Solenoid Construction

Some of 'em do!!!

Latching solenoid...

Short pulse of current in one direction pulls it in (and it stays in).

Short pulls in opposite diection pushes it out (and it stays out).

Very economic in power terms on battery operated equipment!

Del

The only latching electro magnets I have seen were mechanical, this is a new one to me which is interesting.

I suppose it has to be a dc variant as ac variants will never do this. They just build up a field which attracts the soft metal core, always. Just like any magnet will always stick to metal no matter which way you place it on the metal. It will only repel something of the same polarity which means you need 2 magnets.

I have just solved my querie just by writing it down while answering. It has to be a dc coil and the anvil is permanently magnetised. The coil's direction is changed by polarity thus rejecting the core or attracting it the other way.

That is clever Del, thank you.

Hi Case491, that's also why those cranes with the electromagnets to pick up cars and other junk, use permanent magnets, with a coil (solenoid) wound around it, so that if ever the power failled the magnet would remain activated and wouldn't drop its load!!

The only way to drop its load, or release the magnetic field is to energise the solenoid to oppose the magnetic field of the permanent magnet.

John.

Solenoid and motors are different in operations as you see , there is no magnetic field inside solenoid only flow of current induce magnetism to attract metal , if there had been suppose a permenant magnet with polarity in perticular direction along the solonoid it would have that reversal effect , that may explain you the working of permanant magnet DC motor and its reversal with change of polarity