24 Hour Timer Circuit

Description: These two circuits are multi-range timers offering periods of up to 24 hours and beyond. Both are essentially the same. The main difference is that when the time runs out, Version 1 energizes the relay and Version 2 de-energizes Continue reading

Asymmetric Timer Circuit

Description: A timer circuit with independent mark and space periods. Circuit diagram Notes: A simple astable timer made with the 555, the mark (on) and space (off) values may be set independently. The timing chain consists of resistors Ra, Rb Continue reading

5 to 30 Minute Timer Circuit

Descriptipn: A switched timer for intervals of 5 to 30 minutes incremented in 5 minute steps. Circuit diagram Notes: Simple to build, simple to make, nothing too complicated here. However you must use the CMOS type 555 timer designated the Continue reading

Periodic Timer Circuit

Description: A switched timer with equal make and equal space periods timing adjustable from over 6 minutes to 38 minutes. Circuit diagram Notes: This timer circuit is similar to the 5 to 30 minute timer except that when switch S1 Continue reading

Timed Beeper Circuit

Beeps 7.5 seconds after a preset time Adjustable time settings: 15 sec. 30 sec. 1 min. 2 min. & others Circuit diagram Parts: R1 220R 1/4W Resistor R2 10M 1/4W Resistor R3 1M 1/4W Resistor R4 10K 1/4W Resistor R5 Continue reading

Tan Timer Circuit

Six timing positions suited to different skin types Timing affected by sunlight intensity Circuit diagram Parts: R1 47K 1/4W Resistor R2 1M 1/4W Resistor R3,R5 120K 1/4W Resistors R4 Photo resistor (any type) C1,C3 10µF 25V Electrolytic Capacitors C2 220nF Continue reading

Repeating Interval Timer Circuit

Do not use the “on-board” relay to switch mains voltage. The board’s layout does not offer sufficient isolation between the relay contacts and the low-voltage components. If you want to switch mains voltage – mount a suitably rated relay somewhere Continue reading