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Topic: H-Bridge with High Current Transistors (Read 17307 times) previous topic - next topic

zoomkat

Below are some high current transistors, a good read on a DIY H-bridge project, and a high current H-bridge that might meet your needs when your DIY project most likely fails.

https://www.sparkfun.com/products/10213

https://www.sparkfun.com/products/10349

http://forum.arduino.cc/index.php?topic=53425.0

http://www.ebay.com/sch/i.html?_sacat=0&_from=R40&_nkw=BTS7960B+driver&_sop=15
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MarkT

Perhaps the easiest way to build an H-bridge from discrete components is to start with
good MOSFET H-bridge or half-H-bridge driver chips(*), add 4 n-channel MOSFETS
well up to the power and current and voltage ratings, and follow the suggested circuits
in the driver datasheets.  If you have a supply of limited current-sourcing ability
that will help prevent expensive mistakes (lead-acid and lithium batteries are not
forgiving).

(*) Ones with shoot-through prevention preferably - look at the datasheet for
the HIP4081A for a start.

Alternatively the VNH5019 does it all in one package:
http://www.pololu.com/product/1451

(Its actually 4 MOSFETs and a driver chip packaged together)
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Domino60

Well because I will anyway gonna turn the polarity of the motor manualy, I'm gonna use a Transistor to control
the voltage of the motor when I need it to be ON and OFF and I'm gonna rivers the polarity of the motor with a
DPDT switch. So I'm gonna put a button to control the motor state (ON/OFF) and a DPDT switch to control the
rotation of the motor (Right/Left).

That's what I'm thinking, so I'm gonna spend about 2~4$ for each motor system.
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keeper63


Perhaps the easiest way to build an H-bridge from discrete components is to start with
good MOSFET H-bridge or half-H-bridge driver chips(*), add 4 n-channel MOSFETS
well up to the power and current and voltage ratings, and follow the suggested circuits
in the driver datasheets.  If you have a supply of limited current-sourcing ability
that will help prevent expensive mistakes (lead-acid and lithium batteries are not
forgiving).


I'm going to second this, with the following extra bit: Size the FETs 4 or 5 times larger than your current needs (so you want 10A - pick 50A n-channel FETs). That will give you plenty of breathing room, and it won't be that much extra to spend. You likely won't need heatsinks for a FET h-bridge (with the larger FETs and the smaller current needs), but you might want to leave room for them just in case (or if you want to use it with even larger motors later).

That said - you would still likely to be better off purchasing an h-bridge; since you don't want to go down this route, purchase plenty of spare FETs for the inevitable destruction as you test and play with the h-bridge you do build.
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dave-in-nj



Perhaps the easiest way to build an H-bridge from discrete components is to start with
good MOSFET H-bridge or half-H-bridge driver chips(*), add 4 n-channel MOSFETS
well up to the power and current and voltage ratings, and follow the suggested circuits
in the driver datasheets.  If you have a supply of limited current-sourcing ability
that will help prevent expensive mistakes (lead-acid and lithium batteries are not
forgiving).


I'm going to second this, with the following extra bit: Size the FETs 4 or 5 times larger than your current needs (so you want 10A - pick 50A n-channel FETs). That will give you plenty of breathing room, and it won't be that much extra to spend. You likely won't need heatsinks for a FET h-bridge (with the larger FETs and the smaller current needs), but you might want to leave room for them just in case (or if you want to use it with even larger motors later).

That said - you would still likely to be better off purchasing an h-bridge; since you don't want to go down this route, purchase plenty of spare FETs for the inevitable destruction as you test and play with the h-bridge you do build.


I would go along with this with a caveat.   READ THE DATA SHEET
many FET's are advertised as 50 amp, and then you find out that is good for pulsed operation with a 10% duty cycle. and the FET is rated for 8 amps at 100% duty cycle.   Many are being advertised as the 100% duty cycle, but this only takes a few seconds to verify before purchase.


Grumpy_Mike

You can always use a relay to reverse the direction and a transistor to turn it on and off.
Have you seen this:-
http://www.thebox.myzen.co.uk/Workshop/Motors_1.html

luisilva

Grumpy_Mike, I don't like the option of relay to substitutes of transistors or for H bridges. You can't control the velocity (with PWM, for example) of the motors.

Grumpy_Mike

Quote
You can't control the velocity (with PWM, for example) of the motors.

Of course you can. I said:-
Quote
You can always use a relay to reverse the direction and a transistor to turn it on and off.

You apply the PWM to the transistor turning the motor on an off and the relay for the direction.

Quote
I don't like the option of .......

Yes but it is not your thread so I care little about what you like or don't. Any real valid reasons?

knut_ny

..and there is now a small problem:
What voltage will be suitable for controlling base-inputs when motor run from e.g. 12V ?
(I guess additional components adds to the bill..)
Ny

runaway_pancake

#24
Jun 22, 2014, 02:11 am Last Edit: Jun 22, 2014, 02:35 am by Runaway Pancake Reason: 1

Grumpy_Mike, I don't like the option of relay to substitutes of transistors or for H bridges. You can't control the velocity (with PWM, for example) of the motors.


Au contraire.

In the dwg (attached), I show an NPN, but that could be a "logic-level FET".

> > > 1A and 1B would be on together, 2A and 2B would be on together.  Steady on.
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

luisilva

#25
Jun 22, 2014, 02:36 am Last Edit: Jun 22, 2014, 02:46 am by luisilva Reason: 1
After see the picture of Runaway Pancake, I must say that it seams that both of you ARE RIGHT! I didn't get it.
But I still don't like it for the other reasons that I point, and because I think that is "catching a fly with a hammer". That is, if you only need 4 switches why you should use 5? Is a assembly so important, so useful, and so well known that I don't remember of saw it ever. But yes, I shall admit that is possible.

@knut_ny: any voltage that can produce enough current in the base capable of put the transistor in the saturation. That is you must "play" with the voltage that you have in the base (constant) and the base resistor (that can be variable until you reach the current you want). If your base source cant source that current, yes, you need to add more components (more transistor in, for example, a Darlington pair)

knut_ny

..we are far off target now..but:
the "simple solution" may not be suited for arduinos digital outputs..
-----------
reading OPs problem.. I believe I'd go for a prebuilt, advanced soulutionfor moto control..  (the end)
Ny

runaway_pancake

http://www.rambal.com/descargas/libros/Nuts%20and%20Volts/2/Stamp%20Controlled%20High%20Power%20H-Bridge.pdf

"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

westfw

Quote
that is 10W per transistor.

There are surely bipolar transistors that will run a 10W dissipation with a suitable heat-sink.   You just have to be prepared for the heatsink to be significantly large.   After all, I have a lab-style power supply that claims to deliver 5A, and I'm pretty sure it operates its output transistor at more than 2V Vce a lot of the time.

It'll depend on how much you're willing to experiment :-)

grab a couple 2n2955 (PNP) and 2n3055 (NPN) transistors (or the more modernly-packaged equivalents) (these are ancient and have rather poor performance, but they should be very common), set them up about like here: http://www.pocketmagic.net/2009/03/a-simple-h-bridge-design/
And use a smaller H-bridge chip (293L or whatever) to drive them instead of the 2n5551s (as per MarkT)

Quote
I don't like the option of relay to substitutes of transistors or for H bridges. You can't control the velocity

You use the relay to reverse direction, and a conventional (single) transistor or MOSFET to do the PWM.  This requires that you don't need to reverse directions quickly or often (like in an RC car, but NOT like for a stepper.)  This simplifies the circuit complexity and reduces the power waste by at least a factor of two.

zoomkat

You could get a log level MOSFET to control the PWM, A dual relay board like below to reverse motor direction, and wire the relays like in the pix for a simple setup.

http://www.ebay.com/sch/i.html?_sacat=0&_from=R40&LH_BIN=1&_nkw=arduino+relay+2&_sop=15


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