Sir i am making a BCD counter.I used HEF4543 for driving 7-segment & MC14553 decade counter.when i give pulse to pin#12 of MC14553 the display shows counting unstable or once pulse gives counting of more than 1. How can i do this that one pulse give only one count? can i use 555 for this purpose? also i want to use an optocoupler so that the interruption in optocoupler will give one count. Please help me.