I'm an avid DIYer, I don't know anything about circuits, meters, mathmatical equations etc. I have created a secret storage compartment so the door has no visible hinges, handles or locks, It's made of wood and weighs around 10 kg, it's held closed with medium strength magnets. I'm looking at using a push solenoid with a spring to return the pin back to starting position connectted to a doorbell type button via the main lighting circuit using 1.5 cable. 2 problems. Firstly can this be done, do I have to add a transformer into the mix,if so how? Secondly how will I know if the power of the solenoid will be able to detach the door from the magnets to open? Only place that sells solenoids in lamens terms is Amazon so this is where I'll be purchasing it from.
Electronic – Power supply for a solenoid to open a secret compartment
mainspowersolenoid
Best Answer
I think you may be using the wrong mechanism for the lock. Maglocks (magnetic locks) are widely used for this type of application in building security. They come in two modes: release when power off (suitable for most applications) and require power to release (prisons, etc.).
Figure 1. Maglock with magnetic poles exposed and keeper.
It seems to me that the three poles are arranged as south-north-south (or vice-versa) and that the coil is wound, pushed into the black slots and potted in position. Once the (electro) magnet hits the keeper the magnetic circuit is closed. As anyone who has played with a horseshoe magnet will know, opening the closed loop is very difficult.
Figure 2. Cross-sectional view.
Here we can see that with the lock open the exposed faces are poles of the electro-magnet. Note also that the magnetic path is twice as wide in the centre pole as on the upper and lower poles so that flux density is fairly constant. Once the lock closes the flux forms a loop through the iron core.
The "normally locked" version requires power to unlock. The coils are typically 12 or 24 V so that the controller can run with a small lead-acid battery backup. You would need to check the datasheets to learn how much current they consume and purchase a suitable power supply.
Figure 3. A compact cylindrical magnetic lock.
The locking force will probably be rated in newtons (N). You can convert this to kg-force by dividing by 10. (Actually 9.81 m/s², the acceleration due to gravity but 10 is close enough.) Remember that you want the "energise to release" type. These are not the usual types sold.