Choosing an H-Bridge

Discussion in 'The Projects Forum' started by kdawg5, Jan 12, 2009.

  1. kdawg5

    Thread Starter New Member

    Nov 16, 2008
    7
    0
    I am running a tiny project where I am trying to build my own Magnetic Levitation System. I know that the max current I want to use is about 5 amps. I will be using a PWM voltage signal which then I want the H-bridge to convert this into current.

    My question is, what kind of h-bridge do I need? or where can I purchase an h-bridge that does this for me? I have been looking into it but all I see are h-bridge amplifiers/ motor drivers/ brushed motor controllers, etc. And I dont know which type I should be using. Any help would be appreciated. Thank You.
     
  2. kdawg5

    Thread Starter New Member

    Nov 16, 2008
    7
    0
    I should also state that the h-bridge is sending the current to a solenoid.
     
  3. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    5 Amps is too heavy for normal transistors..

    Would you mind posting the output section circuit of your project to understand your application?

    These are a few normal H Bridges including 4 transistor and 6 transistor

    http://library.solarbotics.net/circuits/driver_tilden.html

    Replace the normal transistor with a higher power ones or maybe MOSFET
    The one listed above handles 800mA only and with better components upto 2A

    And why do you need an H bridge to control a solenoid???
     
  4. kdawg5

    Thread Starter New Member

    Nov 16, 2008
    7
    0
    i am trying to control the solenoid so that i can make an object oscillate in the magnetic field. all of the documents i found online used an h-bridge and a fellow professor recommended the LMD18201 for my application and reduce the max current to 3 amps.

    I dont know too much about the topic really and was just trying to experiment.

    I am in effect going to use Simulink to program an oscillation of around 1Hz maximum through a PWM signal to the H-bridge which will convert to current and send it through the solenoid. This is the only real way I know how to do it.

    What do you propose?
     
  5. kdawg5

    Thread Starter New Member

    Nov 16, 2008
    7
    0
    to sense the position of the object in levitation I am using a hall effect sensor but I was also looking into light sensing photodiodes too which is another problem because I dont know which type of photodiode to use.
     
  6. Skeebopstop

    Active Member

    Jan 9, 2009
    358
    3
    If you are using an H-Bridge, are you going to use a current sensor in a feedback loop or are you going to use the inductance of the solenoid to determine your output waveform open loop?

    Maybe just buy a DC servo drive and slap it into current control mode :)
     
  7. radhoo

    New Member

    Mar 24, 2009
    3
    0
    A H-bridge is not very complicated to build.

    I've built one recently using 10A transistors to control the geared motors or a robot I'm building.

    See the schematics here:
    http://www.pocketmagic.net/?p=508

    The robot platform controlled by the h-bridge is pictured here, at the bottom of the page:
    http://www.pocketmagic.net/?p=520

    Good luck with that!
     
  8. Skeebopstop

    Active Member

    Jan 9, 2009
    358
    3
    An H-Bridge can be very complicated when you make it robust and versatile, in particular for fast switching applications.

    If it is just a dumb switch yes, it is easy. Otherwise there are many very intricate design techniques which must be used to supress transients to protect driver ICs and the MOSFETs themselves.
     
Loading...