Mechanism to oscillate a needle like object in vertical motion

Question

I need to pop out a needle like object(toothpick,matchstick,etc) from a hole in a surface and push it back in automatically.I need to make a array of such needles in which each needle's position can be controlled individually.The objects aren't supposed to be oscillated continuously, instead they are to be locked in one of the two positions-either above the surface or inside it. I am trying to search a mechanism to achieve this.This can be easily done with a simple DC servo motor, but the problem is I have to do this in very limited space-about 6 such objects in base area of 3 cm x 3 cm.Moreover the power source would be DC +5 V

So far I have thought of creating small electromagnets with springs,but still not sure about it.Any inputs will be appreciated.

Answer 1

You might consider a Bistable Solenoid. This is a solenoid where the plunger locks into position at either end of its stroke, so that the current only needs to flow to change the state of the solenoid. Usually the locking mechanism is a simple magnet, so the electric field of the solenoid can overcome it to cause the plunger to move.

The diagram shows a cross section through the design. The solenoid is at the bottom. Run the current one way, and the plunger magnet is pushed to the top, where it sticks to the steel tube. Stop the current, and the plunger stays in position. Reverse the current, and the plunger will be pulled back down.