555 Astable and Monostable

Thread Starter


Joined Jun 5, 2007
Hello guys,

Im building a Counter using a 4510 Decade Counter to count from 0 to 50 in 2 7 segments. Now the problem that Im having is that I want to be able to perform the counts manually and automatically. I built 2 555 circuits, one astable that gives me a 1 sec clock and the other monostable so when I push a button, it produces me a clock to get the counter up or down. Im using a 2 position switch with 3 pins. At the ends I have the 555s and in the middle of the switch i have the cable that goes into the 4510 circuit. Works fine, but here is the "problem" If I have a number in display and switch from manual to automatic or the other way, if the movement of the switch its slow, the counters go crazy. Is there a way to fix this?

I tried to put both circuits to the same pin in the counter but does work, it does nothing in the counting. I also put 2 diodes at the end of each 555 so one signal doesnt bounce back to the other 555, but the 4510 goes wild also.

Any other Ideas?

Best Regards


Joined Apr 27, 2007
What seems to be affecting your circuit is some kind of "bouncing" (although that is not the term, because it applies only to buttons, and refers to contact vibration). Your problem is when you switch the circuit very slowly your switch breaks and makes contacts very quickly. So your counter will count randomly and very fast.

Thread Starter


Joined Jun 5, 2007
One quick question btw, If I want that the rest of the counts starts in 1 instead of 0, Do I have to represent a binary 1 at the inputs ports of the 4510?


Joined Feb 24, 2007
One sugestion I would make is to use your switch to Reset your 555's, one position resets the Mono while the astable runs, the other position the mono runs while the astable is reset, and feed both outputs thru an OR gate to the clock in your 4510's


Joined Jun 18, 2007
I came across this thread because I was trying to solve the same problem. My solution was to generate a pulse through a 555 monostable configuration generated from a tsop311 infrared receiver. No bounce. works perfectly. What I also want to do is use a matched pair of infrared receiver and transmitter diodes as the trigger to a passive counter tabulated on 7 segment leds but so far I have not been able to generate a reliable 555 pulse.