View Full Version : Toggle between radio control and autonomous control

11-16-2009, 10:33 AM
I am new to Parallax. It comes highly recommended.

I wish to build a 1/10 scale hobby level radio control car that can also run autonomously. I think the Basic Stamp can do the job, but I am not sure. The question is how do deal with the pulse width modulated signals that come from the radio receiver. Presently they go directly into the electronic speed control module and the steering servo. I thought that for my design I could use them as inputs to the PIC.

I hope that I do not have to use Basic Stamp code space and compute power to continuously sample the three RC receive channels. Is there some kind of transition detector which can digitize the PWM signals? I assume the PIC input can figure when they change.

If the Basic Stamp can not be the central brains of this operation I can use double pole double throw switches under PC control to steer the PWM signals. I would rather not go that route.


Mike Green
11-16-2009, 11:18 AM
There is no mechanism for the Stamp to automatically sample the RC channels. Typically you'd use a sequence of 3 PULSIN statements, one for each channel. The RC receiver normally receives one channel at a time and the PWM signals occur in sequence and repeat about 50 times a second. There's not much time left to do control functions once you account for timing 3 RC receive channels and 3 servo PWM output channels. It's possible to offload the PWM output functions, but I don't know any ready-to-go PWM input processor.

I would strongly suggest you look at the Propeller. It can easily do the RC receiver timing and the servo PWM generation with two cogs (processors) and have plenty of processing power to do whatever control functions you need. The Propeller Servo Controller is a compact board that comes pre-programmed with a 16 channel servo controller, but the outputs can also be used as inputs by modifying the control program.

11-16-2009, 10:39 PM
Thank you, Mike,

That is just the information I was looking for. Propeller it is.


Scott Portocarrero
11-17-2009, 02:05 AM
Hi Ken

I have a similar project that works perfectly. I am using a 7 channel receiver and a JR 9303. Basically the robot runs autonomously until I select what I call the program select switch (lets call this AUX2) When it is in the 1 Position the robot is autonomous and when it is in the 0 Position I can control the robot via remote. The only difference between your application and mine is that I am using differential steering (tank steering) and you are using a different set of wheels to steer. Attached is my program if you would like to look at it.

I ran everything out of my receiver into my BS2. The BS2 does all the processing and the radio does the mixing for the steering (which you do not need!)

Feel free to contact me with any questions

Check out this thread:


11-17-2009, 09:10 PM
Oh, yes, I forgot yesterday. I need the sensor system.

I'm thinking the easiest competition would be for the BOT to look for a light bulb that is placed at floor level in the exit. What Parallax sensor would do this?

TSL1401 Linescan Imaging Sensor Daughterboard $50.00 ?