locking a box

I am currently working on a box, which is unlocked using an Arduino. I have finished all the programming and the missing part is the locking mechanism. Now there are two option I have found so far:

  • using a servo
  • using a solenoid

There are a few important factors for me:

  • it needs to function in a dirty environment, rain etc, without failure
  • it needs to withstand being heavily shaken and dropped
  • it needs to be small since everything needs to fit inside the lid of the box

solenoids seem to be the logical choice however I have looked into it and the problem i have found is, that it is difficult to keep them in the open position for long and you have to be careful about voltage spikes once the power fades. My problem with servos on the other hand is that there are the added parts and hence points of failure. Most notably because the rotary motion needs to be converted to a linear one.

I am basically looking for something like an linear actuator which does not need additional control boards or an additional power supply / higher voltage etc. Maybe I am missing something obvious and someone has an idea

best regards

A Selenod with a magnet willo work in both positions, open and closed.

blubble:
I am basically looking for something like an linear actuator which does not need additional control boards or an additional power supply / higher voltage etc.

Do you envision driving this solely with the Arduino?

Ideally yes. Everything else connected to it works at 3.3V

blubble:
Ideally yes. Everything else connected to it works at 3.3V

Here's a dose of realism, the absolute maximum current on any Arduino I/O pin is 40ma. If you want the chip to run a long time you'll keep well below that, 20ma is more common. And, the maximum for the chip is 200ma. The ATM328 is not an I/O driver. Output transistors are advisable if for nothing else than isolating the controller from the large currents generated when the coil shuts off.

There are 5v, low current motors out there but, naturally, they're small and not very powerful.

Maybe a latching solenoid or a magnetic lock would get you there.

How do you open it when the battery is dead ?