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Topic: Is arduino fast enough to handle brushless motors commutation?! (Read 1 time) previous topic - next topic

Senso

The C compiler might not be able to create code that fits in the 250 cycle space, because all the ESC's that have open source code are coded in assembly, also almost all ESC's use atmega8's as said and running at only 8Mhz using the internal oscillator, so 16Mhz is a lot more time.

Ludo91

What about connecting the arduino pwms to the mosfet? I was thinking of useing a "pre-amp" stages made with transistor in order to keep the arduino away from the mosfets` gate saturation current (very high on 400A mosfets) and make a quicker switch. Am I on the right path?


In order to pick the right components i`ll refer to some datasheets and guides from national rectifiers and others.

I have some "ideal assembly" knowledge (part of a college exam), reading datasheets etc i may be able to write the code/part of it in assembler.
If needed i`ll get into it and, eventually, ask for help on the forum if i won't manage to figure it out myself


MarkT

Typically a specialised driver chip(s) is needed - both to handle the high currents, boost the gate voltage to 10--12V and drive a charge pump to provide gate voltage for high-side n-channel MOSFETs.  IIRC one 3-phase driver chip is the HIP4086.

Be aware that high current MOSFET circuits are totally unforgiving of error - always limit the current during testing and development till you are sure all is well.  If you don't something will melt or explode.  Start with 100mA load, then 1A, then 5A, checking all the time for unexpected behaviour or overheating.

This is not an easy project.
[ I won't respond to messages, use the forum please ]

Senso

Some handy links:
http://www.rcgroups.com/forums/showthread.php?t=1384442
http://www.rcgroups.com/forums/showthread.php?t=1378680
http://www.rcgroups.com/forums/showthread.php?t=766589

The first two links have zip files and pdf files, they have both schematics and source code, there is also a fully designed i2c controled ESC based in a pic30f ou 33 dont remember correctly.

Ludo91

tnks guys :)
Tnks for the link also, they refer to great technical works but are pretty different from my goal, I want to make a sensored controller to use on a ebike. I used to run it on a sensorless rc controller, it worked great but with the (big) limit that I had to run it at about 10mph before the back emf was strong enough to make a sensorless controller work.

Is there any ic that can help me connecting a logic pin (arduino output) to the mosfet gate?
I think I could solve this issue using logic level gate mosfets, but seems I`m wrong  :(

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