View Full Version : connecting ac drive to computer

j king
09-30-2009, 04:25 PM
I am at a standstill. I can figure out how to connect the ac drive to the BOB to run off Mach 3. Here is my post on the 'other' board.


It shows the terminal strip. The link in the post shows the manual. It is too much for me to do I think. It talks about comunication ports or something. Is there a simple way to connect the drive to the bob?

Here is a suggestion from JST on the prac. board.,..

"If you have a computer sitting there, and no interface, you will either have to get an interface and suitable device driver, or use the RS422/485 connection, which is a serial communication system similar to the connection to your printer etc. I'd suggest RS485, it is very standard."

I may have to dump this drive and get an simpler one but thought I would ask here to see if there is a way. Thanks as always! Jim

Here is the manual.. link...

09-30-2009, 06:01 PM
Have you looked at the installation/setup documentation and/or asked your question at www.machsupport.com ?

10-01-2009, 01:04 AM
To hook a VFD to a computer you need a step/dir or pwm to analog interface. Serial RS-422 interfaces will not work with Mach3.

My favorites are made by Peter Homann:


That one will do. I would get the version with the built in DC/Dc converter.

Set up Step and Direction lines from the computer to the board. Configure Mach as in the instructions. The analog output of the board goes to FR (+) and FC (-), the built in relay go to S1 (Relay NC) S2 (Relay NO) and SC goes to relay common.

Drive should be set to NPN inputs as in the manual. #2 on the SW2 dip switch should be set to voltage input.

Set parameter n001 to 10, this should set it to 2 wire mode. Set Parameter n004 to 2, this makes it accept a 0-10v analog signal to control the motor.

Set the rest of the parameters to match your motor.

10-01-2009, 04:28 AM
In your drive manual, look up pulse follower mode..

it is a 5 volt pulse train that dictates speed to inverter.

Sorry, am about half blind tonight or I'd read the other post.. if you have tried this? well there is always a summer.. it takes pulses and makes a 0-5 volt output. I did have several of these gadgets laying about, look like a relay, but have some kinda amplifier in them.

Ohh.. 90% time of the drives come, the com port is not there.. ok? they all have computers, cpu's in them.. but no real way or program written inside them to LOOK OUTSIDE for communications.. the lil cpu runs comparisons and checks waveforms, a lot of math. and Stopping once a cycle to "time" a communication from outside disrupts the loops.. Mostly the comm hardware that is not there is a buffer area where the com is stored till the computer complete's a cycle..
Talking to them lil basic stamps years ago? well.. you'd have to smack it, get it's attention.. I used a pin interupt, but then the program that is running would cease till the communication was over..

ABB, well they came up with a machine builders dream.. a data highway board where you could just link the drives together and read-dump information into them from a serial cable. Saved about a dozen wires on each drive to connect, and had options like current monitoring from control room and speed, and fault.. all kinda neato things besides just on and off... THEY are high dollar and mostly out of :our price range. Just wiring up a console, instead of thousands of terminations and drilling and installing buttons and switches, meters.. just program them into a d-tam.. off and away.. changes? sit in a nice air conditioned office instead of standing on your head in a console with hot wires all around you to bump or knock loose.

J Tiers
10-01-2009, 08:56 AM
Most all drives will take an analog voltage input to set speed. That is what the manual potentiometer does, but the voltage can be from any source that will produce one within the range. Usually there are parameters to set the input range and type of signal.

The most common may be 0 to 10V, but -10 to +10V, and the "4 to 20 ma" type signal are often also allowed

The pulses mentioned may refer to a "PWM" signal which sets the voltage (and speed) by controlling the width of pulses. it amounts to the same thing as an analog voltage input.

Many drives have provision for a serial link also. The most common hardware type is RS485, but the "protocol", or structure of the data , may be very specific to the manufacturer.

The question is how to link up the specific machine control (in your case mach 3) to the drive. Most likely some sort of adapter is required, unless the program runs on special purpose hardware that already has an analog output, for instance.

Changing drives is not necessarily going to make a difference. The drives market is competitive, and most drives will do what the other drives all do, and have similar inputs. They all try to get installed in place of another manufacturer, which means they have to do what the other guys did, at least.

Drives are almost a commodity, and most interfaces are going to fit the lowest common demominator.

A manufacturer may ADD a useful type of input, but it is rare to find a drive that lacks inputs that the other drives in it's "class" have. Any manufacturer that does that without a much lower cost, will not get installed much. But any one that can get it's "special" input used, may be able to "lock out" all the others. Eventually that input will be copied, if it is useful.

So a different drive won't be likely to offer a magic solution. The manual might be better, though.

j king
10-01-2009, 10:08 AM
Good news! Bro inlaw is an electrical engineer.Currently laid off. Gave him a call and he is coming to take a look at what I have.

Happy dance ~`~`~

10-01-2009, 10:48 AM
I use one of these spindle speed controllers along with mach3 and my VFD.

At the bottom of that page are several easy to understand wiring diagrams for various systems.

I'm a real knuckle head when it comes to electronics, but I found hooking this setup very easy with the provided fine instructions.

10-01-2009, 05:22 PM
4-20 ma is the most common feed back loop control out there. You can find plenty of I/O combination boards out there that will interface just fine with Mach3 systems and your drive

j king
10-01-2009, 06:12 PM
thanks for all your help guys!

10-02-2009, 01:26 AM
4-20ma is common but for motor drives 0-10v is the most common, though this drive the OP has will do 0-10v, 4-20ma, and 0-20ma. I dont think I have ever seen a VFD that has -10-0-+10 input though.

Omron VFDs and Servos are usually Relabeled Yaskawa Drives. Good drives.

I really recommend the Homann Designs one. It has LED feedback so you know whats going on. It really helps troubleshooting. Plus the guy has really helped me out with things in the past like my tool changer on the Hercus.

One thing that you can do when you get the spindle controlled by Mach is to add a spindle sensor and you can close the loop. That is Mach will monitor the speed of the spindle and if is sees it slow down it will kick up the drive to compensate. I have this on my milling machine and it really comes in handy when you get a decent load on the machine, especially at lower RPMs.

10-02-2009, 07:20 AM
J King

Can you tell us what Breakout-board parts you have purchased from Machmotion so far? Some one here might better be able to answer your question.

I'm thinking you are using some thing like MachMotion's breakout board to control all your Axis-motors, coolant pumps and your AC drive.
Mach3 is just the software that runs your system. MachMotion is the hardware that interfaces your computer (PC) to the working motors of the CNC

It looks like all you need is Machmotion's normal Breakout board which has a 0-10vdc output commonly used for Spindle speed control. You then use 1 of the 10 inputs in conjunction with a rotory-encoder for your tach (speed control feed-back loop). You can use an LED and OptoSensor or photo-eye with a Rotory encoder wheel mounted on your spindle. This will give you precise speed control.

The drive also has several programable imputs. You will need to program 1 of these for your spindle direction control and then use 1 of the extra relay outputs from your breakout board to set the direction (CW/CCW)

When venturing into the unknown of control systems try NOT to look at the whole picture but rather 1 bit at a time. I know it works for me.

You need....... (from your Mach3/Machmotion)
0 - 10 vdc output
Rotory Encoder input
Relay Output

J Tiers
10-02-2009, 08:51 AM
I dont think I have ever seen a VFD that has -10-0-+10 input though.

IIRC the Invertek drives have that option. I don't know if all the various OEM versions of the Invertek also have it. They supply drives to various other suppliers under OEM agreements. For instance, the Anacon drives are Invertek, and I believe they include all the options.

I'll check on that, we do work for the US distributor.

10-02-2009, 10:04 AM
From your Omron manual

Start Command

1.) Select the mode from the Digital Operator (Key Pad) to "RE" for remote
2.) Select one of the 4 types and set in n003 - (in this case you will want #1 - for "2 or 3 wire sequence through the control circuit terminals")

This is where 1 of the outputs of the Machmotion breakout board will send a "Start Signal" to the drive

Frequency Reference (Speed Control)

1.) select the mode from the Digital Selector - n004
2.) set "Value" to #2 for 0-10vdc

This is where the MachMotion will set the "Speed Reference" for the drive

You'll also need to program the Drive's Stop/Reset Command which is n007
Set it to #1

Plenty of other "Bells and Whistels" in that Omron you may wish in incorporate or not, but you'll want to use them by enabling 1 or more of the drive's relay outputs and input them through the MachMotion's inputs.

10-02-2009, 01:38 PM
cnc4pc also has a bunch of different breakout boards, some with the analog 0-10v for a vfd. I assume the OP is using a generic parallel port?

In the manual setting parameter n001 to 10 it presets all the rest of the parameters in the system for two wire control. That is input 1 is forward and input 2 is reverse. Dont worry, the drives are protected internally so if both inputs come on it wont damage anything. In fact I think my Altivar in my mill has an extra braking mode that comes on when both are turned on.

Just make sure the dip switch is set right on the drive.

I have installed three of these step/dir to analog boards in my different machines. Put one a Digispeed GX in my mill, Installed a newer Digispeed GX in the little sherline cnc lathe at work and I had an older C6 cnc4pc board in my hercus before I changed servo drives. Arturo Duncan of cnc4pc does give great support but the boards mad by Peter Homann are steps ahead in feature, design and size. His board is about 1/4 the size of the cnc4pc one and also features a DC/DC converter option. This means you dont need to source an isolated 12 supply for the vfd side of the board. If you use the same power supply source to run the board as you use for the rest of the logic on your machine you loose the optical isolation between the drive and the computer. The DC/DC converter makes isolated 12v from the incoming 5v so it guarantees isolation. This is not as important with a VFD as the inputs are usually isolated internally but if you are working with DC drives like Minarik and KB Electronics this is needed since the analog inputs are at line potentials.

j king
10-02-2009, 08:05 PM
I have a CNC4pc board. G11 if I recall but am guessing.. Messed up my car today and have to travel Monday so all will be on hold for a bit. Will get back at it in time. I want to thank everyone here for ALL the help.

This machine would have NEVER made it this far without all the help I have received.THANKS again. Jim

10-02-2009, 11:00 PM
If it is the C11 then it has the VFD control circuit built in. Just follow the instructions in the manual for the connection to the VFD. The manual says it will need a 12v DC power supply. This can be supplied though something like a wall wart. Then just set the parameters as posted earlier.