Author Topic: High current h bridge?  (Read 5050 times)

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Offline Half ShellTopic starter

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High current h bridge?
« on: November 29, 2007, 01:09:17 PM »
Hey, I'm trying to find a high current (up to 14 amps, prob around 7 volts) h bridges. I'm more looking for a friend but any help is appreciated.

Cost should be kept down, but isn't critical. Thanks!

Offline bens

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Re: High current h bridge?
« Reply #1 on: November 29, 2007, 02:18:03 PM »
ST's VNH2SP30 and VNH3SP30 are right in that ballpark.  Pololu has dual and single VNH carrier boards that let you do 30 A max and around 14 A continuous (VNH2 only, VNH3 can do up to 9 A continuous) without a heat sink.  If you added a heat sink you could raise the continuous current rating to something closer to the 30 A max.

Offline Half ShellTopic starter

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Re: High current h bridge?
« Reply #2 on: November 29, 2007, 02:32:18 PM »
Thanks, but are there cheaper solutions? I'm used to the 4 dollar 1 amp SN75440NE that controls two motors, but this 35 to 50 dollars!

Offline bens

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Re: High current h bridge?
« Reply #3 on: November 29, 2007, 03:44:45 PM »
Well, digikey wells the VNH2s (each IC contains a single H bridge) for a unit price of $10.51 (and VNH3s for 8.26 each), so I suppose you could buy the chip and surface-mount it yourself to a PCB.  I'm not sure what other high current H bridges are out there, but I expect the prices would be similar to this.  Driving a motor at 14 A continuous is much harder than driving a motor at 1 A continuous.

Offline Half ShellTopic starter

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Re: High current h bridge?
« Reply #4 on: November 30, 2007, 09:55:29 AM »
Alright, I think I've got what I need. I'll be using just the stand alone chip and wiring it myself andwhatnot. Thanks bens!

Offline Half ShellTopic starter

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Re: High current h bridge?
« Reply #5 on: November 30, 2007, 12:19:28 PM »
Hold up, I was reading the data sheet for the VNH3 and VNH2, they both say they can hold 30 amps continuous - does it still require the heatsink when going above 9 amps because it isn't mentioned there?

Offline bens

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Re: High current h bridge?
« Reply #6 on: November 30, 2007, 02:16:16 PM »
For you it might require a heat sink before 9 amps.  The carrier boards I linked to in my first post cool the chips by acting as a heat sink, allowing them to reach the current levels I listed without overheating.  The chip by itself could very well overheat at lower currents.

Offline Admin

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Re: High current h bridge?
« Reply #7 on: November 30, 2007, 05:23:16 PM »
In the datasheet look for something probably called 'power rating' or 'power dissapation'. It will be near where it says 'maximum voltage', etc.

The chip can only dissapate so much heat to the atmosphere at any point in time.

To know how much power you are putting through the chip, multiply expected voltage x expected current.

Power = voltage * current

If the power you need is below the power rating, you will not need a heat sink.

 


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