DIYMark

First off, dont try any of this is you dont know what im talking about (BLDC driver electronics) becuase you may head of and break/damage your equipment if you decide to copy me and i wouldnt want that to happen, however if you have a good amount of electronics knowledge you could possiblly try this and have a nice esc as a result.

Well after having a huge BLDC motor sitting in my shed, ive decided to make it turn :P with my own bldc controller. The motor im talking about is a non rc one but it is a huge outrunner that is 12 inches in diameter and 3 inches thick!!!! imagine the huge prop this would spin - probally could make an ultra light out of it or a 50% 3D plane LOL...

Anyway, i searched the semiconductor brands for BLDC drivers and orderd the best one i could find. Etched up a board and built it with the capability to drive a motor that was 140volts and 20amps (40amps wit ha slight mod) i had to mod the circuit due to the high power capabilities. And when it came to testing it i hit a problem...the driver was hall sensored (no sensorless ones could be found) and the sensor phasings were wierd, like 15 degrees instead of the typical 0, 120 and 240. So this made the controller i spent time building useless...or did it.

I searched google for a back emf circuit to replace the hall sensors but no luck, so next ill try moving the sensors, i figured it would still work but anyway i will have messy sensor wirng to deal with...sensorless would be best!!!

Nether the less ill try moving them, but this problem also go me thinking, i can convert the crappest bldc rc plane/car controller into one that would be as good as any of the best controllers, if not better (theorticaly).

Okay it starts out with a BLDC esc...even if you have the crappest and lowest current rating one you could be able to convert it to a high current/voltage one (provided that the board isnt to small and you will still be able to solder a wire to some of the tracks).

Now im not going to go into any great details but if you know enough about BLDC you should be able to know how to do this (its not simple if your a beginner to electronics and sorry for the lack of diagrams - might add some later).

so now you have the esc (20 amp one is a good size to work with) you will have to open it up to get to the board. Have a look and you should work out where the ic pins lead onto the 3 phase h bridge. now this is where you have to "intercept" the signals. you can either desolder the mosfets or cut the tracks with a knife.

now you have to make your own h bridge.

See the digram for the schematic if you need some prompting, but you will have to make this onto your own board (or aluminium plate as a heatsink and just wire them together - same thing but a pcb is neater).

The power supply can be whatever you want it to be BUT the transistors/mosfets for the h bridge you choose must be able to handle the power levels you want.

In my version for non plane use i wanted 120 volts 7.5 amps, the best transistors for this use were MJ10053 and MJ15004 (140 volt, 20 amps).

So here i have some room to work with.

Also you may have found transistor/mosfets that are only half the current you want to use, so in this case to can join 2 in parallel and use them as 1 (be sure to match the transistor/mosfets if you choose to do this).

Also mosfets are better than transitors becuase of the lower internal resistance and thus more efficency (less heat from resistance).

so now once you have built up the h bridge it time to solder the purple (see diagram) leads to the correct copper track that was leading to the previous esc's mosfets. You will have to double check be and makesure they are right by inspection and however the manufactuer decided to wire theirs.

And you will have to connect the green leads (see diagram) to the esc's EMF Inputs on the IC.

Now seeing as were trying to get high power use from a low power esc the voltage used for the h bridge is different to the voltage used by the driver. So now you will need 2 power supplies (this is the downside). Or you can tap the drivers supply of a few cells from the h bridge supply. Also both power supplies must be connected to the same ground - the "pluses" goes to the driver and h bridge..but the "minus's" tareo be shared (connected to ground).

Now due to the mods the esc may be a bit bigger (addded mosfets and not as practical due to 2 power supplies) but if you have a bldc esc hanging around you could try this and have some fun

There is room for improvement here, like to heat sink the power drivers, make another small circuit to regulate and dropdown the h bridge supply for use on the driver (esc), etc.

but all i intended to do here was to share my thoughts on what could be done to improve (allow for higher power levels) of a lower rated esc.

Of course buying a better esc would be ideal, but the savings you could make here could be heaps! at the cost of practiacally (unless you want to add an extra regulator, encloseure - not that much harder).

Anyway good luck if you try this (i might be soon) and i can offer some help but i dont really want to write up a comprehensive guide just my ideas...

and if you under stood what i was crapping on about i think that you could do this with sucess

now time to wait for the onslaught of replys to various things i may have got wrong...

PS - Sorry for the crude block diagrams but if your capable of understanding this modifications you should be able to know how to do this with some electronics know how

rsilva

If you want to learn and teach you can visit bldc.wikidot.com. Or just follow the links about BLDC motors.

wlester

Just A thought, but you might try a near by motor repair shop and find a junked 3 phase motor speed controller to skarf a high powered mosfet bridge and the asscoiated photo isolated drivers needed.
The newer "throw away units" have been getting smaller and smaller while still handeling amazing amounts of current.

Wes