I am working on a project, in which I have a small box, in which I need it to be locked from the inside. It will have a panel on the front to enter in a code to open it. It needs to be very small, with a small battery.

I was thinking of using a solenoid to have the pin extend, and go through a circular latch to keep it shut. I have seen that even the small solenoids draw a lot of current and am unsure if there is a better way.

I have also seen just linear actuators, driven by a servo/motor, but they seem quite weak for this.

It doesn't need to be really secure, it just needs to keep it shut and prevent easy opening of it. I also would like it to be powered by a single LiPo cell, as that makes it easier for the charging circuitry.


  • \$\begingroup\$ probably a rotary driven lock that requires little power to move and a strong retainer either timed or limit switch sensed with no power after or a mechanical lock and electromagnetic unlatch is simpler. But that is a mechanical design. \$\endgroup\$ – Sunnyskyguy EE75 Aug 28 '17 at 23:01
  • \$\begingroup\$ If the latch is driven to the locked position by a spring, and the solenoid is only energized for a few seconds to unlock the latch, power consumption should not be a significant consideration. \$\endgroup\$ – Peter Bennett Aug 29 '17 at 0:37

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