Brushless motor clockwise &anticlockwise control

Hi,guys, I am using a mega 2560and a brushless motor a2212 and an esc … Is there any one know how to use servo to let I rotate with clockwise and anti-clockwise? I just find that I can only change the speed but cannot change direction…

How would you expect to use a servo to change direction ? I guess you could use the servo to drive a gearshift lever, but that is not a practical solution.

Two suggestions: get an ESC which allows you to run the motor both ways.

If you swap two of the three wires from the esc to the motor, then the motor will run the other way, assuming it is the normal three phase type of brushless motor. There are various possible arrangements of relays or digital relays you could implement to accomplish that.

RC ESCs for sensorless BLDCs don't support reversal (they cannot run very slow so cannot reverse, since the backEMF falls into the noise at low speeds, and the backEMF is required for commutation.)

In theory you could have an ESC that could be started in either direction, but not under any sort of load (remember these motors drive propellers only). ESCs start a sensorless BLDC with open-loop drive which has no stability or power available and switch to closed-loop control once the backEMF is large enough.

For reverse you either need a brushed motor and its ESC or a hall-sensor BLDC and ESC that uses halls for commutation (these are used for RC wheeled vehicles for instance).

MarkT:
RC ESCs for sensorless BLDCs don’t support reversal (they cannot run very slow so
cannot reverse, since the backEMF falls into the noise at low speeds, and the
backEMF is required for commutation.)

In theory you could have an ESC that could be started in either direction, but
not under any sort of load (remember these motors drive propellers only). ESCs
start a sensorless BLDC with open-loop drive which has no stability or power
available and switch to closed-loop control once the backEMF is large enough.

For reverse you either need a brushed motor and its ESC or a hall-sensor BLDC
and ESC that uses halls for commutation (these are used for RC wheeled vehicles
for instance).

Mark, I do believe that there are brushless ESC controllers that do allow for reverse/forward commands as used in R/C car models. While I haven’t personally used such, just single direction airplane ESC.

I suspect that ESC is using open loop control to start in reverse, but won’t handle
direction change under load, which is what you need for a servomotor (as opposed
to an RC model car on the level). They probably do some extra signal conditioning
to pick backEMF signal out from the switching noise to help extend the speed range
it handles.

If you want to do the job properly hall sensors are the answer though. I’ve even modified
a largish outrunner with hall switches (tight squeeze), and it sort of works (the positioning
is hard to get right in a 7 pole-pair motor!).

I’ve some proper brushless servomotors that were a bargain off eBay, hall sensors and
200W rating (24V 8.3A) and driving them properly means complete independent
control of speed and torque, can do regenerative braking :slight_smile:

Just bought my son a HSP car with brushless motor, which uses this ESC : http://www.ebay.com.au/itm/221239062591

That ESC is programmable, and supports reverse. To do this, you program the ESC to three points on the transmitter throttle range, neutral (stopped), full forward, and full reverse. So I guess that action is telling the ESC at what point in the receiver output represents neutral, and hence anything more is interpreted as forward, and anything less is interpreted as forward etc.

Reverse can be applied while moving forward, as it's also used for braking.

HTH

Cheers, John