Electronics > Beginners
How does an electronic safe use a 9v battery to power a solenoid?
IDEngineer:
I've also seen battery powered applications like this use a motor or other rotary element to move the physical piece. Movement is slower but still well within human satisfaction. The benefits include lower current to actuate and potentially zero current when not changing.
james_s:
Yes that works too, although I suspect a motor would not consume less power in this case, by design it's only going to give you a few seconds to open the thing after entering a valid combination. A motor would just have to crank it one way, stop, then crank it the other way a few seconds later. I doubt that would consume less power than holding in a small solenoid for the same period. It's also likely to be more mechanically complex and failure prone.
IDEngineer:
I was thinking of rotating the motor ~180 degrees, to swing an arm that selectively locks the mechanism. That would take very little power and only during transitions.
Brumby:
That would depend on the motor, the arm and the lock structure. A single 180ยบ movement would require a certain amount of current, whereas a much less powerful motor running through a reduction gear set could achieve the objective with a significantly lower peak current requirement. Yes, it would need to run for longer, but it's the total energy use that is important here.
I think I'd prefer to stick to the solenoid - especially since that mechanical structure is already in place and functional.
IDEngineer:
I was just brainstorming... since you're retrofitting I agree, stick with what you've got.
Another option for the motor approach would be a small stepper. Could be very low power, has some position retention with zero power.
Lots of options, especially with a blank slate.
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