long time delay retriggable monostable

betwixt said:

I use a PIC10F200 for a resettable long delay timer. It is cheap, easily available and has a precision internal oscillator so no RC network is needed at all. Works from 2V up to 5V. I use them for delays of up to one month! Current consumption is only a few uA.

Brian.

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ahsan_i_h said:

When power is first applied to a PIR sensor module, its output goes high, indicating a motion is detected. After some time when adaptation with environment is complete, its output goes low and becomes ready for proper operation. So after power up CD4541B will get a positive pulse at its MASTER RESET input automatically. We dont need AUTO RESET function.



PIR sensor will automatically send the pulse.



In the previous schematic auto reset function was enabled. In CD4541B with 5v supply auto reset function is unreliable and also takes extra current.

I guess the the output of the PIR sensor module is 0-3v (TTL level). You need proper interfacing between TTL output of PIR sensor with CMOS input of CD4541B (one npn transistor, one pnp transistor and few resistors can do the job) . Besides you can also use popular CD4060B instead of CD4541B but you may need some extra components (one diode, one pnp transistor and few resistors).
74HCT series can be directly interfaced with TTL, but unfortunately 74HCT4541 does not exist, but 74HCT4060 does exist.

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why you said the PIR will send a positive to negative signal, when its power ON ?

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also from where did you get that the level of PIR module is TTL ?

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what is the problem if we interface TTL to CMOS ?

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ahsan_i_h said:

It usually does, but can not be proved from datasheet. So I suggest not to use 4541. Use CD4060B / CD74HCT4060. It does not need mandatory reset signal to start counting.



I got it from the datasheet of GH-718C
( **broken link removed** ).



if a CMOS (except TTL compatible series) IC is powered by 5v supply, then if you apply any voltage between 3.5v to 5v at any of its input then it will be considered as logic high. If you apply less than 3.5v then it may or may not be considered as logic high. TTL IC can not provide such voltage.

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if i understand well, i need to connect AR pin to VDD, and apply a low to high signal in the MR pin when i put power ON ?
that's all ?

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