Hi... I remember having seen an interesting analog counter/frequency divider using charge pumps and unijunction transistors in a watchmaker's mechanical watch adjusting machine. ( i don't remember the machine's name, but it is used to adjust the oscillator's (balance wheel/hairspring) frequency.
The interesting part was that the unijunctions worked in a charge pump fashion rather than an RC time constant fashion. This way, at least theorically (i never tried it), the counter could be used with a variable frequency source. The principle is simple: The unijunction transistor is used in it's traditional relaxation oscillator circuit, except that there's no pullup resistor between the unijunction's emitter and supply line. The Emitter-ground capacitor is charged by another (smaller) capacitor through a series diode an a calibrated voltage pulse. This way, at each input pulse, the capacitor is charged with a fixed (predetermined) voltage increment. After 'n' pulses, when the emitter reaches the discharge voltage, the UJT fires and sends an output pulse. (If one watches the emitter voltage with a scope, he will see a staircase waveform). The interesting part is that the voltage increment remains fixed, regardless of the pulse's duration or frequency (up to a certain extent...). I know, it's hard to describe the circuit with words, but if i find the schematic, i'll find a way to send it here. Have a good day! Normand Martel Montreal, Qc. Canada __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
