Photography by Larry Cotton


Transplant a heartbeat from cheap alarm clocks.

By Larry Cotton

Some projects need a nice, steady, low-voltage pulse at a constant rate. This is relatively easy to do with the ubiquitous 555 IC, but what’s not so easy is keeping a 555-based circuit accurate to within a few seconds a month. For that, you’re better off just gutting a cheap travel clock. This will give you an easy module that generates ultraaccurate pulses at 1Hz — something which, in my opinion, is more valuable than telling time.

Not just any clock will do, however: it should run on one battery (usually AA size) and have hands, not ...

Get Make: Technology on Your Time Volume 09 now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.