Hi Folks,

I need a motor controller for a 60A RC airplane motor. As always, it won't be used for it's intended purpose.

A soft start mechanism would probably be nice so it doesn't tear itself apart. Otherwise it is just on/off. I can program PICs, AVRs, etc... I just want to build something that is already done and tested. These $100 ESCs are ridiculous for what they are... Although..... In that regard..... What's stopping me from changing the fets on some $20 1A unit?

 

Most of the newer high power RC motors are brushless DC type that do require a different type of ESC (3 phase control) then normal brushed DC motors (single phase control). Can you give specific motor details?

Lefty

 

I am fairly certain most if not all are of 3 pole design. I think brushed motors have gone the way of the dodo. There are no internal sensors to determine timing, it appears as though that's sensed through back EMF. I can't give much more details than that, the motor manufacturers don't list anything on their websites, besides current, voltage, and rpm/volt.

 

go to the Microchip website and type "BLDC" into their search engine. You'll find a wealth of application notes, source code, schematics and very informative tutorials on how to use PIC devices to control Brushless DC motors.

 

3-phase you mean, not 3 pole.

THe footprint first of all, and the fact that largers FETs switch slower and require stronger gate drive circuits.

BUt anyways, consider that you have to make the PCB yourself and it has to be able to carry 60A (not to mention design time which means you would need to come up with a sensorless commutation circuit, etc, etc.). If you made the PCB yourself, would it still be more economical to build one than just to buy a commercial RC ESC? Probably not. I was looking at the cost to make my own, and the majority of the cost is in the high current PCB (and maybe the FETs if you use 30 FETs in parallel like the RC ESCs do, rather than one or two larger, more expensive FETs.)

To be honest, I'm not sure how the commercial RC ESCs manage to carry so much current on such a small PCB, unless they are using 6oz copper in which case it will definately cost you many many times more since they are mass producing them, and will have much cheaper PCBs than you can get.

 

Actually they are probably quite good value for money!.

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60A damb!! what kind of torque are you getting from that, cause you are going to be loosing a fair few volts in the leads which could of been used to get the machine to speed

Unless you are commited to this motor I would suggest getting a DC-DC converter and boosting that 12V upto something a bit more helpful and getting a different machine.

Sure you will gain weight in the DC-DC but you will easily recover that in a smaller machine and in the reduction in cabling diameter (if you hood the DC-DC right up close to the battery... that would still draw 60A if that power rating is right).

But yer get a self-contained BLDC controller. However fun they are to build from scratch you are going to get issues and waste alot of money in dead devices

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Heres a link to a website with heaps of info on speed controllers http://homepages.which.net/~paul.hil...llersBody.html

I did have a link to a pic based ESC but the page has disappeared from the web. Anyway have a good read of the link and with some thought you should be able to design your own.

Hope this helps

Cheers Bryan

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