Parameters for small electromagnet

[Bretina]

I've been searching unsuccessfully for an electromagnet for my application and unless anyone can provide a source lead, I'll try to make one myself. I need some guidance for the parameters I need to say within so I don't waste time.

It needs to be small, say no more than 1" long by 3/8" dia., as powerful as possible given it needs to function from no more than a small 12v power source battery - but lower voltage is better and one which can be purchased at a local store such as CVS, Radio Shack, Walgreens etc. The travel of the rod should be around 1/2" if possible. That should do it.

1- Can any other shape be used other than cylindrical, say more flat or rectangular?
2- Is fine wire wound around better than thicker wire?
3- Would any wire material other than copper be feasible - how much of a drop in power or reaction time would using another material provide?

Thanks

Bretina
FL, USA

 

[waross]

You may have better luck asking in the Magnetic engineering Forum. Also a little research on basic electromagnetism may also be a good idea.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[iceworm]

The travel of the rod should be around 1/2" if possible.

Are you trying to build a solenoid with a moving armature, or just a magnet?

ice

Harmless flakes working together can unleash an avalanche of destruction

 

[iceworm]

You may have better luck asking in the Magnetic engineering Forum

Where is the "Magnetic Engineering Forum' I am not seeing it.

I have an interest in non-ferrous magnetic application. Be interesting to see what discussions are available

ice

Harmless flakes working together can unleash an avalanche of destruction

 

[waross]

Magnetic engineering Forum forum340

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[iceworm]

Thank you - I would never have found that without help.

ice

Harmless flakes working together can unleash an avalanche of destruction

 

[Bretina]

Thanks for the replies.

It would be a solenoid with a moving armature. The "rod" in my question is the armature.

It being a device with moving parts, I posted the question here. Is it more appropriate to be in the magnetic forum?

Bretina
FL, USA

 

[israelkk]

What is the starting force that the solenoid needs to overcome from the 1/2" distance?
How the force is changes (rises?) with the 1/2" travel of the plunger?
Is there a requirement for the electrical and mechanical time from "ON" pulse till the plunger moves the 1/2"?
How frequent it will need to be operated (frequency, Duty Cycle)?
How the plunger is supposed to return to its initial position when the current is OFF?
What else is connected to the plunger and how much it weighs (inertia)?
Maximum current allowed?

 

[OperaHouse]

To get the most out of a small package you will need electronic control for the drive. Otherwise you will overheat or have to make a larger assembly. Hold in current is far less than one quarter of pull in. There are driver chips that will PWM the current after pull in or you can use a micro. I drive 6V coils with over 60V for speed and less heat.

 

[waross]

It may be a lot easier to check the catalogues and just buy a solenoid designed and built by experts in the field.
Before you set out to redesign the wheel, remember that for all but the most exotic applications it will be difficult to best a group with many cumulative years of experience and proven results working to the goals of efficiency, competitive cost and performance.
Given the often very large ratio between the pull in current and the holding current, many commercial solenoids will withstand pull in voltages and currents far in excess of their continuous ratings.
One source:

http://download.transmotec.com/eng/solenoids/tubular/Transmotec-Solenoids-Tubular-eng.A.pdf

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Bretina]

Those are excellent suggestions and questions. The transmotec sample should be a good starting point to test with. Thanks.

I've been somewhat general because I know the device needs to be tested and I don't want to take more of your time than is necessary until I know specifically what's possible, although I do know some general size and power limitations for now, as described.

This solenoid will have a very short cycle time - fraction of a second for it to activate and return to original position.

The extended position (I'm still not sure if pulling or pushing will be best but either would involve springs to return it to it's original position) needs to be firm as it will be pushing a small braking mechanism which will engage for just an instant. Exactly how long the "instant" is I don't know yet. I also don't yet know what the forces the brake needs to stop are yet. Basically, this brake is intended to work something like throwing a "wrench into the gears" effect but with a very fast reaction time. The brake takes the load and the solenoid just places it into position for an instant.

The duty cycle probably won't be more than 100 within a 3 hour period each day.

If you're suggesting a 6v power source can be boosted to 60v, this is very interesting as it may add speed and holding strength. A capacitor may add some instantaneous boost although might require an unacceptable delay between cycles?

Overall, it sounds as this will work. I just need to get some parts and start testing to better define things.

Bretina
FL, USA