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Topic: Looking to design/ build a pair of H Bridges (Read 1 time) previous topic - next topic

Krupski


At 14-15amp range, you need fairly beefy mosfets and you will need to use a mosfet gate driver for those things at moderate switching frequencies (1k or up).




Large motors have a lot of inductance. Running the PWM at 1 KHz will make the motors absorb most of the power.

Probably 30 to 60 Hz would be a better range for a large motor.
Gentlemen may prefer Blondes, but Real Men prefer Redheads!

dhenry

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Looking at the maximum rating on the drain, 72A peak, 18A continuous I should be fine right?


Those ratings are typically for pulsed current (5us for example) into a resistive load, and with the case at 25c.

So I typically derate them 50% for my applications. For 15amp current, I use a 30amp (continuous) mosfet.

oric_dan

#12
Dec 05, 2012, 07:23 pm Last Edit: Dec 05, 2012, 07:28 pm by oric_dan(333) Reason: 1
These look like a fairly decent design. They know enough to place a large reservoir cap across the battery
lines [presumed location]. zoomkat, have you actually ever used any of these things yourself?

http://www.ebay.com/itm/30A-H-bridge-Coreless-Motor-Driver-Forward-Reversion-Brake-For-Smart-Car-Arduino-/180983568079?pt=LH_DefaultDomain_0&hash=item2a237616cf

I do like it how so many CN companies include Arduino in the product title even though the thingies have
nothing at all whatsoever to do with Arduino.

You do appear to need 2 different PWM signals to the board, and what are the parameters of the current
and voltage signal out? Unfortunately, they rarely seem to have much documentation.
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V +                Power Input +
GND             Power Input -
EN                 Driver Enable, high enable, low off
RPWM          Forward PWM input, high active
LPWM          Reverse PWM input, active high
CT                 Current signal output,analog signal
VT                 Voltage signal output, analog signal


dhenry

A discrete h-bridge is fairly difficult to design, primarily to get it to switch fast and to allow for the appropriate dead time.

If you are starting now, I would recommend that you look into h-bridge drivers (high/low-side drivers). They come in many different shapes, depending on your needs.

Generally, you need to decide if you want to have braking / motor hold; if you want to be able to drive high/low sides separately; if you allow enable signaling or not; your desired voltage ratings and if you want under/over voltage protection, etc.

Many firms offer such chips and they are generally easy to use. IRF, Fairchild and On would be good starting points.

Grumpy_Mike


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You would do well to heed this advice.


Wow, someone actually agreed with me this week! LOL.

Well add me to your list. Playing about with this sort of current is not trivial.
One thing that it is hard to get over to beginners is that electronics do not scale up easly.

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