[time-nuts] low power divide by 5

[jimlux]

On 7/2/20 2:13 PM, Peter McCollum wrote:
> Another way to achieve divide-by-N is with a non-retriggerable one-shot,
> adjusted to the appropriate time value.
> Back in the 40's/50's, the common tube circuit was called a Phantastron
> (really, look it up!).
> Phantastron dividers were used in several of the early HP counters (i.e.
> HP524B), because you could achieve (for example) a decade divider with a
> single tube, whereas a 'binary' solution requires 4 tubes (like in the HP
> AC-4A decades).
> 
> If a 50% duty cycle is needed, then do a divide by N/2 with a Phantastron,
> then a single flip-flop gives you 'N' with a 50% duty.
> 
> Note that the Phantastron type divider only works if the input freq is
> known and fixed, because the one-shot delay has to be adjusted to a
> specific value.
> 
> Pete
> 

And you can be clever if you can trigger on both rising and falling 
edges, so you get basically a x2 and a divide by 5 in the same circuit, 
followed by the divide by 2 to make the duty cycle 50/50.