The electronic circuit provides a visual time 9 second delay using ten
LED before control by closing a 12 Vdc relay. That the reset switch has
closed, IC 4017 decade counter will be reset to zero count which
illuminates the LED driven from pin 3. IC 555 timer output at pin 3 will
be high and the voltage at pins 6 and 2 of the timer will be a little
less than the lower trigger point, or about 3 Vdc.
9 Sec Timer with LED Indication and Control Relay Circuit Schematic
That time the switch is opened, the transistor in parallel with the
timing capacitor (22uF) is shut off allowing the capacitor to begin
charging and the IC 555 timer circuit to produce an approximate one
second clock signal to the decade counter. The counter advances on each
positive going change at pin 14 and is enabled with pin 13 terminated
low. When the 9th count is reached, pin 11 and 13 will be high, stopping
the counter and energizing the relay. Longer delay times can be
obtained with most capacitor or most resistor at pins 2 and 6 of the IC
555 timer.
9 Sec Timer with LED Indication and Control Relay Circuit Schematic
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