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Topic: H-Bridge shield - large motor control for arduino (Read 5920 times) previous topic - next topic

__ag

Hi all,

i've just finished an h-bridge shield for large motors
all related info here:
http://www.andregoncalves.info/ag_blog/?page_id=67

let me know if you have any comments, suggestions, improvements...

best regards
andre

westfw

Pretty nice.  I particularly like that you managed to make the PCB single-sided.  Though I dislike that it looks like the tabs of the transistors nearly short the leads of the transistors next to them (probably mount them upright - this isn't a shield that ought to be stacked anyway, given the need for some air circulation.)

Also thanks for the pointer to Chuck's site (originator of the circuit.)  His writeup explaining the whole thing is pretty exceptional!

mowcius

I have a quick question, what is the maximum current draw from that board? (at about 9v)

Is there a brd file available?

Mowcius

westfw

About 5 to 6A if you add adequate heatsinks.  2A or so without heatsinks.

__ag

thanks for the comments,

i sorted out those tabs that seemed close to a short circuit, with better bending they fit totally flat now.
Ofcourse, like westfw mentioned, this is a good option when you're not driving too much current, if you need all the extra juice that it can provide then having them upright is the way to go, also a fan blowing air through them is always a good option, i never planned to install heatsinks in them but i'll see if i can find some that will fit and have that as an option!

also updated the webpage with a *warning about this

and thanks westfw for the prompt help with current consumption

.brd file will be uploaded to the website soon

best
andre

__ag

Hello all,
just to let know that i made available schematics and board files on the website!
best*
andre

westfw

Thanks!  I've had fun playing with the pcb layout (more details if I get anywhere interesting.)
But in the process of the closer examination, I have a new criticism...

In Chuck's original design, one of the features is that the motor circuitry is completely isolated (optically) from the motor circuitry, including the motor power supply.  But you've connected the motor "Gnd" side and the Arduino GND.  Not only that, but it looks like the motor power ends up going through the arduino board gnd connections (due to using both upper and lower GND pins to ease the layout.)  This makes me nervous...

__ag

Hello,
you are so right!
no harm done because i haven't sold any, i'll make a revision and correct that, i should have use two different ground lines in the schematic, that's what made me mix them up, i had previous versions of the circuit where i had this in mind when designing the pcb, think i just forgot...
failure is always the best way to learn!
thanks for pointing that out!
best
andre

__ag

In fact it's quite easy to change the existing pcb in order to correct that, 2 cuts and a jumper wire.
done!
thanks again!

mowcius

Quote
failure is always the best way to learn!

Indeed it is but unfortunately it can also be expensive!

sasaa

i would buy one from you if it had a second h-bridge for steering/or for stepper motor use

i know i could just have to but i can bearly fit a proto-shield + mini breadboard in my robot.

I think i'll create a shield with 2 h-bridge's or get the (les powerfull) motor shield.

mowcius

Quote
I think i'll create a shield with 2 h-bridge's or get the (les powerfull) motor shield.

The motor shields are typically rather low powered :( Unfortunately I have not used my in a project yet as it has not been powerful enough. I need to just build myself a little robot to use it with.

I would have thought that you would normally use a servo for steering in which case you would not need a shield, you can just plug it into a pin that is not used for the H-Bridge shield.

I think that a stepper for steering would not be such a good idea unless you have some kind of sensor and adjustement routine at the start of your code to get it back in the middle. A servo will always go to the position asked for (within a small percentage error).

Mowcius

kunkmiester

Something else is you might set up a header or two to make it easier to plug in a couple of servos.

You kind of got an idea I'm not yet up to developing--a two bridge shield that's set up so that you can solder on anything from small transistors for running little 3 volt motors to big MOSFETs connected directly to heavy gauge wire for very heavy loads.  The idea was a single board could make several different H-bridge controllers, which means you could get higher volumes made, leading to lower prices per board, and thus per controller.

I'm still working on some programming though, so I'm not yet ready to tackle a hardware project like this.  Might end up using one of yours if I need something that big. ;)

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