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question about analog input servo drives
« on: February 02, 2009, 03:49:07 PM »
hi everybody,
i'm new to mach3 and i am very intrested about it. i wonder, if mach3 can control servo drives with analog input,say +-10V, and if so how ?
can somebody guide me about this question.
thanks in advance.

Offline Hood

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Re: question about analog input servo drives
« Reply #1 on: February 02, 2009, 04:03:33 PM »
Not directly, Mach puts out Step/Dir  signals so you would need something to both receive encoder input from your motors and also convert the Step/Dir from Mach to analogue signals. There are one or two boards that do that, Rutex do one and I think it comes in about $400 for  3 axis. Vital Systems do the DSPMC which is a motion controller and has a plugin for Mach, that comes in around $900, it is capable of up to 6 axis if I remember correctly.
Hood
Re: question about analog input servo drives
« Reply #2 on: February 03, 2009, 10:00:46 AM »
can you explain me the signal specifications of step and dir signals please. and do you know anywhere in the web where i can find schematics to build the required boards myself.
sincerely yours.
 ??? ::)

Offline Hood

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Re: question about analog input servo drives
« Reply #3 on: February 03, 2009, 10:54:53 AM »
The pulse for step  is 5V and Mach puts out one pulse for each movement, so for instance if you need 10,000 pulses to move the motor 1 revolution Mach will put out 10,000 pulses. If you want to move 1 revolution of the motor in 1 second the 10,000 pulses would be put out in 1 second ( 10KHz), if you wanted it to do 1 revolution in 2 seconds the it would be 5KHz.
 The Direction is either High or Low and is set before the pulse is output.
Have a look in the Mach manual page 40.
Hood
Re: question about analog input servo drives
« Reply #4 on: February 04, 2009, 11:13:06 AM »
do you mean that i can use a frequency meter to convert the step pulses to analog signal to control the velocity of a DC motor and is this the way that companies like rotex are using in their breakout boards.. if this is true there may be problem for slow signals because of the delay of frequency calculations.
thx.
Re: question about analog input servo drives
« Reply #5 on: February 04, 2009, 03:07:45 PM »
Im using analog input servo drives on my setup, i used the dsp motion controller. Extremely simple to interface and gives you additional I/O. You could probably fudge something together if you're just building a machine for the sport of it. If you're looking for reliabilty and cost effectiveness in the build, just order something known to work.

Offline Hood

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Re: question about analog input servo drives
« Reply #6 on: February 04, 2009, 04:07:12 PM »
Just converting the step signal to a voltage will move your motors but you need to know where the motors are and how fast they are moving so you need feedback to the coverter boards so that it can close the loop to control them properly.
Hood
Re: question about analog input servo drives
« Reply #7 on: February 06, 2009, 07:10:45 AM »
yes exactly , there will be encoders for feedback.but as i said does the frequency counting will do the job (specially for slow steps).or there are more complexity in the breakout boards.do you have any circuit or idea for this job? if so can you please share it with me
Re: question about analog input servo drives
« Reply #8 on: February 06, 2009, 08:01:55 AM »
Here is a basic block diagram of the system.

Darek
Re: question about analog input servo drives
« Reply #9 on: February 07, 2009, 10:42:56 AM »
thanks everybody,
dear hillboy is this the diagram of a brekaout board which had worked in a real machine.if so can you introduce me the source site for that.
thanks