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Author Topic: Is there a difference between a pulse coder versus quadrature encoder?  (Read 13342 times)

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Offline DNB

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Hello All,

I am strategizing the retrofit of my Enshu Accu-mill and have a question about the encoder.  The P100 from Skyko states that it needs a quadrature encoder.  My controller manual states that I have Fanuc Model 0 DC Servo motors with built in pulse coder.  Are pulse coders the same as quadrature encoders?  If not, how can I determine if they are quadrature?

Thanks,

David
Re: Is there a difference between a pulse coder versus quadrature encoder?
« Reply #1 on: February 22, 2007, 06:17:15 AM »
Pulse Coder is the Fanuc term for a quadrature encoder. Fanuc Pulse Coders are usually 2,000 or 2,500 pulses per revolution.

Darek
Re: Is there a difference between a pulse coder versus quadrature encoder?
« Reply #2 on: February 22, 2007, 07:37:05 PM »
So that means the signals are 5V A/-A, B/-B and index C/-C??  I also have a fanuc controller which may need replacing...not having to buy new encoders would be fantastic :)  Figuring out how to do spindle alignment for tool change may be a challenge though :(
Re: Is there a difference between a pulse coder versus quadrature encoder?
« Reply #3 on: February 22, 2007, 08:29:24 PM »
^^^ Correct, but the encoder cout will be too high for Mach3, 2,000 count X 4 = 8,000 counts per turn.  You can use it if the drives have a multiplier.

Offline Chip

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Re: Is there a difference between a pulse coder versus quadrature encoder?
« Reply #4 on: February 23, 2007, 02:41:47 AM »
Hi, David

It all depends on ball-screw ratio.

Not to disagree hear, but 2000 count encoders will work, may have to use 35k or 45k kernel speed on Mach to get the top speed back-up and might not archive the 300 ipm as before, speed isn't every thing.

How many turns of servo to move table one inch, I think I read another post where you stated that its a .0001 accuracy, thats a .8 inch per turn of servo / ball-screw ratio.

Lots of machines use 5 turn per inch ball-screws 200 steps per turn steppers gives them .001 accuracy, If it had a 8000 steps per turn servo I would agree.

Check your servo turns per inch, it all depends on ball-screw ratio.

Do plenty of research 

You can probably use your servo amps with +-10 volt to step / dir input cards there several out there.

Just another opinion hear.

Hope this Helps, Chip

« Last Edit: February 23, 2007, 02:45:04 AM by afn09556 »
Re: Is there a difference between a pulse coder versus quadrature encoder?
« Reply #5 on: February 23, 2007, 06:20:03 AM »
One other point to consider about the 0 model servo is the tach signal for the Velocity Unit ( Fanuc's term for servo drive.) is  generated by a F to V converter on the motherboard. By the time you built or bought a circuit to perform this you could probably just replace the Velocity Unit with a Rutex drive ( No tach signal needed.).

Which Fanuc control do you have?

Darek

Offline DNB

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Re: Is there a difference between a pulse coder versus quadrature encoder?
« Reply #6 on: February 23, 2007, 11:41:38 AM »
Hello all,

Thanks for your great input.  I am gearing up for a retrofit and am just trying to finalize the details.  I will post pics of the project as it progresses.

HillBilly: I have a Fanuc 3M-A and I believe the control unit is a honda tshushin m9 mr-20rma.  I also believe the machine and controller were built in 1981.  I see that the pulse coder goes to the control unit but I do not see anything in the wiring guide that it is passing through an F to V converter.  Is it just part of the control unit?  Also, I thought the pixie can handle this situation since it only asks for signals from a quadrature encoder.  What am I missing?

afn09556: I have a maintenance manual, connecting manual, and general use manual.  The machine manual is in storage.  Arrrgh!  As such, I do not have turns per inch data.  You are right that it has .0001 inch accuracy.  I also do not have figures on the pulse coders PPR information.  Arrrgh again!  Do you know how I can find this data without digging the manual out of storage?  Also, you mentioned I could use +-10 volt to step / dir input cards.  Do I need this?  My wiring diagram states that the pulse coder uses 5 volt.  I am researching like crazy.  Good thing is its fun!

DennisCNC:  What is a multiplier?

Thanks again.  Also, I can't help but post some pictures below.  Forgive my indulgence.

Picture of motor.  Why did the prior owner paint the motor?  I guess I'll have to scrape the paint for a view of the specs.

Picture of one of the drives

Picture of one of the current control board

Offline Chip

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Re: Is there a difference between a pulse coder versus quadrature encoder?
« Reply #7 on: February 23, 2007, 02:26:59 PM »
Hi, David

Your servo control uses the encoder to stay on track and bootstrap encoder info to the +-10 volt to step and dir cards, which interface to Mach3. Realy hard to say without the wiring Diag's Though.

I did a conversion, simmilar to yours on a Waterjet Cutter 4 axis, works Great.

Dig out the Manual's out of storage your going to need them

On the Ball-screws if you can get to one of them X or y turn it one turn measure table movement, are your servos direct-connect to ball-screws. Look's like you can turn the Y axis on front of Mill.

Where do you live?

Thanks, Chip

 
Re: Is there a difference between a pulse coder versus quadrature encoder?
« Reply #8 on: February 23, 2007, 04:55:07 PM »
In the last picture posted the 3 little black boxes labled A-PC06, in the lower center of the mother board, are the F to V converters. This is what is inside of them.

Darek

Offline DNB

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Re: Is there a difference between a pulse coder versus quadrature encoder?
« Reply #9 on: February 23, 2007, 07:03:09 PM »
Hi Guys,

Many points have been raised and I think many of these issues are addressed through the use of skyko's p100.  I will summarize my understanding below.  Please let me know where I am going wrong.

1.  Fanuc pulse coders are usually 2,000 or 2,500.  From my reading it seems that 2,000 is usually for Fanuc brush motors and 2,500 are the brushless motors that have Hall signals.  I am 95% certain my pulse coder is 2,000.  According to skyko the p100 is for 2000 count encoder Fanuc motors.

2.  Motor speed will usually be slow using a 2000 count encoder and mach 3.  However, the ball-screw ratio may improve the speed and the 35 or 45 kernel speed may need to be used.  If slow you can use a multiplier to speed things up again.  I do not have the information on the ball-screw ratio at this time.  However, the skyko  p100 comes with a step multiplier just for this purpose.

3.  The Model 0 servo uses a F to V converter to provide the tach signal for the velocity unit.  This is a frequency to volt converter?  I think the p100 can be wired directly to the encoder and it will handle any necessary conversions.  For reference I have copied the wiring diagram below.  I think it is ok to post here as this is free to download from Skyko.com.  Am I missing something?  Skyko says it needs the 5v A and B signals from the encoder and nothing else.

Additionally, Skyko says the following: "The Pixie implements a Proportional, Integral, Derivative (PID) control loop using position feedback from the motor shaft in the form of quadrature encoder signals (denoted by channel A and channel B). Each time through the loop, the Pixie calculates analog reference voltages to control the speed and direction of the motor to bring the current actual position of the motor shaft to the desired position (usually commanded by a control host through the step and direction signal lines). It does this calculation 10,000 times per second to achieve and maintain the desired position through a changing load."

4.  Regarding the need for +-10 volt to step / dir input cards to interface with Mach 3.  Skyko says, "[the p100] has a jumper selectable analog output range of ±10v or ±5v which is compatible with many commercial motor amplifiers."  Is this the function needed?

I really appreciate your input.

David