Let's Make Robots!

continuous servos

For all you guys who have bought or modified a continuous 360 servo, how does it work?

 I want to be able to have a very controllable motor that I can tell to make specific number of turns and stop.  Would that be a way the continuous servo could work?

 I mean, for other servos, sending different square waves gives different angles, but if the servo goes all the way around and again...  how do you tell it what you want?

 (just want to know if it is feasible and a general sense of how it works before I buy one and try it)

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Thanks ! I'll try this when I am home.

well ... you just have to stick with chris' codes i guess, they do work for my servo:

 

75: Fast fwd

95 Wiked slow fwd

160 Crazy slow rev

175 Fast Rev

 

so you could write something like this:

turnleft:

servo 0, 75

wait 1 

servo 0, 150

 

Thanks Chris, this was exactly the kind of info I was looking for.  I think I will get some after all  (as soon as have spending money again :-P)

How would I do that? What the programing code to go with that.

well i guess you are using it to rotate the ... ultrasonic sensor right?

well why not just make it rotate at full speed and stop it some seconds later. that should do it. you know it may be slower than a normal servo but you (or we...got a continuous one too) could make something nice out of it.

So I have to buy a new standard servo because I have a continuous servo? There is no way to make a continuous servo into a standard servo?

 My little erector-set robot (with the green wheels) uses servos for drive. They came with the "Vex" kit but they are nothing more than a std. continous rotation servo. I have full fwd and rev AND speed control! Not to mention you get fwd and rev with one pin!

The command I use simply servo 1,b1 where b1 is a value between 75 and 175. If 75 is used the servo turns forward at full speed. 175 is full reverse. As you change these values (moving them closer to 150) the motors slow down. In practice it seems there is a usable range: 

75: Fast fwd

95 Wiked slow fwd

160 Crazy slow rev

175 Fast Rev

I have found that changing the value even by one is noticable. Right now the "forward" on my bot is servo 1,75 servo 2,78 -the 3 point difference is how I "trimmed" the robot to drive straight!

As for feedback, you can't count rotations. But I have been playing with encoders and I might have some ideas for you.

www.rocketbrandcustom.com baby!!

so can you just power the 360 servo with the pins on the picaxe board like a regular servo?

I was reading about the solarbotics "secret" motor driver, and they implied that you need to use an h-bridge ... 

you can use the same pins yeah. But i still can't get it to work with "servo x,y",unless i put the whole thing in a cycle, EG: 

driveservo:

servo x,y

pause 20

goto driveservo 

 

and some sort of driver will make everything easier, and by easier i mean not having the loop in your program, but still i saw some guys on this forum drive them "on the background", without having any loops, just giving one command and that's all. 

From my exp with the Parallax boebot which uses 2 CR servos for it's motor drive, they were pretty consitent. The documentation(free to download btw) tells you how to fine tune them if they are out of sync. One thing to note, these are great for flat surface use and some light terrain, but I'm not too sure about their long term use as a major motive force.