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simple timer needed please help

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stephen-7486

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i need some help with with a timer circuit that will hold the output high for about 30 seconds when power is applied and then go low indefinetly until it is powered down and turned on again
 

use monostable circuit .search threads in this forum you will get . Regards
 

you can use 555 in monostable mode, use the timing resistors to select 30s, when there is a signal on the input pin the output will be high for 30s and then low again until again gets a signal,
220px-555_Monostable.svg.png
you can input a pulse and the circuit would output high for 30 secs

for the resistor and capacitor values for timing u can use the program available here


go through this it will help
 

Here is one circuit.........................

You can use 4001 or 4011 cmos gates or 4049 inverters etc.
for faster output switching time add 2 additional gates serially to signal
without transistor and relay , output is over C2.
Output is logic 1 at start
Inverting output connect one inverting gate more.

**broken link removed**

Regards KAK
 

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