08M2 Tricycle Bot: First Test

erco

Senior Member
Today's uber-simple bot is an ugly but quite functional duckling using an 08M2. Quick prototype shown here. We're going to 3D print an improved version of this chassis to use in a robot camp. Two 9g servos, one continuous rotation drives, one steers. And a 1 PPR mechanical encoder. Easy peezy, works every time. Just have to calibrate servo turning radius to match up to a 360 degree turn with an integer multiple of my wheel circumference. In this case, 12 wheel revolutions per circle. Accelerates & decelerates. First test was this figure 8 course. Bot will soon have IR and ultrasonic sensors and audio output. Maybe light tracking too.

Video thumbnail shows bare chassis before the electronics were added. So hideous that it's beautiful.

 

Rick100

Senior Member
I like the simplicity of these tricycle bots and may have to build one. Your videos are always fun to watch. I really enjoyed the tour of your robot room.

Thanks,
Rick
 

erco

Senior Member
Finally got around to testing my idea for a simple low-tech, single I/O pin, line-following sensor on Trike bot. Two CdS (cadmium sulphide) photocells in series, making a voltage divider read by an ADC, looking down at a line illuminated by a single center mounted green LED. About as stupid simple as it gets, but it works. Lots of variables: vehicle geometry, sensor geometry (view and location), how much illumination from the LED, line width, and of course, the software.

It wouldn't be anyone's first choice for a timed line following competition, but it's about as minimal as I can think of. On an 08M2, every I/O pin counts.


Code:
servo 2, 132 ' drive servo 132stop 175fwdmax 100reversemax
b1=144' servo center position
servo 4, b1 ' steer servo center144  leftmax62  rightmax235
servopos 2, 140' drive fwd
main:
readadc 1,b0  'read photocell voltage divider
if b0<95 then let b1=b1+1 max 235  
elseif b0>120 then let b1=b1-1 min 62
endif
servopos 4,b1
pause 5 ' damps oscillation
goto main
 

techElder

Well-known member
Sadly,the collection belonged to my mother-in-law's husband who passed this last week. When I saw that trike, I couldn't help but photograph it juxtaposed with the "duck bill dipper". I knew I was going to post it here.

I have a couple of the Armatrons around; one of them with a powered parallel port interface. My son was blessed in his upbringing. Neat stuff.
 
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