Electromagnets - McMaster

[Sh1ine]

Has anyone ever used a Electromagnet from McMaster? We were going to, and then I noticed that you need a power supply to go along with it, however the power supply is used to convert AC to DC and of course we run DC.

I was originally planning on using a Spike to control a 5698K311 which is a 12 v 8 watt Electromagnet with a 100lbs pull force.

http://www.mcmaster.com/#electromagnets/=ayig32

Thanks.

[MrForbes]

McM sells parts mostly for industrial applications...so yeah, they'd say you need to use a power supply to get DC, assuming you're powering it from awall outlet. Since you're building a robot that runs on DC, you need to get DC from your robot power system, and a Spike seems to me the obvious way to do it. You could even use it to reverse the current to release the magnet (as the description on the McM page about power supplies implies you must).

I haven't used them, but please let us know how it works out!

[Sh1ine]

Originally Posted by squirrel

McM sells parts mostly for industrial applications...so yeah, they'd say you need to use a power supply to get DC, assuming you're powering it from awall outlet. Since you're building a robot that runs on DC, you need to get DC from your robot power system, and a Spike seems to me the obvious way to do it. You could even use it to reverse the current to release the magnet (as the description on the McM page about power supplies implies you must).

I haven't used them, but please let us know how it works out!

I know that the Nerds are going to hate me for this, but I think you really need to consider moving to the Albany area. We need you here Jim!

Forgive my ignorance, but do you think I will need to build a custom PCB to reduce the amperage to the system?

[Chris is me]

Originally Posted by Sh1ine

I know that the Nerds are going to hate me for this, but I think you really need to consider moving to the Albany area. We need you here Jim!

We could take the rest of their team too!

I'm not familiar enough with the manual but I would make sure electromagnets are explicitly permitted - I believe in past years they could be considered electric solenoids which would make their use a little less than legal.

[MrForbes]

Originally Posted by Sh1ine

Forgive my ignorance, but do you think I will need to build a custom PCB to reduce the amperage to the system?

I'm not moving to NY, this sham of cold weather we've been having here is bad enough

The magnet will act as it's own current limiter....whatever the watt rating is, divide that by the voltage rating and you should get an approximation of the current it will draw. Make sure it's under 20 amps to be able to use a Spike...or whatever the maximum current rating of a Spike circuit is allowed to be (I just pulled the 20A number from thin air, you need to study the rules)

[Jon Stratis]

Be very careful on how to use your electromagnet.

<R46> Items specifically PROHIBITED from use on the ROBOT include:
A. Electric motors and/or servos different from, or in addition to, those listed in the 2011 KOP Checklist, with the exception of those specifically permitted by Rule <R45>.
Electric solenoid actuators (note: electric solenoid actuators are NOT the same as pneumatic solenoid valves – the latter are permitted, the former are not).

In the past*, we've seen the GDC rule that an electromagnet could be considered a solenoid and thus be prohibited depending on its use. Specifically, if you used the electromagnet to create any motion (for example, turn it on and it pulls a lever from one location to another), it would be illegal. An electromagnet that was utilized specifically for the purposes of attachment would be permitted (using the same example, a motor moves the lever into the desired position, then the electromagnet activates to hold it in position).


I would highly recommend asking the GDC about electromagnet applications with regards to the above rule.


*Please note that past year GDC rulings don't necessarily apply to this year... but they can give a very good indication as to how the GDC will rule with regards to certain applications and similar rules.

[Chris is me]

Knowing (vaguely) the possible application of the electromagnet - I think a spring loaded locking pin would work better. Think like the little nubby clips on chair legs, or those things that Razor scooter handlebars are held in with.

[MrForbes]

In the past, using electromagnets to release things has been OK, but using them to move things has not been OK.

As mentioned, study the rules, and ask Q&A if there is any doubt. Be sure to describe exactly what you intend to do with the electromagnet.

[Hugh Meyer]

We tried to use one last year to hold and release our kicker. The problem was the release time. When the power is removed from these they hold on for about a second or so before the field decays enough to let go. If you have a diode across it to kill the back emf it takes even more time. They are heavy as well.

-Hugh

[Stepol]

We use electromagnets on Longarm Quilting Machines for channel lock. The magnets are spring-loaded so that the springs are compressed when the magnet is engaged and then the springs cause the magnet to release as soon as the power is removed. We are considering using this type of magnet.