Designing 46 Amps power supply

Discussion in 'Embedded Systems and Microcontrollers' started by prabhubng, Mar 22, 2013.

  1. prabhubng

    Thread Starter New Member

    Sep 29, 2009

    I am a newbie to electronics.

    Currently I have developed a project in which I have 268 solenoids needs to be actuated at positive and negative power, for which I am in the need of designing a split rail power supply which can give me +12v and -12v.

    The resistance of each solenoid is 70 Ohms, so at 12v I should be able to drive each at 0.171 mA current, so in total 45.828 Amps current is required to drive all the solenoids, I am completely very beginner to electrical designs, so can someone please guide me on this design, any reference will be really great help.

    Thanks in Advance,
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    With split supplies, some of that 45.828 amps comes from the +12V and the rest comes from the -12V. How much depends on how many relays run off each.

    With split supplies, the control for the relays is more complicated then a single supply. Transistors would require a level translation from negative to positive domains.

    With split supplies, you need two supplies. While each is smaller then one supply they will cost more then one supply.

    With split supplies, even with single supplies, especially at higher currents, the design is a specialty in and of itself. You will save time trouble and money by purchasing a supply capable of deviling your necessary current.
  3. codeboy2k

    New Member

    Jun 18, 2012
    First, I have to ask what are you doing with so many relays? More information would help us answer you better.

    Note that you only need that much current if you intend to activate and hold all the relays simultaneously. You can save on current needs if you use a solenoid that holds its position when the current is removed.

    I don't know why you need +12 and -12, unless you actually do have a bi-wound solenoid, with a center tap, and it's bidirectional, in that case you really need a way to switch a single 12V supply to different coils on a single solenoid, in order to "pull-in" or "push-out".

    If you have an array of solenoids flipping some physical bits, similar to a train station or airport sign board, and if you can design it to cycle down an array, then you only need as much current for one row or column of relays. Even still, if your design can afford the time required to change one solenoid at a time, then you only need enough current for 1 solenoid (+ extra for control signals, if any).

    Finally, if you do decide you need approx. 48A +-12V supply, you should look towards a ready made switch-mode supply. High current linear supplies that don't fail are hard to build right, and you don't really need well regulated linear supply for solenoids anyways. If you can use some of my ideas above to reduce the current requirements you can easily find an inexpensive 12V 10A (120W) or 12V 5A (60W) switchmode power supply, i.e. what ever you can lower the requirement too, if at all.
  4. rodrider

    New Member

    Oct 31, 2012
    First you need a transformer that can provide such a current and such transformers are bulky
  5. BillO

    Well-Known Member

    Nov 24, 2008
    268 relays!!! Mother of all that is good, what are you building?!!?

    I would not use a transformer for this, or try to build my own regulator. A 30V 50A CT transformer will cost and arm and a leg and weigh about 30kg.

    Two of these connected together would be a lot cheaper and easier to do.
    Last edited: Jun 25, 2013
  6. Papabravo


    Feb 24, 2006
    Why not have 268 Twelve volt power supplies. It will be much easier to construct and troubleshoot. It will be more fault tolerant due to the level of redundancy.

    If you don't like that approach, I'm thinking that some number of 12 V power supplies between 1 and 268 might represent an optimal solution.
    ErnieM likes this.