Timer circuit diagrams
An astable timing circuit made from the ubiquitous 741 op-amp.
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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 it. The first uses less power while the timer is running; and the second uses less power after the timer stops. Pick the one that best suits your application.
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15 seconds delayed switch-off. A good idea for bedroom lamps
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A switched timer for intervals of 5 to 30 minutes incremented in 5 minute steps.
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3V Battery powered. Beeps after a fixed minutes delay
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Beeps 7.5 seconds after a preset time Adjustable time settings: 15 s. 30 s. 1 min. 2 min. & others
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This timer was designed mainly to switch off a portable radio after some time: in this way.
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Use of the ubiquitous 555 timer in monostable mode.
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A 555 pulse generator circuit with a difference, the initial pulse is tailored by additional circuitry to match the duration of subsequent pulses
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A timer circuit with independent mark and space periods.
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