything from 4 to 14V, so that should be OK.
However, as soon as I run it on 5V, it becomes... unstable. Meaning that a 555 might trigger if I simply touch one of the trigger contacts with my hand, or a metal object. Even worse, more than one 555 will trigger at the same time.
It looks like the "high" voltage on the trigger line is no longer enough to prevent the line from going low for long enough to trigger a second 555. The actual values look like this: with a 5.7V Vcc, the output (pin 3 of the active 555) goes to 4.1V, and the trigger line to 3.4V.
Unfortunately, I am quite... inexperienced with this, so I am stuck. Can anyone give me some tips on what I could do to make the circuit stable with the new Vcc?
Thank you!