servo motor using parallel port

[abikutn]

Hello,

        I have a XY mirror scan Servo motor used for optical scanning experiment.

The question I have is:

      I already have a program to control stepper motor via parallel port. Can I use the same to control servo motor ?

Or is the SERVO motor concept different to that of a STEPPER motor ...

Thank you

[PackersFan]

Servo Motors and Stepper Motors are very different and require very different controls signals.

Check this out for more details: Motor Fundamentals

[abikutn]

Ok I understand the concept of servo to that of stepper motor is entirely different.

I just have one question: Is it possible to control a XY stage servo mirror scanner using PARALLEL PORT ?

If yes then I can go ahead and figure out how to do it.

Thank you

[NIquist]

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@abikutn wrote:

I just have one question: Is it possible to control a XY stage servo mirror scanner using PARALLEL PORT

---

  WHAT is an "XY stage servo mirror scanner"???

Are you laser scanning an OBJECT that is sitting on an XY stage?  In that case, you could control an XY stage with the parallel port but it would be a lot of work compared to buying a cheap USB or Serial control module.  Most mirror scanner servos are PID based which requires a position feedback signal and a fast servo loop so the parallel port is not an option.  You will need a servo driver designed to work with your galvo(s).

[abikutn]

Yes I am laser scanning an object and collecting the reflected light using a photodiode.

I have parallel port using to control a stepper motor XY stage. I wish to use the same parallel port to control this mirror scan too. Please help how to go by it.

[NIquist]

As I said you will need a servo driver for your galvo.  What kind of galvo are you using to scan?

[Britoa]

If you have the servo cards (and not just the motors), they most likely take in an analog voltage for command.  The parallel port outputs digital signals, which can't output analog easilly.  If you don't have the servo cards(drivers), and just the Galvos(motors), You need the drivers. 

The reason you can get away with this in the stepper world is that they require just step and direction, as logic inputs.  the parallel port has tons of those.

I would check with where you got the Galvos from, and see what they recommend to control them. 

[abikutn]

i already have a servo driver and the miror attached to the servo motors.

Cambridge technology : 6880M series mirror servo galvo scanners

Motor driver : http://www.camtech.com/products/servos/Servo%20Driver-671XX.html

Originally like you guys said, the parallel port is best used to give only digital outputs, where as the servo's need analog outputs.

Any idea how can I generate analog outputs so that I can control the servo's ?

[RavensFan]

Buy an inexpensive DAQ card.

[NIquist]

You will need a DAQ card that can generate the voltage needed to send a command signal to the 671.  The 671 will need to be tuned to the 6880 with whatever sized mirror is attached.  (If you bought the galvo and servo driver as a package it should already be tuned.)

CTI systems take in an analog command from -10 to +10 Volts.  Almost all the NI DAQ cards (and many other brands) output +/- 10 Volts so that will be easy.

Then you will need to decide how to scan your target.  A ramp pattern or triangle wave is the usual choice for scanning objects so you need to generate that in LabVIEW code along with the code that will read your sensor.  This should be done simultaneously but you really don't need a very expensive DAQ card to accomplish that.  Look on the NI website for options in your price range and do some research...

Is your system one axis (one 6880 and one 671)?  If so you will scan a raster (ramp or triangle) to measure a single line of light intensity, move the stage a tiny distance and scan another line.  When you put all the lines together into a 2D image you will have a representation of one face of your object.  Many people use a rotary stage to spin the object while scanning to assemble a 3D model of the object.  This is a bit more complex of course.