Peter_n:
You can select different sleep modes, with counter enabled or disabled.
Gammon Forum : Electronics : Microprocessors : Power saving techniques for microprocessorsYou don't need a ATtiny (or Trinket), the ATmega328P as used in the Arduino Uno is just as efficient.
A complete Arduino Uno board is not very efficient, due to everything that is on the board.A good sleep mode puts the ATtiny/ATmega into sleep for a long time, even if that means that the long time is only 10ms.
Therefor using an interrupt to wakeup is no problem at all.
Everything you add to the circuit, like the 590 counter, needs current to operate. Try to do it all in the ATtiny/ATmega itself.What about the hall sensor, does it require a current to operate ?
Awesome. I'll have to try this and monitor the power usage. Obviously I'd like to get the power usage down to the point where a couple (or 4, whatever it takes) AA batteries will power it for a while (would love 3-6 months or more).
Didn't even think about the hall effect. I have a Honeywell SS494B sitting around, but it looks like it might draw 4mA, which is going to kill my battery runtime I would think. Or is that only when it's outputting a pulse, because the one sparkfun sells (Hall-Effect Sensor - US1881 (Latching) - COM-09312 - SparkFun Electronics) requires 5mA as well... I see one that draws down to 3.5mA, but all the really low current ones are all surface mount, and I'm not sure about the proximity requirement for them to get good readings off the meter.