# Need help

#### Gone50to

Joined Aug 29, 2008
3
anyone know where to buy a small electromagnet that switches its polarity on and off?

#### mik3

Joined Feb 4, 2008
4,843
anyone know where to buy a small electromagnet that switches its polarity on and off?
Can you give more information and what exactly do you want

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#### Gone50to

Joined Aug 29, 2008
3
I need a small electromagnet in a cylinder shape for contact. I need the polarity to be switched easily but with strong fields. Is there any place that sells them or do i have to make one. I need there to be a switch somewhere to switch the polarity very fast back and forth. Is there any way to make a mini spring contact where when the piece of metal is pushed down onto the other piece it can switch polarity.

#### SgtWookie

Joined Jul 17, 2007
22,210
I need a small electromagnet in a cylinder shape for contact.
Do you have particular dimensions in mind? Small might be 2" long, 1" diameter. It could also be 1" long, 1/2" diameter. Or larger, or smaller. It's a relative thing.

I need the polarity to be switched easily but with strong fields.
Switching polarities is easily done with a DPDT (double pole double throw) switch or relay.

Is there any place that sells them or do i have to make one.
There are a number of places that sell electromagnets. Alternatively, you could buy a solenoid of suitable voltage.

[eta] Try this Google search; I received nearly a million hits:

I need there to be a switch somewhere to switch the polarity very fast back and forth.
How fast is very fast? 100mS (1/10 second)?

Is there any way to make a mini spring contact where when the piece of metal is pushed down onto the other piece it can switch polarity.
Well, you can get microswitches that are controlled by a lever; the microswitch contacts could power the coil of a DPDT relay.

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#### Gone50to

Joined Aug 29, 2008
3
could somebody draw me a diagram and parts list? 2" long 3inch diameter. Where do buy a double pole trhow switch etc. I need the small electromegnet,switch polarity,onpoff power and polarity switch buttin thanks!

#### beenthere

Joined Apr 20, 2004
15,819
If all the solenoid does is operate a switch, then a relay will do that more easily.

#### SgtWookie

Joined Jul 17, 2007
22,210
could somebody draw me a diagram and parts list? 2" long 3inch diameter. Where do buy a double pole trhow switch etc. I need the small electromegnet,switch polarity,onpoff power and polarity switch buttin thanks!
There is an electromagnet of those approximate dimensions on this page:
http://www.apwcoinc.com/e-magnet.php
EM300, 3" diameter 1.5" long, 300 to 400lb holding force.
In DC, they're available for 3V, 4V, 6V, 12V, 24V, 90V, 110V, 220V.
DC power rating is 15 Watts.
Prices range from roughly $90 to$140, depending on options.

Did you have a suppy voltage in mind?

Is this in the price range that you were considering?

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