I am building a free pendulum clock, and am hoping to get pulses at
the rate of one per second from a photoelectric cell in the path of
the pendulum.
Where can I find a circuit which will count these, and give out a
signal after 30 pulses?
This would be used to drive the clock hands, and also power a magnet
to keep the pendulum swinging.
Assuming the photocell is blocked by the pendulum, and that the output
pulse is less than ten pendulum ticks, you can do something like this.
Use the quad Schmitt NAND to square up the inputs and timing for most
reliable operation:
View in a fixed-width font such as Courier.
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. Vdd
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. ---
. | / |
. | \ | PC
. | / |
. | \ |
. --- CD4093
. | __
. +----------| \
. | | o---+---------->>--+ ~ 0.7 x RT1 x CT1
. | +--|__/ | |
. [Rp] | | | -> <-
. | +----------|-------+ | ---
. | CT1 | __ | | | |
. | +--||--+-| \ | | CLOCK | |
. | | | o-+ | -- ---
. +----[RT1]--+-[220K]-|__/ |
. | |
. GND |
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. +------------------------+
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. | +---4017---+ +---4017---+
. +->>--|CK Q0| +--------------|CK Q0|
. | | | | |
. | . | | | Q1|
. | . | | | . |
. | . | | | Q2|
. | | | | |
. +--|MR Q9| | +--|MR Q3|--+
. | |__ | | | |__ | |
. +--|EN | | +--------|--|EN | |
. | | | | | | | | |
. | | CARRY | | | | | CARRY | |
. | +----------+ | | | +----------+ |
. | | | | | |
. | +--------+ | | |
. | | | |
. | | | |
. GND --------+--------------------+ | |
. | |
. +------[10K]-------------------------------------+
. | |
. | __ CD4093 |
. +--| \ |
. | | o---+ | ---------
. Vdd--+-----|__/ | | | |
. | | === | | |
. | | +|CT2 | --- ---
. | | 1N4148 | |
. | +--|<|-----|--------------------+----> PULSE OUT
. | | __ |
. +-----[RT2]---+--[220K]-| \ |
. | | o------+
. +-----------------------|__/
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