Let's Make Robots!


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Hi all,

First of all Yellow Drum Machine was my source of inspiration and after looking at all other users I have started making a Tank Servo Bot. I have just completed assembling the Tankservo bot kit from budget robotics. Currently working on assembling USB Picaxe28X1 module board (still waiting on the picaxe28x1 chip (alomost a week after ordering). My fellow robot hobbymate Duane (Octobot2) lended me one of his spare picaxe28x1 chip. Thank you Duane.

Will keep posting ...Good to join the group...

Thank you all.Atthaced is the new pic for sprocket and wheel.

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Sorry, I assumed that you were using a PICAXE.  I can't help you with Basic Stamp code because I have no experience with them.

Duane S

Wilson, North Carolina  USA

i am using PICAXE !!! :D (28x1 to be precise) that basic stamp thing is just an example of how it would work in a loop, and i can also make it work the same way with my picaxe! but i don't get how to make it work without loop.

Ill just continue not to read or understand the thread, and come with my input never the less;

Have you had a look at the Picaxe command pwmout?

i guess i'll conitune the discussion in the forums, will be much neater over there :) 

actually i never thought about using pwm for controlling the servo! thanks for the idea, i'm gonna try it tomorrow ( i am already using it for IR modulation so i know how it works, fortunately :) )

anyways i will still continue the discussion elsewhere (as already stated) because i want to understand how these folks make it work.

"But remember we are talking about continuous rotation servo" Oops, sorry ;) I have never messed with them!
I like the bot! Of some reason I want to add light-detecting.. arh, FritsLDR (embarresed to use the name myself ;) to it, it sort of has the base going I recon :)
oh btw i bought my tank threads today, but the shafts provided are way too short. Next week i'll buy the shafts set. But i am happy as i managed to stick the drive sprocket to my servo horn. :=)

i am curious about the code you'll be using to drive those servos (as far as i know they need a loop to work).

since i got a spare picaxe i could use that as a dedicated motor driver, that makes everything easier, but what are you planning to do?


It can be done as you suggest, but there is a much simpler way.

It's so simple, compared to some motor control methods.   I use the servo command to initilaize the servos in my initialization routine, and then the servopos command to control them in the program.

Once called, the servopos command operates in the background, with no loop required.

Read about the servo and servopos command in the Piacaxe Manual 2 for the basics, but they don't talk about servos for continuous rotation.

With R/C servos that have been modified for continuous rotation,  a pulse value of 150 supposedly is STOPPED.  If you want the servo to rotate CCW, you send it a command less than 150.  For example, 145 might be slow CCW.  If you want the servo to rotate CW, you send it a command greter than 150.  For example, 155 might be slow CW.

In practice, it seems that the stopped value depends all on the particular modified servo.  I've seen 4 where STOPPED turned out to be between 130 and 135.  If you're willing to work on the servo, you can correct this.  I prefer to just find where STOPPED is by a little experimentation, and adjust my speed commands from there.

Duane S

Wilson, North Carolina  USA

P.S.  I see that PSR_177 was replying at the same time that I was. 

actually i never tried servopos, and i think it's gonna be my choice since, as you just said, it works in background (that's what i was concerned about).

as for the commands, no problems with those. My servo even has a pot that i can turn so that i can get it to stop at any value. cool :)


EDIT: i still don't get it. i have also checked the manual but "servopos" still looks to me very similar to "servo". Could you post the code you are using to make your servos move? (without using a loop of course)

according to the manual "servo" should send some pulse every 20ms anyways. wouldn't that be enough? Can't understand properly ... :D