0 to 16 hours non-class time controller circuit using NE555 and CD4040
1 hour timer circuit with LM122
1 to 99 countdown divider or countdown circuit
4 hours of AC power timer circuit using 555 and BH4024
5G28 based automatic exposure timer circuit with amplifier
6-60 second timer circuit
9 hours to 1 second countdown music reminder circuit
9 hours to 120 seconds countdown music reminder circuit
74LS85 based delay comparator circuit a
74LS85 based delay comparator circuit b