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I am designing a device in which I want to lock each drawer until it's time to open them. Let's say that there are 4 compartments in the device. Each compartment needs to be programmed to open at a pre-programed time. For example, at T1 time, compartment 1 opens. Then at T1 time, none of the other compartments should be able to open even if pulled by the user. The same should be true for all the other compartments.

My earlier approach included using a solenoidal actuator for this. So, the holding current of the actuator would keep it magnetised and hence latched. And whichever compartment needs to be opened, that actuator is set to low.

However, I am unable to find any solenoidal actuator below 1Amp rating.

I would like to hear if you have any other solutions for this sort of locking mechanism.

Thanks in advance.

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  • $\begingroup$ Instead of a solenoid that needs current continuously, what about a small motor that drives a gear and worm with a threaded rod that extends / retracts to lock / unlock each drawer as required? $\endgroup$
    – Solar Mike
    Commented May 28, 2017 at 6:01
  • $\begingroup$ If this is used, then I would have to time the retraction of the drawer as well right? I mean, it won't be a push and close the drawer mechanism anymore. And if a user is interacting with it, then the user will have to be aware of how long the drawer will be open for them to retrieve the contents from it. $\endgroup$
    – S_Learner
    Commented May 28, 2017 at 6:14
  • $\begingroup$ put contacts so the system will only operate when the drawer is closed. The the drawer can be open for as long as. Also, you can operate "close" cycles as often as you wish so any drawer that is now closed gets locked or use the closing contacts to trigger the close cycle. $\endgroup$
    – Solar Mike
    Commented May 28, 2017 at 6:16
  • $\begingroup$ Re-reading your comment - what I suggested does not open or close the drawer - it is just to allow the drawer to be opened. If you make a mechanism that will close the drawer you will need to provide a force limit system otherwise you have created a "finger remover" .... $\endgroup$
    – Solar Mike
    Commented May 28, 2017 at 6:29
  • $\begingroup$ Finger remover? How so? $\endgroup$
    – S_Learner
    Commented May 28, 2017 at 6:40

1 Answer 1

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Try a bi-stable lock/unlock mechanism per drawer. A solenoid or perhaps two flip the state of the lock. No power is needed to stay in any one state, only to flip states.

Since the solenoids only need to be run for a short time, like maybe 50 ms, the large current spike can be supplied locally by a capacitor. That capacitor can then charge up more slowly between actuations.

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  • $\begingroup$ But in this model also, I would have to use 2 solenoids per door right? Is there no way to limit the number of components and the power consumption at the same time? $\endgroup$
    – S_Learner
    Commented May 28, 2017 at 17:38
  • $\begingroup$ This could work. However, it should be noted that billions of car door lock actuators use small electric motors and a gear train. $\endgroup$
    – Spencer Joplin
    Commented May 28, 2017 at 22:44

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