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Picaxe bldc ESC Driver

Hello guys!

I'm brand new to letsmakerobots and newbie of picaxe world...so forgive me for the noob question.

I’m working on a project that involves controlling a brushless ESC (with reverse option) with a microcontroller instead of the R/C receiver. Essentially I need to be able to run the motor in both directions alternatively, at preprogrammed speed, using 2 switches eg. Start run in CW and start run in CCW.

Basically what's shown in the video is what I need.

Is a project that can be implemented using Picaxe? I know that Picaxe 08M has 2 Pwm outputs; they can be used as Pwm generator to drive the ESC input?

Any help would be greatly appreciated

Thank you in advance,

Max

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A typically radio control transmitter/receiver supplies pulses to the servos/ESC at approximately a 20 Hz rate or one pulse every 50 mS. For safety reasons, upon initial power-up, the ESC will not arm until it begins receiving pulses of approximately 1 mS width (lowest throttle setting=motor off). This is to prevent someone from being injured by turning on their transmitter with a throttle setting that would cause the motor to run instantly. On some model aircraft the propeller can cause serious bodily injury if this should occur when a hand or other body part is in close proximity.

As far as reversing the motor direction is concerned. Although many of the ESCs are somewhat user configurable for things like battery type, voltage cutoff and motor braking among other things. The ones that I have used in the past (Turnigy Basic, Turnigy Plush, Exceed and Castle Creations) do not have a reverse mode. To reverse the motor direction requires switching any two of the three phases going from the ESC to the Brushless Motor (the red, black, and yellow wires in the video). I am in no way an expert of these things, my experience with the ESCs comes from years of building and flying model airplanes. This does not mean that ESCs designed for cars could not have a reverse mode (I have no experience with these ESCs). But the one shown in the video is one of the type that I have used before.

 

Car esc's almost always have reverse modes.

Many car ones apparently don't have arming, but do have 1 time calibration routines when I asked in a local hobby shop. The ones that do have arming tend to be hold throttle in reverse (which would be minimum for aircraft) for a second, wait for a beep, set throttle to zero (or aircraft 50%). 

 

Otherwise driving the car ones is very much like driving a continuous rotate servo. Heck, can probably reuse the code for that just fine.

 

 

Turnigy, exceed and castle do ground esc's too.

 

I think its boats where its a bit more confusing. Some guys use ground esc's, some use aircraft.

Thanks for correcting me on that 6677. I will have to see about getting my hands on a ground ESC and do a little experimentation of my own.

Also, I got my numbers reversed in my above comments. A typical RC transmitter/receiver send pulses at 50hz rate or one pulse every 20 ms. Sorry about that!

Thank you for your aswer birdmun!

After a google search I've found this advice...To arm the ESC you need to provide 1ms wide pulses, which equates to minimum speed (2ms equates to maximum speed). The number of required pulses is unknown, but I’d suggest 10 to 50 pulses should work. 

That said, you should be able to drive an ESC with a PICAXE. I have seen a few times here that ESCs may have an arming sequence that needs to be performed everytime they are powered up. If so, you will need to find out what sequence would be required for your preferred ESC.