Choosing an H-Bridge

Thread Starter

kdawg5

Joined Nov 16, 2008
7
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.
 

jj_alukkas

Joined Jan 8, 2009
753
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???
 

Thread Starter

kdawg5

Joined Nov 16, 2008
7
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?
 

Thread Starter

kdawg5

Joined Nov 16, 2008
7
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.
 

Skeebopstop

Joined Jan 9, 2009
358
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 :)
 

Skeebopstop

Joined Jan 9, 2009
358
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!
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.
 
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