15 Apr
2012
15 Apr
'12
4:58 p.m.
On 15/04/2012 21:15, Mouse wrote:
To toot my own horn a little in this respect, I
recently had occasion
to build something that could switch power to a camera on for something
like ten seconds every two minutes [...]
My first reaction was a 555 with a few external
discretes to convert the
555's voltage-level output into a current switch. Built it, and it
worked. (I used bipolar transistors for the switching because that's
what I know; a FET would maybe have made more sense as the switch.)
Then someone mentioned doing it with an Arduino or something of that
ilk. But, on investigating, the uP solution would have drawn enough
power to significantly impair battery life as compared to my circuit.
Apparently my first reaction was the righter answer. :)
I wanted a slave flash trigger which would be compact, and smart enough
to work for ordinary flashes (from an SLR with a conventional flashgun)
or for a compact (which has a pre-flash that can't be disabled). My
design used a small PIC, a phototransistor, a few resistors, a small
thyristor, and a CR2032 lithium cell. It's turned on and off by a
momentary pushbutton, or can be made to go to sleep or wake up by the
PIC's internal timer. It runs for months on a single CR2032, because
the current draw is very low. So a properly-designed uP solution
needn't be a problem.
--
Pete Peter Turnbull
Network Manager
University of York