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Topic: Reverse brushless motor with ESC (Read 2 times) previous topic - next topic

Suriken

Hi!

I am trying to make a RC car with a brushless motor but I think is not possible to revert it to go back. When I arm my ESC, I set 41 as 0 and 170 as max power...

Is there a way to reverse it?

MarkT

Sensorless brushless motors are normally assumed not to need reversing.  3-phase drive means swapping wires allows initial setting of the direction.  For an application where low speed or reversing under load is needed requires either a hall-sensor BLDC or a very specialized ESC that uses inductance sensing to measure rotor position at low speeds.  The RC cars the usual technique is to use a brushed motor I believe, since starting under load isn't really possible otherwise (at RC budgets).

The problem with brushless motors without hall sensors is that the only way to establish the correct timing for commutation is to sense the back-EMF waveform on the undriven winding.  Back EMF depends on rotation speed so that at low speeds and particularly from rest there is no information available.  The ESC simply drives the windings in sequence and hopes - with little mechanical load this usually works but is a bit brittle (mechanical resonance can be an issue).  Once fast enough the feedback loop is enabled and the ESC starts working properly and robustly.

With larger motors there is room for hall sensors to accurately measure rotor position, but for most RC use (propellers) there is little need since the standard ESC doesn't require them.  Industrial brushless motors are always hall-sensor motors (because low speeds and high torque are essential features for those applications).
[ I won't respond to messages, use the forum please ]

Suriken

I think maybe it can be possible with relays. If I use 2 ESC to control both ways and a ESC to switch between go one way or the other... I have to try what happends if I disconnect ESC from arduino.

Other possibility is using 4 relay and swith between ESC to motor wires. Motor has 3 wires, one is always in the middle but the others 2 if you swith between them, you can reverse the motor. So if I switch them with relays....


Do you think it is possible?

lesto

.... just buy a ESC that support reverse ....
just type "rc car esc" in a search engine end you will find a lot of them, just be sure they have reverse and are for brushless.

i dunno how they work
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DuaneB

Hi,

Lots of hobby ESCs allow you to switch between forwards only mode and forwards and reverse modes.

check your manual you might find you have the option to enable/disable reverse

Duane B

rcarduino.blogspot.com
Read this
http://rcarduino.blogspot.com/2012/04/servo-problems-with-arduino-part-1.html
then watch this
http://rcarduino.blogspot.com/2012/04/servo-problems-part-2-demonstration.html

Rcarduino.blogspot.com

Suriken

Mine can't use reverse. I think the best option is Lesto's idea. I will check some shops to look for a cheap reverse ESC.

Thanks all!

jraskell


The RC cars the usual technique is to use a brushed motor I believe, since starting under load isn't really possible otherwise (at RC budgets).


Brushless setups are very popular in RC cars these days, and many ESCs support both forward and reverse.

lesto

a cheap and famous site is hobbyking.com, look at the comment before buy, and on rcgroup.com you will find many recension.
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