PBP projects for R/C models

[Kenjones1935]

I'll catch you all up a bit.

I have changed tack.

I am trying to go from a hobby level car with PWM controls to a toy level car most of which have simple DC wheel and servo controls. The purpose is to reduce the cost of kitting for school students. In addition to reducing the cost, DC control of two wheel drive makes it easier to implement a sporty racing-like skid steering.

I purchased (at K-MART) two 1/10 scale toy cars on sale each for $25.95. Their original prices were $50. The 1/10 size gives me more room for adding microchip electronics. The wheels and the steering if driven simply by DC with reversing current are easily controlled using DPDT relays controlled via current drivers by my PIC .

WRONG! The steering servo contains both a DC motor and an angle measuring device which is read by the electronics that comes with the car. A total of six wires go to this servo. Where can I read how this works? Should I just go back to the store and buy 'proper' toy level cars? Your suggestions would be greatly appreciated.

Thank you thank you for the oscilloscope. Without it I would not have the faintest.

Ken

[mackrackit]

A total of six wires go to this servo.

That sounds like a stepper.
A picture of the setup might help...

[Kenjones1935]

Toggling between autonomous control and radio control is much more complicated for the toy level car than for the hobby level car. Why? Toy level drives the steering servo and the wheel motor each with DC in both directions. This requires four wires. There is no common ground. Hobby level cars use pulse width modulation signals for these two jobs. Only two wires are required. The grounds are common.

Toggling between PIC and R/C in toy level requires switching eight wires - four from the radio receiver and four from the PIC. The same operation on PWM wires requires switching only two wires.

Hmmmmm...... That's a pretty good argument for sticking to the expensive machines.

Ken

[Kenjones1935]

I have some Radio Shack solderless prototyping boards. With 22 guage solid wire I can create a fairly robust kit. I need to connect ten signal wires from the PICkit 2 to the solderless board. The Digi-Key S5752-12-ND header might work. The question is whether 22 gauge solid wire will fit and stay in this device. If not #22, then what gauge will work? Or is there a crimp-on male connector that will do the job.

What did the Microchip engineers have in mind when they designed the PICkit 2 printed circuit board? Any ideas?

Ken

[mackrackit]

22 gauge will be snug and if you do your breadboarding like Darrel does it all should stay put.
http://www.picbasic.co.uk/forum/atta...2&d=1278267329

[ScaleRobotics]

What did the Microchip engineers have in mind when they designed the PICkit 2 printed circuit board? Any ideas?

A compact USB device that programs all their MCU's, using 5 to 6 connections?

But what do you mean Ken?

On a tangent, here is what they were thinking for the pickit3:

[mackrackit]

A compact USB device that programs all their MCU's, using 5 to 6 connections?

I think Ken was getting at the 44 pin dev board. It is kind of useless... Mine got the most use helping Ken get started. It is back to collecting dust.

[Kenjones1935]

This describes what I found when I took the "servo" apart. (I got it back together with much struggling so this is from memory.)

It has 2 wires that go to the motor and 4 wires that go to some kind of rotating position sensor. On a small board are 2 etched concentric circles which are in contact with a 4-pronged device mated to the spinning gear. I think 2 of
the 4 prongs touch the outer circle, the other two the inner circle.

Have any of you come across such a device? Any idea its purpose and how I control it. Other cheap cars just go bang bang into the steering motor with a little spring plus the caster effect to bring it back to neutral.

Ken