powering a rapid on/off relay for electromagnets?

Discussion in 'General Electronics Chat' started by kiel long, Apr 11, 2009.

  1. kiel long

    Thread Starter New Member

    Apr 11, 2009
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    hi everyone, probably a newbie question..but im new to electronics.

    basically, im doing an art project for university and this will require that i attract ferro fluid (or some other magnetic stuff...) at a very rapid rate (to create a wave like pattern).

    i have (or can get hold of) a controller that will switch the relays at a very quick rate (upwards of cycles of 10 hz which is all i need.) i also have the electro magnets (thanks ebay :) ) and i can get the relays easily enough.. but......

    what can i use as the "large" power for the magnets (there is four of them)?
    if it is being turned on and off at 10hz cycles wont it trip all the fuses in the house?? and how can i prevent this??? is there some kind of a transformer power suply that can deal with it??
    it wont be a constant on off @ 10hz either sometimes it will be slower and longer holds and other times it will be short little holds...
    the magnets are http://www.magnetschultz.co.uk/docs/Electromagnets/GMH GZZ.pdf ( the 030 24v model) i was told that 3.6w is what they need???

    any help to this would be much apreciated... hope i explained it well enough for you all to understand..
    ps im in the uk if this changes anything power wise. :D
    thanks.
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    In the datasheet there are different sizes and voltages.
    What size and voltage do you intend to use?

    Greetings,
    Bertus
     
  3. kiel long

    Thread Starter New Member

    Apr 11, 2009
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    hi there, well on the sheet they are the 030
    it says on the side of the magnet gmhx030x00d02, =24v 100%ed
    so im guessing that it is 24v dc.
     
  4. bertus

    Administrator

    Apr 5, 2008
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  5. SgtWookie

    Expert

    Jul 17, 2007
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    Use LM/SE/NE555 timers along with suitable power MOSFETs to sink current from the electromagnets. Make sure you use diodes connected in reverse (cathode towards +V) across each electromagnet's windings; otherwise when the MOSFETs are turned off, the reverse-EMF across the windings could destroy the MOSFET.

    Note that 555's are generally limited to a maximum of 16v for the supply.

    Bill Marsden's PWM circuit on that page would be a good one to use. You'll also need a resistor to connect the output of the 555 to the MOSFET's gate; somewhere between 39 and 62 Ohms would be appropriate.
     
  6. kiel long

    Thread Starter New Member

    Apr 11, 2009
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    is the 555 generating timing??
    i do not need something to control the timing, this i can do with the relays on/off controlled via pc.
    its just the power to the magnets need to be able to switch on and off without causing circuits in my home to trip.
    i did just think what about a hifi amplifier?? or atleast something simular ? will that work? something like this? http://www.maplin.co.uk/Module.aspx?ModuleNo=10502 ???
    sorry for being a noob with this! :D
     
  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    A Hifi amplfier is for amplifing sound (20 Hz - 20 kHz).
    Most times amplifiers are AC coupled. A DC pulse will be blocked.
    What output of your PC do you intend to use to drive the coils?

    Greetings,
    Bertus
     
  8. eblc1388

    Senior Member

    Nov 28, 2008
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    Tell us whether you want four of those magnets switched together or you want individual control of each magnet?

    Regardless, you will need to get/buy/build a 24V 1A DC power supply as the power source for the magnets.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    If you want to be able to have more than one electromagnet energized at once, you'll have to have a supply capable of handling that much current.

    If you're going to control the electromagnets from a PC, you might consider using logic-level power MOSFETs; something like IRLZ24's would work for that.
     
  10. kiel long

    Thread Starter New Member

    Apr 11, 2009
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    0
    hi everyone thanks for the reply's!!:)
    the magnets will need to be independant...
    so i guess i need to build a 24v dc power supply or atleast a couple... i poped down the local maplins (like radio shack) to see about power supply's today evidently i knew more than the people that work there!!!
    as i say its just the power source thats the need now, (friend said he'd lend me a board to control relays)...
    if i buy a single 24vdc power suply will i be able to send power to 4 relays from this and power the magnets independantly?? eg, buy supply and cut wires, use splitters to the four relays and back into the one... or will this seriously screw the Ω or something ??? (really should have taken electronics and not woodwork!!! i've never needed a bird feeder....:( )
     
  11. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Perhaps this velleman kit is someting to control the relays?
    http://www.maplin.co.uk/Module.aspx?ModuleNo=42857

    It can be connected to the USB of a pc and drive 8 digital outputs.

    You sill need power fets (and the powersupply) to have enough power for the relays.

    Greetings,
    Bertus
     
  12. eblc1388

    Senior Member

    Nov 28, 2008
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    Nope. A single one is sufficient.

    Absolutely. A single 24V 1A power supply will do.

    Wookwork is my favorite subject and I got a distinction in exam doing a "long and short shoulder mortise and tenon joint", basically in layman terms "one corner of a mirror mounting frame". :D:D:D
     
  13. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    How large of an air-gap are you using. Guess you need fast response more than holding power; so put together this ckt. to throw darts at.
     
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