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Electromagnet and Switch

Discussion in 'General Electronics Discussion' started by jennyanne, Oct 17, 2013.

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  1. jennyanne

    jennyanne

    5
    0
    Oct 17, 2013
    Hi

    I'm trying to combine an electromagnet with the power and a switch. Apologies, I am a complete electronics rookie.

    The electromagnet requires 24V (dc) and 0.33A which I am supplying through 16 AA batteries in series. I want to attach a switch that I have, but the switch specifies a maximum of 12V and 3A - would this work, or do I need to get a different switch?

    Thanks!

    Product links...

    Electromagnet:
    http://www.amazon.co.uk/55-6lbs-Holding-Electromagnet-Lift-Solenoid/dp/B008DB5FKS
    Switch:
    http://www.maplin.co.uk/ultra-miniature-toggle-switches-2340
     
  2. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    The batteries will be pushed to the limit and will not last long.

    The switch should be able to handle the voltage but the electromagnet will be highly inductive and will draw an arc when the switch is opened. This will rapidly destroy the contacts. The solution is to go to a fatter switch or to put a reverse diode across the magnet. This will limit the turn off voltage to 24V
     
  3. jennyanne

    jennyanne

    5
    0
    Oct 17, 2013
    Thank you very much, I thought as much, but the guy in Maplin said it would be fine. I found a switch on ebay that takes 125V and 5A, so I'm hoping that should be sufficient.

    How long would the batteries last for - I'm using the electromagnet for experiments, so I imagine it will be on intermittently for periods of around 1-2 minutes, not on constantly.

    Thanks again
     
  4. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    I am no expert in batteries, in fact I hate them.
    The batteries will have a specification of mAh. Divide this number by 330mA and this gives the number of hours under optimum conditions, you could divide this by two because you are draining the bateries very rapidly and divide by two again as the batteries, although not fully discharged, may not be able to supply enough current.

    If your experiments are looking at the magnet strength, then a mains power supply would be more consistent.
     
  5. jennyanne

    jennyanne

    5
    0
    Oct 17, 2013
    Electromagnet Circuit

    Hi

    I'm trying to get an electromagnet to work. The electromagnet requires 24V dc, 0.33A. I initially hooked it up to 16AA batteries, which whilst the magnet worked, it was definitely not achieving the 25kg pull it should do. I have since bought a 24V dc power supply, and solder-free adaptor, and hooked them all together only to have the magnet not work at all.

    Am I doing something wrong!?

    Full tech specs of the products in my circuit...
    Electromagnet:
    http://www.amazon.co.uk/55-6lbs-Holding-Electromagnet-Lift-Solenoid/dp/B008DB5FKS
    Power Supply:
    http://www.maplin.co.uk/ac-dc-fixed-voltage-switched-mode-power-supplies-48484
    Connector:
    http://www.maplin.co.uk/2.1-x-5.5mm-solderless-socket-390568

    Thank you!
     
  6. jennyanne

    jennyanne

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    0
    Oct 17, 2013
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    The AA batteries would probably not supply 330mA for very long, but assuming you connected them up correctly they should have done the job for a while.

    The power supply you link to is a 5V supply. Please read the specs of the power supply and tell us what it says.

    How are you trying to measure the "25kg pull"?

    And I just noticed you posted a similar question twice. That is really annoying because I may have just gone and researched your problem after someone else already has. Please don't do it again.
     
  8. jennyanne

    jennyanne

    5
    0
    Oct 17, 2013
    Sorry, I wanted to reply to duke in this thread, but didn't no if the subject of the thread was as relevant.

    The link I supplied for the power supply is the right one, maplin give their specs under the same product, despite a range of voltages. If you click specification, you can see all the details. I don't know what details you need, so I've just attached a screenshot.

    With regards to strengh, I have an 11kg pull magnet and that is really very strong, in comparison - the electromagnet doesn't feel anywhere near as strong despite the fact that it should be at least twice the strength.

    Thanks
     

    Attached Files:

  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    I can't comment on the difference between this and another magnet. I would suggest that if you're really interested you get manufacturers data on how these are calculated. It is possible that you are comparing apples and oranges.

    The power supply seems right. Have you got a multimeter? If you have, measure the resistance through the electromagnet (with NO power applied) and tell us what you get.
     
  10. BobK

    BobK

    7,682
    1,687
    Jan 5, 2010
    Since that magnet is intended for lifting, I will guess that the force that they state is the max that it will lift when applied to a flat magnetic surface large enough to cover the surface of the magnet.

    Bob
     
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