Let's Make Robots!

I need to build a BIG motor controller

Simple question,

I need to run a motor drawing between 7 and 10 amps at about 18 volts. (I think a similar question has come up reciently)

I am looking a these which is a big brother to the L293D. It says it will handle 2 amps per channel.

Question: Is it as simple as ganging up in 5 of these units in paralell to get my 10 amps? 


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Distributors usually have large catalogs of many different parts, passives to ICs to connectors to whatever. Some send free, others want to charge a bit to be taken off your first order, some have minimum order dollar amounts.

Mouser http://www.mouser.com/   local guys to me, no minimum, links to datasheets online

Digikey http://www.digikey.com/  been pretty standard, no minimum, links to datasheets online

Allied http://www.alliedelec.com/  also local, can be high

Jameco http://www.jameco.com/ almost tends to hobbiest

Newark http://www.newark.com/   


Manufacturers - sometimes data catalogs, product offering "brochures" (in a 3 ring binder)

National Semiconductor http:/www.national.com/   variety micros, analog, power, FETs

International Rectifier http://www.irf.com/  FETs, FET drivers,  FETS, power semiconductors.. and FETs

Intersil http://www.intersil.com/  HIP4081 many others

Infineon http://www.infineon.com/  monolithic h-bridges

Motorola http://www.motorola.com/ micros, and some power even

I'm right there with  you Chris, I am so confused on some of these topics on motor control. Alas I'm even further behind, I'm ordering my PICAXE tomorrow.../sigh

I had a question on the posted schematic, why are there 4 PWM inputs on that H-Bridge? 

What I'd like to try is putting together schematics and parts lists for 3 different h-bridges. In the posts, I've mixed a couple parts up, and have noticed different parts where they shouldn't be. Like the schottky diodes, they really should be for the relay h-bridge, and not necessarily for a FET h-bridge, and need a matching set of common anode diodes needed too. And the low side driver also for a FET under relay h-bridge, but could be used on a P over N h-bridge too.

BOAs relay h-bridge is a good idea, and workable,  and just a few parts could be added to it. That would be a first possible draw-up.

Putting together a P over N h-bridge using the TC4427 (or close relative) would be another possible design, though it would probably be limited to 12 volts.

And finally drawing up an all N-channel FET h-bridge based on an actual high and low side driver (IR2184 (not IRF) or an HIP4080 or HIP4081)

Will need a bit for parts lists, but does this sound reasonable?

Oh, some great information on learning about h-bridge is found in an application note for the LMD18200

BOA's relay H-bridge is not only workable: it's a reality. I came up with it after I'd been down all the roads CtC is currently exploring, having decided they were all too complicated or too expensive!

Chris, I tried to make your life easy, but you have chosen the difficult path, my child. I hope you fare better than I.

I'll tell you what, BOA...

I think in the end, I will probably go with your hybrid design (just substituting some higher amperage FET's -it sure has gotten a lot of praise...That being said, and the path I have chosen, I am stoked to try to learn how the whole system works (in a full H-bridge form) and how each part does it's thing and I expect a few meltdowns allong the way. If nothing else, there has been at least a few suggestions of additions to your design that I want to look into. I dunno, if I just copy a schematic and solder it up it's really nothing more than following a recipe.

...Ah, I must learn first, young grasshoppah...

high side, low side... Now I am really confused... there is no positive/negitive on the gate... isn't a n-channel negitive to open and p-channel positive to open? Damnit! I SWEAR I am going to figure this out! --Well, I do love puzzels!


Ok, robotologist, I think I got this high side low side stuff... The high side is switching the + on and off and the low is ground. If indeed I need a half and half driver there is a TC4428 which is half straight and half inverted. --Probably what I should be looking at. Or maybe I should go back to considering the relay idea. I swear, the more I learn about this stuff the more I find I don't know.

Oh, and one request.... When you guys suggest a part i.e. schottky rectifier or whatever, would you be so kind as to include a googleable part number? --It REALLY helps me a lot when I can find a data sheet that I can study. Remember folks, you have to give me my homework to do.


Well, I found this and it seems to include everything we have been talking about.




I think I will be working with this basic schematic to start building my controller.

If you guys would, below is my list of stuff to order including in bold the items you guys have suggested and where I am going to substitute for the parts listed above. If you could check my math here, I would love you guys for ever and ever.                           (Assume I am doubling all of this as I will be driving 2 motors)

Instead of the IRLZ44's or IRF3xxx's I am using (4) IRF2804

Instead of the (4) 1N4005 (D1-D4) I am using the MBR20150CT **I still don't understand the pin-out of this unit. It shows both diodes shooting to eachother meeting on the middle pin. It seems that I need them both facing the same direction as shown above. Do I need a total of 4 -using only 2 pins of each?

Instead of the National FET Driver DS0026 I am using a TC4427 **Now, I am led to believe through what I have read and what is on the schematic above, that the IRF2804 is a N-Channel and needs the gate to be pulled to ground to open the source to the drain. If this is true, and the PWM comming out of my Picaxe is a + logic signal, do I need to get the TC4426 instead of the TC4427 as it is an "inverting" unit? Again, I am led to believe that if V+ Logic is comming in and I need to switch ground on and off to run the IRF2804, I would need to invert. --I dunno, just tell me which one to get.

The rest of the stuff shown above seems to all be self-explainitory, caps and the smaller flyback diodes going around the FET's themselves. --I think I got that figured out and covered.

And just one more: I would assume that (as shown above) PWM input A and C should be tied together and PWM input B and D should be tied together. No?


--That should do it! I can't tell you guys how much I appreciate how much help you have been on this and all my other projects, Thanks. Like I said above, just let me know if I am on the right track and I will get this order, well, ordered!! --I can not wait to start etching the board!!!!!!!

Can any of the Uber-Boffins comment on the use of Rb and Rt? Presumably that's how the gate voltages are regulated after the charge pumps. Can this work? What would the PWM Vpk-pk be?
The front end to the FETs seems very strange in that diagram, and usually resistors, particular 100 k ones, only serve to slow turn off times configured as shown. I glanced at the part that is to be attached to it, but haven't any clues from that.