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  • Jaronv's instructable Upgrade/Replace Brushless Motor Magnets's weekly stats: 2 years ago
    • Upgrade/Replace Brushless Motor Magnets
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      20 comments
  • Jaronv commented on Jaronv's instructable Upgrade/Replace Brushless Motor Magnets2 years ago
    Upgrade/Replace Brushless Motor Magnets

    The motor controller uses the back-emf method. What I meant by the second thing I did was I changed the voltage divider of the feedback (like you suggested).The board looks just like this schematic I found:https://static.rcgroups.net/forums/attachments/2/3...The original voltage divider was with 12k (10k in schematic I found) to ground and 33k to signal. (which makes sense if back EMF is around 12v) I changed that to 4.7k to ground and 33k to signal.The signal goes to the input of the microcontroller via a 33k resistor, I don't know why, is that just protection? (I tried bridging this resistor but it still spazzes out)However, I can't replicate the same starting up of the motor and then slowing down that I mentioned in my previous comment. When I try it now it just starts spazzing out a...

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    The motor controller uses the back-emf method. What I meant by the second thing I did was I changed the voltage divider of the feedback (like you suggested).The board looks just like this schematic I found:https://static.rcgroups.net/forums/attachments/2/3...The original voltage divider was with 12k (10k in schematic I found) to ground and 33k to signal. (which makes sense if back EMF is around 12v) I changed that to 4.7k to ground and 33k to signal.The signal goes to the input of the microcontroller via a 33k resistor, I don't know why, is that just protection? (I tried bridging this resistor but it still spazzes out)However, I can't replicate the same starting up of the motor and then slowing down that I mentioned in my previous comment. When I try it now it just starts spazzing out again. (I played around with resistor placements and values that day so I don't know for sure when that happened)What I also found peculiar is that one of the back emf pins on the microcontroller is not an analog pin.What voltage can I expect for back EMF, is it generally a lower or higher voltage than source?I am actually a second year Electrical engineering student :)

    The motor controller uses the back-emf method. What I meant bythe second thing I did was I changed the voltage divider of the feedback (likeyou suggested).The boardlooks just like this schematic I found:https://static.rcgroups.net/forums/attachments/2/3...Theoriginal voltage divider was with 12k (10k in schematic I found) to ground and33k to signal. (which makes sense if back EMF is around 12v) I changed that to4.7k to ground and 33k to signal.Thesignal goes to the input of the microcontroller via a 33k resistor, I don't knowwhy, is that just protection? (I tried bridging this resistor but it stillspazzes out)However,I can't replicate the same starting up of the motor and then slowing down thatI mentioned in my previous comment. When I try it now it just starts spazzing outagain. (I pla...

    see more »

    The motor controller uses the back-emf method. What I meant bythe second thing I did was I changed the voltage divider of the feedback (likeyou suggested).The boardlooks just like this schematic I found:https://static.rcgroups.net/forums/attachments/2/3...Theoriginal voltage divider was with 12k (10k in schematic I found) to ground and33k to signal. (which makes sense if back EMF is around 12v) I changed that to4.7k to ground and 33k to signal.Thesignal goes to the input of the microcontroller via a 33k resistor, I don't knowwhy, is that just protection? (I tried bridging this resistor but it stillspazzes out)However,I can't replicate the same starting up of the motor and then slowing down thatI mentioned in my previous comment. When I try it now it just starts spazzing outagain. (I played around with resistor placements and values that day so I don'tknow for sure when that happened)What Ialso found peculiar is that one of the back emf pins on the microcontroller isnot an analog pin.Whatvoltage can I expect for back EMF, is it generally a lower or higher voltagethan source?I amactually a second year Electrical engineering student :)

    Yes, I forgot to put this in the document but you are right. I alternate the poles every time so next to one magnet that has north facing inwards there is one with south facing inwards. The problem that I have now with the ESC's is that I get some unexpected behavior. I checked if the motor will run at 30 volts, so I hooked it up to a variable voltage source and increased the voltage from 12v on startup to 30 volts and it works fine when I don't try to change the speed. Only when I try to throttle down and then back up it doesn't work. And when I try to attach a 30v source directly to the ESC it won't boot up. First I tried just changing the voltage divider that checks the battery voltage, It will now boot up but not throttle up, the motor spazzes out (probably a timing issue with the ...

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    Yes, I forgot to put this in the document but you are right. I alternate the poles every time so next to one magnet that has north facing inwards there is one with south facing inwards. The problem that I have now with the ESC's is that I get some unexpected behavior. I checked if the motor will run at 30 volts, so I hooked it up to a variable voltage source and increased the voltage from 12v on startup to 30 volts and it works fine when I don't try to change the speed. Only when I try to throttle down and then back up it doesn't work. And when I try to attach a 30v source directly to the ESC it won't boot up. First I tried just changing the voltage divider that checks the battery voltage, It will now boot up but not throttle up, the motor spazzes out (probably a timing issue with the controller). So the second thing I did was change the feedback voltage divider. Now it will boot and run for a few seconds and then slow down until it stands still.

    I don't know about efficiency but the power output of the motor is way higher.

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