Electromagnets on a timer?

[Surprise]

Hello, this looks to be a great place to get some information on a project i want to built.
So here is the idea, i just dont know which way to take it, what the best components for the circuit are,etc. Any help would be appreciated.

I would like to be able to have two DC Electromagnets and be able to vary the ampere through them in as wide a range as possible.
For this purpose a lab/school benchtop powersupply source seems to be the best choice, right?
I would also like them to be on a variable timer, so that one is one while the other electromagnet is off, and then after a particular amount of time, i would like to turn the first magnet off, and the second one on. This particular amount of time should be adjustable from miliseconds (or smaller if possible) to a couple of seconds.
Will a 555 deliver this adjustability?
I really do not know much about timers,etc, so any help would be great. Schematics of a possible circuit would be cool.

Thank you all in advance,
Surprise

 

[blueroomelectronics]

What time interval?

 

[Surprise]

In the best case scenario: A adjustable time interval, one that allows switching of electromagnets like 50 times a seconds or even more often, but it should also be able to have longer time intervals, like a couple of seconds even.
Thank you,
Surprise

 

[blueroomelectronics]

At 50Hz your magnet will probably simply be on. What are you building?

 

[Surprise]

So you reckon that at 50Hz the Coil will simply stay magnetized? so what do you reckon is the minimum amount of 'off time' for the coil to demagnetizise?
I am hoping to build an electromagnetic shaker to 'shake' (move forwards and backwards) small metallic objects using two electromagnets and leaving one on while the other is off, and then switching them.
Is there a better way to 'shake' small metallic objects using magnetism?
What is the best way to achieve a variable time switch that can switch on/off the two electromagnets as described above?
Thank you

 

[blueroomelectronics]

It depends on the coil. What are you trying to build?

 

[Pommie]

If you use the right materials for the magnetic core then you can switch it as fast as you like. Aquarium pumps use the 50Hz mains to move a permanent magnet on a diaphram to pump air.

As Bill asked, what are you trying to build.

Mike.

 

[john1]

Hello Surprise,

Read your post about making a shaking device.

I am hoping to build an electromagnetic shaker to 'shake' (move forwards and backwards) small metallic objects using two electromagnets and leaving one on while the other is off, and then switching them.

Well, as you may know, out of all the many different metals that are around (a lot), magnets will only work with iron. (and iron-based)

This can be useful for separating out bits of ferrous metals from non-ferrous, but it might not be of any help to you.

Many small metal objects are not iron. Most are not. Depends where you look of course. A bunch of keys, keys are unlikely to be magnetic, but the key ring would almost certainly be magnetic.

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Unless you are referring to small objects that you know to be magnetic.
Even so, i think a motor driven shaker would be better for most purposes.

If it is necessary to shake these small objects, and for some reason it is impractical to shake the container, then i would consider a large motor driven permanent magnet on a shaft, with pole-pieces to the container.
You can get some very strong permanent magnets these days, and making something like that would be easy.

Best of luck with it, John

 

[blueroomelectronics]

Why would the OP want to do such a thing? What purpose would it serve?

 

[john1]

Hi BlueRoomElectronics,

An interesting comment.
Why would the OP want to do such a thing? What purpose would it serve?

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The OP should find out if the small metallic objects are iron (based).
Because it wont work if they're not.

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A motor driven shaker would be much simpler to construct, especially if the OP has limited electronics experience.

**********

As to mounting a strong magnet on a shaft to revolve it...
Getting semiconductors to generate magnetism anywhere near that of decent ready made permanent magnets, and switch it on and off at any reasonable speed would be quite a task. Some of these permanent magnets are so strong, that you have to be very careful not to trap your fingers, as that could cause a bad injury.
And a permanent magnet would not need to have a current source.

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Often a mechanical solution is easier and quicker to construct, and often easier to understand for a lot of constructors.

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Unless of course this is some sort of test, or school project.
But it seemed to me like the OP had a real use for such a unit.

Regards, John

 

[Surprise]

Yes, i do know the small objects to be magnetic, and yes, the container can not be shook. (I want it to be a magnetic shaker) I had taught about putting permanent magnets on a shaft and moving them towards and away from the small objects. I was just hoping that an electronic solution, rather than a mechanical solution would be the neater solution and provide more accuracy and variability, but i will have a rethink and consider a mechanical solution (perhaps a permanent magnet on a stroke-action motor or even a solenoid, or the revolving method suggested by John1, sounds very very straight forward), unless someone can come up with the idea for a better solution.

Thank you

 

[john1]

Hi Surprise,

Please don't let me put you off making an electronic unit if that is what you want to do.
The timer/timing part of the circuit would not be a problem, i feel that the output stage and power supply stage would be the difficult part.

You don't mention the size of the container, this is very relevant because the magnetism drops away very sharply with distance from the magnet.

Are the little objects immersed in fluid?
because moving/vibrating them is probably easier if they are.

If they are very small, then they might respond to the mains frequency, but they would have to be pretty small.
If so, that might simplify your arrangements a lot.

Also the little objects might pick up residue magnetism, and some of them might end up slightly magnetic.
You would have to check in case that became a problem.

*************

I have seen little ultrasonic units that jewellers use sometimes to clean fiddly little items.
Have you considered that sort of thing ?

Regards, John

 

[blueroomelectronics]

I'm simply curious as to the purpose of making such a device. It's a very inefficient way of transferring magnetic energy. Is it to recharge a shaker flashlight?