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Topic: Turning a motor into a servo (Read 2 times) previous topic - next topic

Fons1302

@ zoomkat: Why would that be? It has to turn 90°left/right and about 60° down/up. It must be fast so it will have to be powered by larger motors. But for a start I can make some limitations!

zoomkat

Quote
I don't know why I tried servo's first but I am not sure if servo's can make precise angle reproduction... it follows your pots' movement very well but can you make it move 59,5 degrees if your turn your pot 59,5 degrees??


If you are looking for smooth .5 deg control resolution using your head, I doubt it will happen. I made a simple joystick control for my servo based webcam pan/tilt and learned a lot. You could get a pair of plastic safety glasses and attach a laser pointer to see how well you can make the laser dot stay on target. What do you do if you need to move your head without moving the cam? If you manage that, how do you get the cam and head controller back in sync? I'd do some simple proof of concept testing before starting to invest serious $$$.
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

fliggygeek

If you are looking for fast .5 degree resolution control, servos arent what you need, you can find some good sized stepper motors that with a 2-1 gear ratio will give you incredibly fast speed and .5 degree or better resolution. these are what they use for CNC mills so you can be sure they're the best option.
"Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent di

Fons1302

#8
Feb 14, 2011, 01:05 pm Last Edit: Feb 14, 2011, 02:14 pm by Fons1302 Reason: 1

If you are looking for smooth .5 deg control resolution using your head, I doubt it will happen. I made a simple joystick control for my servo based webcam pan/tilt and learned a lot. You could get a pair of plastic safety glasses and attach a laser pointer to see how well you can make the laser dot stay on target. What do you do if you need to move your head without moving the cam? If you manage that, how do you get the cam and head controller back in sync? I'd do some simple proof of concept testing before starting to invest serious $$$.


I guess reaching 0.5° precision is hard if you got a tight budget and maybe it is too precise too but with stepper motors (like fliggygeek proposes) it must work. Thanks for letting me realize it. The problem if you want to turn your head without the camera's is not an issue with my project. It goes into a larger project where you are stuck into a suit that allows you to control a humanoid from far away  :). The person in the suit has video glasses that show both camera's of the robot (giving you 3D sense). Moving your head will give you the feeling of being in the robot's position. I know it is too big for me to start but that is why I just will start with the head control part. And dreaming doesn't hurt!


If you are looking for fast .5 degree resolution control, servos arent what you need, you can find some good sized stepper motors that with a 2-1 gear ratio will give you incredibly fast speed and .5 degree or better resolution. these are what they use for CNC mills so you can be sure they're the best option.


I never stood still with the possibility of using stepper motors because I thought using DC motors was the way to walk. Got to check them out, thanks. But I hope I can use my DC motors for something else or for a proof of concept setup. But I need absolute position sensing so I must still use a pot or make some memory/preset function.

jackrae

To interpret head movement why not use a 3-axis accelerometer chip.  This will give you the required three degrees of rotation.
jack

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