SERVO THROTTLE SIGNAL

[Kain]

Wow, it's been a while since I visited the forum  ;D, but anyways. I got my hands on a brushless DC motor as well as the controller for it and I wanted to use it for a non-RC model applications, so obviously in order to drive it I will need to emulate the same signal as the one a receiver is feeding to the motor control. I did some reading and what I figured is that the throttle signal is a pulse with anywhere between 1 to 2ms length and repeated usually every 20ms, in other words - it is a PWM that the servo is looking for. Now I am not RC maniac for now so if somebody is more experienced with this stuff can you tell me if the speed/direction is controlled by the pulse width only? Also are the motor controls looking for any other sequence besides the PWM signal? Any help is appreciated. By the way - I did a simple PWM setup with PIC which provides pulse width between about 1 to 2ms adjustable and repeats every 20ms. It consists of only 4 parts so if people are interested it can be added to the project section since it is as simple as it gets.  Anyways, hope to get some answers on the question above. I know that Audioguru has always something to say (this is in a good way btw  ;D).

 

[audioguru2]

Ho Kain,
Model aircraft, cars and boats use PWM to control their motor's speed in an ESC circuit.
A pulse width of 1ms imakes the motor stop or run very slow. A pulse width of 2ms makes it run very fast.

 

[Kain]

Nice, but then how does one reverse direction?

 

[audioguru2]

Nice, but then how does one reverse direction?

Reverse the connections to the motor with a relay.
I have seen many model airplanes and cars, but I have never seen one go backwards.

 

[Kain]

Um, reverse the connections? We are talking about brushless motor not brushed... I don't think this will have any effect on the direction of rotation. Maybe it's a software adjustment or something...

 

[Ldanielrosa1]

I'm not all here right now, but it looked like you were asking about the "throttle" control on an engine carburetor.  Reversing direction would be the transmission?

If the "throttle" is actually for an electric motor, there is no guarantee that the servo standard applies- but assuming it does there are a great number of possibilities, which I dare not list for fear of making a fool of myself (which I may already have).

 

[Kain]

I figured it out. The trottle signal is only for speed control purposes. The motors normally spins in one direction only. Thus, if we want it working in reverse direction, the motor control has to be programmed with the corresponding instruction. Either way - it cannot be done on the fly with most RC brushless motor controls. Thanks for the help anyways. 

 

[CPW]

Maybe this is a little late since you seem to have already figured out what you want to know, but maybe I can help you a little bit.

This does not apply to airplanes, since airplanes don't go backwards, but many electric radio controlled cars do go backwards. I am unsure if this applies to ones with brushless motors, but I don't see why not.

In RC cars with motors that do go backwards, a pulse of 1ms usually means full speed in reverse. 1.5ms (or 1500 microseconds) means stop, and 2ms means full speed forward. However, in a car without reverse, audioguru was right. 1ms would be stopped or really slow, and 2ms would be full speed.

Hope this helped you, at least a little bit.  ;D