Thread: Need Sproggy Servo Schematic and Code

Just wondering...does it have to be sproggy?

Ill assume you wanna use it for screen or amp tray?

Theres lots of servo controller out there. Do you want to use a stepper motor or just plain? For sensing position you can just add some sensors that start and stop the motor.


This might help you out :

http://www.mp3car.com/vbulletin/show...2949#post32949

Well, if I remember correctly, the sproggy had provisions to enable the PIC controler to remember the motor position, and be field programed, int he sense that you could put it into some sort of program mode, and control the servos manually, get to the position you want, and save the information in the pic.

I have been doing some research on the net about motor control, but have yet to see one that incorporates that feature. I would like to see the code Sproggy used, so that I can try and figure out how he enable that. I am also interested in attempting to change the code to apply to stepper motors, although I have yet to figure out if that is possible.

I have seen the link you posted before, and I believe I have created a design that will meet my needs, and quite possible the needs of other people, I am just trying to complete it. Once it has been tested, I will post my design for all to see.

Till then, I am still researching.

Thanx
Michael

Cool...

How confident are you in writing your own PIC code? Because you can rip some sample code from microchip website and integrate them on your design.

Im using the L298 dual full-bridge to control 2 motors for a project. It can also drive a stepper motor. Be warned though...this chip as a bit fragile so make sure you follow the design recomendation.

http://www.st.com/stonline/books/pdf/docs/1773.pdf

With the sproggy, Ill like to see the design too...it sound interesting. But how does it sense the current position? It will most likely need some real position feedback, some just use some kind of a timer (bad design)

Let me know when you find it

Well, since the stepper moves in steps, I would assume that the steps can be counted, and then used in the code to remember the position.

The sproggy position is determined by the servo. All servos have a variable resistor that changes resistance in relation to position. So, assuming fully left is zero, and fully right is 20 ohm, the servo controler measures the resistance of the variable resistor, and remembers it. When the servo needs to move to that position, it provides the PWM required, until it reaches the desired resistance, and then stops, or, since a servo is uses Pulse Width Modulation for movement, you can record the pulse width, to get you to the same location, although the resistor feedback I believe is the prefered way.

The problem with servos is that, unless modified, they have a limited range of motion. If modified, you generally love the variable resistor, there by losing position control.

That is why I think the stepper might be a better alternative.

From what I have read, the ULN2803 is the prefered chip for Stepper motor control when using a pic or stamp. http://www.jochenlueg.freeuk.com/interface/stepper.htm

Thanx
Michael

Opps my mistake the "servo" bit disappeard in my head

The L298 outputs can handle up to 2A each, ULN2803 is only upto 0.5A. Well I guess it all depend how much current you wanna use up. I just kept getting an impression you gonna use your project to move some heavy item. You can also add the L297 to control the L298, this make your interfacing easier.

Yes you can count the number of step on the stepper motor as long as you dont overload it. Since its open loop...theres no fedback of how far it has stepped and can easily lose track of its current position. You still need to somehow let the contoller know where the postion is...even just the start and stop position maybe good enough.

Hi,

Cool deal, thanx for the info.

Michael

I have sproggy servo controller for sale at www.mastero.tk has two versions single and double servo versions.

Contact me for the price. The price on the site is outdated.


cant upload the files if you want them mail me ......

cheers
Mastero

Wiredwrx,

Heres another idea :

You can just use a standard motor, each "gear" revolution is sensed by a reed switch or hall effect. Lets say each revolution = 1mm of actuator movement.

The output of the reed switch is then fed to the controller. The controller keep count of the pulse...tracking the position. If the pulse dont arrive then you know the motor has stalled and an error can be generated from there.

This is infact a typical satellite dish motor controller