position sensing - Electronic Circuits Projects Diagrams Free

iceberg25 · 9th May 2008, 03:56 AM

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 · 9th May 2008, 04:02 AM

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

Gayan Soyza · 9th May 2008, 10:52 AM

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 · 9th May 2008, 04:25 PM

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 · 9th May 2008, 08:34 PM

Quote:

Originally Posted by 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

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 · 10th May 2008, 01:00 AM

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.

http://www-s.ti.com/sc/psheets/slus369/slus369.pdf

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.

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9th May 2008, 03:56 AM
iceberg25 New Member	position sensing 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~

9th May 2008, 04:02 AM
blueroomelectronics Experienced Member	Nope, I have no idea what you want. What sort of disk? What area? __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

9th May 2008, 10:52 AM
Gayan Soyza Experienced Member	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. __________________ Gayan Forum Supporter

9th May 2008, 04:25 PM
jpanhalt Experienced Member	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

10th May 2008, 01:00 AM
Ubergeek63 Experienced Member	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. http://www-s.ti.com/sc/psheets/slus369/slus369.pdf 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.