Dividing circuit?

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.

. . . . . Vdd . | . --- . | / | . | \\ | PC . | / | . | \\ | . --- CD4093 . | __ . +----------| \\ . | | o---+---------->>--+ ~ 0.7 x RT1 x CT1 . | +--|__/ | | . [Rp] | | | -> >--|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------+ . +-----------------------|__/ . . . .

If the PULSE OUT is long, then you may need to add a fast recovery diode to the output monostable: View in a fixed-width font such as Courier.

. . . . . Vdd . | . --- . | / | . | \\ | PC . | / | . | \\ | . --- CD4093 . | __ . +----------| \\ . | | o---+---------->>--+ ~ 0.7 x RT1 x CT1 . | +--|__/ | | . [Rp] | | | -> >--|CK Q0| +--------------|CK Q0| . | | | | | . | . | | | Q1| . | . | | | . | . | . | | | Q2| . | | | | | . +--|MR Q9| | +--|MR Q3|--+ . | |__ | | | |__ | | . +--|EN | | +--------|--|EN | | . | | | | | | | | | . | | CARRY | | | | | CARRY | | . | +----------+ | | | +----------+ | . | | | | | | . | +--------+ | | | . | | | | . | | | | . GND --------+--------------------+ | | . | | . +------[10K]-------------------------------------+ . | | . | __ CD4093 | . +--| \\ | . | | o---+ | --------- . Vdd--+-----|__/ | | | | . | | === | | | . | | +|CT2 | --- --- . | | 1N4148 | | . | +--| PULSE OUT . | | | . | 1N4148 | | . +-----|

I just noticed that Mr Craig posted this twice; once to sci.electronics.design and once to alt.horology. If I had been aware of this I would not have replied to the post in alt.horology.

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. Thanks for any help, John