How encoder strips help us???

[patriciooholegu]

Hey people.
Since a few days there is a question in my mind. The encoder strip you find on home printers, turning simple dc motors into servo sistems...There is a way of taking something like that to convert a powerfull ac motor with gear reduction into expensive servo? I have one 110 vac motor, removed from a copier machine, with 2 revolution per second and enough torque for moving a small go-kart from my son... with my on it.
If it is posible using long enconder strip from some big plotter machine or something like that, or better, home making one with standard kodak photo film stock (In that part i have no idea how to make it...) it will be awesome.
But from something i have to start:
How to they work? Does anyone now?
I´m sorry about my inglish...

[bborb]

The DC motor is reversible by polarity,allowing it to hold a position against forces and allowing braking. The 110vac motor is not reversible...... or is it?

[patriciooholegu]

Originally Posted by bborb The DC motor is reversible by polarity,allowing it to hold a position against forces and allowing braking. The 110vac motor is not reversible...... or is it?

This motor i have (vac 110 motor) have reversible option, by a simple circuit i plan to make. one`s i finish it i will put it on cnczone.com.
The main problem is understand how to make, or savage some encoding strip, but first i have to now more about them.
They are using cuadrative or pwm signals?? for example...

[Al_The_Man]

If the motor is a 1phase/split phase motor, then you will have to reverse the start windings for reverse direction, this type of motor will have a capacitor feeding the start winding.
They do not however, make even close servo motors.
In some cases, a synchronous motor is used that resembles a stepper motor, but runs off 110vac, on these you could theoretically change the frequency for speed control.
The encoder strips usually use the same method as a rotary quadrature encoder, two detected pulses 90deg spaced.
Al.

[bborb]

The encoder strip is a plastic timing fence that looks clear at first glance, but has black lines painted on it. The strip is threaded through an optical sensor on the back of the carriage.

[Al_The_Man]

Here is an excellent reference for sensors, it includes explaining (partly) the Moirè
effect to obtain the high resolution on photo-cell detected encoders.
http://claymore.engineer.gvsu.edu/~j.../cont_sens.pdf
Al.

[Mike Everman]

US Digital has the strip in lengths up to 34", with 500 counts per inch of resolution, $74. They have the read-heads too, if memory serves, those are about $30.
http://www.usdigital.com/products/en...al/linear/lin/

[patriciooholegu]

Originally Posted by Mike Everman US Digital has the strip in lengths up to 34", with 500 counts per inch of resolution, $74. They have the read-heads too, if memory serves, those are about $30. http://www.usdigital.com/products/en...al/linear/lin/

Ok, there is a picture of the motor i have. It is not the same, but very close:
http://www.cnczone.com/gallery/showp...0/ppuser/70552
It is working with capacitors and may be not good for servo, but i want to try at list.
remember that the main question now is about encoder strips. Im waiting for one answer on www.mercadolibre.com.ar to see for long encoder strips savaged from plotter machines. but the best goal should be to make it diy, and i´m breaking my head to see the way of doing that.
Thanks so far for the replies and keep it moving!!

[Al_The_Man]

That is a small split phase induction motor, you would need to bring both ends of the start winding out in order to reverse it, it appears just to be set up for one direction.
No good for servo operation, I'm afraid.
Al.

[bborb]

Picture a dragstrip where cars drag race. Now build a picket fence the length of the dragstrip, right in the middle between the two lanes of the dragstrip. The slats of the picket fence are 6inches wide and placed 6inches apart. Now you and a buddy are racing, at night, and your cars are equally fast so you are neck and neck the whole way. Here's where your question comes into play. During the race, you shine a flashlight at the picket fence and on the other side your buddy observes what appears to be a light that is flashing very fast. Now your buddy is Superman and he can count very fast, and he can count the flashes of light and compute at any moment how far he's travelled since you turned on the flashlight.
The encoder strip is the picket fence, and you and your buddy are "Team Reader Head"...... you being an LED and Superman is an opto-sensor which turns on and off 5volts, ON when light hits it and OFF when light is blocked.

[patriciooholegu]

Originally Posted by bborb Picture a dragstrip where cars drag race. Now build a picket fence the length of the dragstrip, right in the middle between the two lanes of the dragstrip. The slats of the picket fence are 6inches wide and placed 6inches apart. Now you and a buddy are racing, at night, and your cars are equally fast so you are neck and neck the whole way. Here's where your question comes into play. During the race, you shine a flashlight at the picket fence and on the other side your buddy observes what appears to be a light that is flashing very fast. Now your buddy is Superman and he can count very fast, and he can count the flashes of light and compute at any moment how far he's travelled since you turned on the flashlight. The encoder strip is the picket fence, and you and your buddy are "Team Reader Head"...... you being an LED and Superman is an opto-sensor which turns on and off 5volts, ON when light hits it and OFF when light is blocked.

Even a dumy undestand that explanation.. Thanks man!!
But sometingh i didnt have clear is this:
The slats are, from beguining to end, 6 inches wide and apart? So the feedbach reduces just to confirm movement and that movement is of 6 inches.
Wath about slats 6 inches wide but 6.1,6.2,6.3,6.4...inches APART, to feedback not only position and movement, also THE EXACT PART OF THE DRAGSTRIP WERE YOU ARE LOCATED (Called pulse weigh modulation??).
Now this is beyon encoder strips, but it is a question i have. (I was studing stepper motors the last months, so my main experience are with this...).
Oh! another thin:
on a servo system, that pulses (The light´s my frend count and compute) only are send to the controller board, or are send to te computer and the computer do wath it considers the best?
I read about the EMC software for linux, witch is able to accept IN pulses from servo feedback and do with them wath she wants (So...Wath i want)