position sensing

[iceberg25]

hi!it's me again.
i just recieve a task that want our to create a moving disk that it will automatic move and it woun't be out to the area that we had fixed.
Now i am facing such a big problem is how to programe the pic,we are using the pic16F877 to control it.
Guys~who has any idea want to contribute to me?
thanks~

 

[blueroomelectronics]

Nope, I have no idea what you want. What sort of disk? What area?

 

[Gayan Soyza]

I think he is having a positioning problem.The disk has to be stop in certain pre programmed places.

One of my friend did a similar project recently.He used IR LEDs as transmitting sensors.

To do without sensors you need to know the correct timings of the belt or what ever the disk is moving.

 

[jpanhalt]

Isn't that interpretation of the OP's question like similar problems faced with CNC machines for which there are two common solutions:
1) A servo/feedback method
2) A stepper motor

Personally, I prefer the former, but if the system design is good, the stepper solution seems to work well too.

Since the OP is talking about PIC control, perhaps s/he show look up stepper motors as the easiest solution.

John

 

[Leftyretro]

Isn't that interpretation of the OP's question like similar problems faced with CNC machines for which there are two common solutions:
1) A servo/feedback method
2) A stepper motor

Personally, I prefer the former, but if the system design is good, the stepper solution seems to work well too.

Since the OP is talking about PIC control, perhaps s/he show look up stepper motors as the easiest solution.

John

Stepper solution would be open loop Vs closed loop for a feedback sensor method. While the stepper sounds simpler, it still needs some kind of fixed reference sensor at start-up and software to search for the starting point.

Lefty

 

[Ubergeek63]

Well knowing absolutely nothing about your application, since you provided no details, I will assume that you just have rotating a disk and will propose the easiest thing for it and suggest dumping the PIC.

**broken link removed**

At the end of the sheet, figure 15, shows controller logic that would even work for the line followers everyone seems to love. Add a clock, and a little logic with optical sensor to drive the direction pin and you have steering control for a stepper.

If you want it to stop just stop the clock. A lot can be accomplished with simple means and no programming. An single ST driver chip instead the two TI ones along with a little logic will accomplish a lot.

A different type of follower would be two wheels driven by steppers and simply slow one of the wheels to turn.

The simplicity is wonderful and makes it much easier for anyone not interested in programming.