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Topic: Getting and H Bridge Going... (Read 4270 times) previous topic - next topic

braddo_99

Oct 09, 2011, 08:10 am Last Edit: Oct 09, 2011, 02:57 pm by braddo_99 Reason: 1
OK, I'm putting together some thoughts on my first H Bridge. There will ultimately be 4 motors (and bridges), which I think are around 2A - I'm going to finally dig out the better meter and take the car apart tomorrow to verify... I've looked a few places for inspiration on the circuit (thanks Mike, Terry, and dc42), but this is one I keep coming back to:

http://www.cadvision.com/blanchas/hexfet/np-s.htm

Per some advice in another thread, I'm using logic level N Channel MOSFETs and a MOSFET driver for the (non-logic) P Channel, so it's a bit simpler of a circuit than that linked above.

I'm using Fritzing to lay out the breadboard before I actually hook it up and I have a draft (the basic setup with the primary connections and MOSFETS but not all of the diodes/capacitors etc). I'm just wanting to make sure I have the connections I do have correctly mocked up:



N Channel MOSFET:  http://www.irf.com/product-info/datasheets/data/irlb8748pbf.pdf
P Channel MOSFET: http://www.fairchildsemi.com/ds/FQ/FQP47P06.pdf
NPN Driver for P Channel: http://www.fairchildsemi.com/ds/2N%2F2N3904.pdf

Any feedback or suggestions?

By the way, anyone else using Fritzing? I find the breadboard to work pretty well, but the schematic seems to be hopeless. Autoroute seems to draw some lines, but not others. Haven't tried the PCB but not hoping for much. Then you have to move the parts around and try again, which gives a bunch more hopeless lines. You guys using something else? I'll probably end up building it on a strip board anyway so no big deal.

Thanks!


CrossRoads

I use expresspcb for drafting stuff for discussion, then eagle if I am doing something to make a board with.
As an EE I will take the schematic you linked to over a picture of wiring with unlabeled parts every time.

Your picture is too little to make sense of and is not clickable to make larger.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

braddo_99

Thanks CrossRoads - I guess I'm not sure how to make it clickable, but I did set it to display larger,appreciate the heads up on missing the size settings. All of the key components are labeled - I'll also post a link to the transistors below in the original post for clarity.

I can appreciate that it's easier to read the schematic, but my challenge is actually learning to read these schematics myself and translate to the physical understanding. At this stage it's not rocket science, but I'm trying to get to the point that i can keep straight in my head which pin is source vs drain, emitter vs collector and actually wire it correctly!


braddo_99

Wow, a whole day going by with mine the most recent post! Hope everyone is enjoying the last few days before the cold sets in. Cheers.

CrossRoads

Wait - we have a week still, don't we?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

braddo_99

We are enjoying some nice indian summer here as you know if you're in the Boston area. I'm a west coast transplant so fall and winter are  still major bummers for me. Leaves are beautiful for 1 week and then you have to haul them away, snow is gorgeous for 1 hour then you have to shovel it and trounce through smoggy slush for 4 months. I know this is off topic, but just posting for a bump in case I can find takers to let me know if there are any big errors in my mockup breadboard.

I did finally pull the trigger on a bunch of the transistors I linked in the thread, so gearing up for a real prototype build pretty soon.

Grumpy_Mike

Quote
in case I can find takers to let me know if there are any big errors in my mockup breadboard.


I think you have been told that anyone who actually knows about electronics is not going to be able to make sense of a silly practical layout like that.

In order to verify it I would have to turn it back into a schematic by tracing it out and drawing it by hand. Why should I do that when you can't even be bothered to post the schematic that you have made that generated that picture in the first place.

You might not be able to get your head around a schematic but when you do you will find it is the universal language of electronics, one where ideas can be shared and debated.

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