PBP projects for R/C models

[Kenjones1935]

I've got code that searches for "duty" that runs the motor. I have found the region that drives it backwards and that keeps it motionless. So far i have not found the forward moving pulse size, but it will not be long now.

Ken

[mackrackit]

A DC motor needs to have the polarity reversed to change the rotation???

[Kenjones1935]

Yes, DC motors need the polarity changed to change direction. I was led to believe that there is something magical in this electronic speed control that made it work differently. Thank you for reminding me to question assumptions.

Ken

[Kenjones1935]

If the electronic speed control does not reverse polarity as a function of pulse size, then I will need to use the technique Fritsl used in his wall hugging robot.

http://letsmakerobots.com/node/928

(which seems no longer available)

He cross wired the motor with multiple DPDT relay switches controlled by his PIC. I was going to copy that idea, but then I started believing the story of the magical ESC.

[mackrackit]

Hi Ken,
This may or may not be helpful, I think diagram "A" on page #3 might be to your fancy.
http://www.picbasic.co.uk/forum/atta...4&d=1228220843

[Acetronics2]

I would like to pump PWM pulses out CCP1 that have a frequency of one every 20 msec (50 per second) and a pulse width that I can (by changing the code) vary from 1 msec to 2 msec. Am I correct in guessing that the frequency of the pulses is dictated by the PAUSE command. One pulse per loop through mainloop:

CCP1 PWM @ 50 Hz ??? ... just read your Datasheet first !!!

NOW ... triggering the CCP1 module ( in compare mode ) @ 50 Hz ( from a timer ) looks much better ...

might be the PULSOUT could also do the trick for a CPU " locking time " of 2 ms ... if possible.

Now, a good program flow allows many, many things for R/C systems without using interrupts or peripherals ...

Alain

[Kenjones1935]

FATUBA manufactured the radio receiver in my RC car. It is the output of that box that I am trying to emulate coming out of my 16F887. They say here that reversing direction is done by controlling the PWM pulse size above or below 1.5ms. That is what I have been doing - I thought.

Attached is a quote from Electronic Control for DC Motors Using Discrete Bridge Circuits. It seems to say that my ESC should accept servo type PWM signals.

Is the output signal digital?

Output signals are ANALOG. Receivers vary by design on how they RECEIVE and ENCODE signals. But all deliver very similar output pulse signals, which is used to drive the servo to the desired location. This output pulse ranges from 1000uS to 2000uS, with 1500uS typically being center.
Is the output signal an on/off signal or does it have an internal regulator?

The output signal for each channel is a pulsed signal. The pulse width (commonly 1000uS to 2000uS) is determined by the corresponding channel of the transmitter. When activated by one of the proportional channels (such as elevator, aileron, throttle, rudder, or knob control) the pulse width will vary. This controls the servo movement. Most servos will be centered when the pulse is at 1500uS. Channels that are controlled by a switch (such as the gear channel) will operate the pulse width from two set values such as 1100uS when in one position and 1900uS when set to the other position to activate servo movement.
What signal does the receiver emit to differentiate forward or backward movement?

Direction of movement is determined by the direction in which the respective pulse is shifted off of center (neutral). Center being 1500uS, if the pulse is shifted above 1500uS, the direction of travel is one direction. If the pulse is shifted below 1500uS, the direction of travel is in the opposite direction.