VFD to Servo Converter Card

This is an interface card which on one hand connects to the PLC or CNC controller and receives input like Pulse - Direction signal (5 - 24)V / 4 to 20ma current signal / 0 - (5-24) volt analogue signal (adjustable) / input from another SSI encoder and controls standard Induction motor through any standard VFD. Parameters can be programmed like scale, acceleration, response, backlash etc. This is basically an alternative to 'not so critical' servo applications at less than half the cost.

There are numerous application where movement is required to be controlled in 1 deg of precision, like machine tools (10 to 15 micron resolution with 5mm ball screw), two sides of a long crane, or automatic indexing, precise controlled conveyors, printing machinery etc. These applications do not justify the cost and complexity of Servo drives.

Technically VFD to Servo Converter Card   EE V2S 01A takes the load of calculations relating to load, breaking, overrun, backlash etc and accordingly sends voltage signal to VFD. It also sends signal back to the controlling device about its positional status. Besides that it can electronically control limits also. The user can fix the start and end points or connect standard limit switches to input lines, and it will not allow the motor to go beyond it. It also keeps the record of its travel and can automatically go to pre-set fixed location just with the press of a single button.

Specifications and Limits.:-




Power Supply

12 to 24 volts DC, 0.5 A

Ensure clean supply.

Inputs X0-X4, Pulse, Dir.

DC 5 to 24 volts. 200 KHz.

Pull Down 1k5

Output Y0 to Y3

Open Collector, 30ma, 40v,1 KHz

Freewheeling Diode to Vcc

Output Y4 to Y5

As above, 10 KHz

Connect to M0, M1 in VFD

Output Y6 to Y7

Analogue Out to VFD

Connect to AVI in VFD

ANALOG 1 & 2

0 to 5 / 24 volts. Peak adjustable.

For Analogue motor control.

Encoder Aux & Main

5 volts Magnetic, absolute, SSI

2048 PPR (8192 Div.)

Serial Interface

5 Volts, support Txd, Rxd protocol

Baud 9600, 8 Bits, No stop.

Two Digit Display

Displays the Parameter number & value. Also display position.

Selected by P. Buttons at the bottom (Select, Inc., Dec.)

Two LEDs (Para / value)

Tells, what display is Showing.

Both glow is Error





(1).    Can take the input signal of different type, individually or jointly. So you can simultaneously control the motor from a PLC as well as run it in relation to another motor in electronic gearing mode. This is a unique feature where you can run slide ‘A’ in relation to slide ‘B’ as well as add or subtract additional controlled movement. It can give you complex input structures also. Like you can connect a potentiometer to determine as how much you wish to travel per pulse input.

(2).    It takes care of the mechanical stresses and controls the motor accordingly. Like a motor is running a load up or down against gravity. Here you don’t have to worry about the different settings of power. It will run the motor in contestant speed irrespective of the varying load conditions.

(3).    All settings re-programmable more than 1,00,000 times.

(4).    Rugged in construction. Most of the servo motors caution you against mishandling, hammering etc. because of delicate encoder and brittle magnets inside. This device is supplied with the most rugged magnetic encoder, where you don’t have to worry about mishandling. The induction motors are in any case rugged in construction.  

(5).    It can electronically control limits. So now you can feed in that motor should not go beyond 1212 mm and should not cross the start zero point. You do not need any additional limit switch for it. You can enter up to four limits, where the motor stops at one of them and waits for another command to go beyond this limit.

(6).    It can communicate with other devices through “serial interface” (5v). It follows standard RXD, TXD and ground pins, baud rate 9600, 8 bits data, no stop or parity bits.

(7).    Analogue signals are adjustable for 0 to maximum limit. If you need your analogue signal to vary from 0 to 5v or 0 – 15 volts, you can adjust the “calibrate analogue 1” and 2 pre-sets to set the upper limit. Factory set is 0 – 10 volts.

(8).    Data inputs are simple. Three miniature push button controls on the device can enter or alter any setting. You don’t need any computer or special device to program your parameters.

(9).    It is capable of handling two motors simultaneously but at some extra cost. All the features required for second motor control are in-built.

(10). Technically superb this is not just an Interface Card, rather a complete system in itself. Yet “Most Economical”.

Connector Pin Detail. :- Two 10 pin connectors on the left, pin count starting from top.

marked “Com” on first pin and “+24v” on last Pin.







This the circuit “Ground”. Connect the 0 volt of DC supply, ground pin of PLC & VFD, common pin for Open collector outputs. Pins 1, 2 are Shorted.





These are general purpose Configurable digital outputs as feed back to PLC. It can represent limit crossed, system On, position achieved, motor locked etc. If no such control is required,  user can ignore them. Pins open collector outputs with pull diode to Vcc. Can sink 30ma max at 40v DC.









Forward Direction Control for Motor “1”. Connect to “M0” in VFD



Reverse Direction Control for Motor “1”. Connect to “M1” in VFD



This is 0 to 10 volt input to VFD for motor “1”. Connect to “AVI” in VFD



This is 0 to 10 volt input (AVI) to VFD for motor “2”.



This is analogue supply line (10v) input from VFD.



This pin will receive the “Direction signal” from PLC. 0v means “Forward”.



This pin will receive the “Pulse” from PLC. (Pulses per revolution to be set)



These are general purpose Configurable digital inputs from PLC or switches. These can be limit switches, limit cross command, system On, emergency stop, clear all etc. If no such control is required,  user can ignore them. Pins accept 5 to 24 volts in as High input irrespective of supply voltage.











This the circuit “Supply”. Connect here DC input supply  +12 / +24 volt, 500ma max. Pins 19, 20 are Shorted inside.


24 V

Front Panel Controls :-  A three pin screw terminal, Two pre-sets, three push buttons all located at the bottom side, and two ‘D’ type 9 Pin female connectors, one ‘D’ type 9 Pin male connector located at the right side control many different functions. Details given below.








I st left connector at bottom

Common Point for “Analogue Inputs”.



II nd left connector at bottom

Analogue Input for Motor “1”.



III rd left connector at bottom

Analogue Input for Motor “2”.



I st Pre-set bottom left position

Calibrate Analogue Input 1. Adj. 5 – 24 v



II nd Pre-set bottom right position

Calibrate Analogue Input 2. Adj. 5 – 24 v



Left Push button at bottom.

Selects parameter number & its value.



Middle Push button at bottom.

Increases parameter number & its value.



Right Push button at bottom.

Decreases parameter number & its value.



Bottom, right side 9 Pin D Female

Connects to encoder-2 for add on control



Middle, right side 9 Pin D Female

Connects to Motor encoder.



Top, right side 9 Pin D male

Send & receive Data to external device.


Let us Start. :-

Lots of Variable Frequency Drives are available with many varying features. Since this device takes care of all the relevant parameters, so we are left with only one thing to consider. Chose a drive with maximum “Torque” and maximum overloading capacity. No special features like Mod Bus interface, 4 – 20 ma input etc. Even display is not needed.

 We don’t need to be choosey for motor selection. Any good motor as far as it fits in your system will work fine.

(1). Change Control mode as AVI with M0 as Forward run and M1 as Reverse run.

(2). Set acceleration and retardation to 0.1 second.

(3). Mechanically couple and connect the “Rotary Encoder” supplied with this device.

(4). Connect the “Power supply 12 / 24 volts & Input signals of Pulse and Direction to Y7 & Y6 from controlling device (PLC). The only precaution is that PLC should be in “Common Ground Mode”.

If you wish, we can also supply complete set of Motor, VFD and V2S device with encoder duly coupled and ready to run. The choice of the manufacturer will be yours.


Dimensions :-

We recommend minimum 40mm space to be left on left, right and bottom. Top spacing can be 20mm. Total space required will be approximately 180 mm wide X 200 mm high. Device should not be placed above VFD or heat producing devices. connecting cables should be 0.25 mm sqr.

Programming Procedure :-

Programming procedure has been kept very simple and user friendly. Following steps will enable you to program the EE V2S 01 A card.

(1). Connect the 12 / 24 volts DC supply to the card supply pins and turn ‘On’.

(2). Press and hold the “SELECT” button for a few seconds till display shows 00. This is the location of Parameter Number 00. A LED (Parameter) on the right side of the Digits will glow to show that this is Parameter number.

(3). You can chose the Parameter number of your choice by the “INC.” or “DEC.” push buttons. When you reach the desired number, press the “SELECT” button again and the display will show the value of the Parameter. The right side LED will shift to “Value”.

(4). Now you can alter the value by the “INC.” or “DEC.” push buttons. When you reach the desired value, press the “SELECT” button again and the display will blink and will shift back to show the Parameter number. The right side LED will shift back to “PARAMETER”.

(5). Repeat the Step – 3 and Step – 4 to input all the values.

(6). When you are done with all the values, press and hold the “SELECT” button again till it accept the values. The display will go blank. Leave the button and re-cycle the power. You are ready with the new parameters and ready to start the drive.

Applications :-

The industry is constantly moving towards automation. This device is the stepping stone, which combines flexibility and simplicity both. It provides input for all types of user. Typical uses to name a few are :-

(1). Long cranes, flat conveyors (chain on both ends),   need parallel movement on both tracks. This device ensures total parallelism by controlling one side motor with reference to the other side motor.

(2). Machine tools like surface grinders, roller grinders need consistent increment per rotation or per travel length. Just a small limit switch on one end with this device does the job.

(3). Extruding conveyors need pull in accordance to the extruder or ram movement. Again one proximity switch with this device does the magic.

(4). Many application need cutting or marking or measuring, like cloth, cables etc. You can feed in the length required and each push of a button will move and stop it at the place.

(5). Semi precision machines like pre machining CNC parts need to be controlled in 100 microns or above. Simple PLC with this device will convert the normal machine to a CNC in less than half the cost.

The uses are numerous limited only by the imagination of the user. This is a border between manual machines and full CNCs. This device gives you a choice to adopt to “LOW COST AUTOMATIO”. For any type of advice or suggestion feel free to call us.

Cost Considerations :-

Let us take the case of Delta. Let us consider 5 HP / 3.75 Kw. We are taking actual available price of similar product line of the same company.

Approximate cost of Motor + VFD + EE V2S 01A + Encoder = 38,000/=

Approximate cost of Servo Motor + Drive = 80,000/=

Our complete system costs only 48 % of the servo system of the same size. A net saving of more than 50 %.

Knowledge Base :-

What is Pulse – Direction signal or command. :- Unlike general motors, servos run very precisely, normally to 10,000th of a rotation. These motors are normally programmed to run on these pulses in accordance to its lead screw pitch. If we set it to run the 5mm pitch lead screw, 5000 pulses per revolution, that means each pulse will move it by 1 micron. So we give as many pulses, as many microns we need to move. These pulses are generated by either a PLC or a CNC system. The direction signal tells it, which direction to move.

What is 10 volt / 4 to 20ma signal :- Many application demand consistent movement rather than calculated movement. A simple pot varying from 0 to 10 volts will give complete control of the motor. A 4 to 20 ma signal is more consistent in industrial environment. 4ma is considered as zero and 20 ma as maximum. A current signal can travel long distances and is less susceptible to disturbances.

Standard Accessories


As standard supply, EE V2S 01A comes with one Absolute Rotary Encoder 2048 PPR. But few additional accessories can enhance its capabilities.

(1). Additional Rotary encoder 2048 PPR absolute SSI interface connects directly to the device for electronic gearing and proportional travel.

 (2). Magnetic teeth sensor. There are places where fitment of a encoder is typically not desired or where existing machine with some gear is required to be the speed / travel sensor. The gear teeth sensor fits in such application directly and it is much cheaper also.  

(3). Signal Converter. This device converts different types of signal in to simple voltage /  current / pulse signals. Like signal from load cell, mod bus signal,

(3). If you still need more, tell us. We can develop special devices to suit your type of requirement.


Other similar Products. :-

(1). Universal Programmable Rotary Encoder. This is an All-in-one encoder which can be set to give any type of output for any PPR setting. It is a software based encoder and Contains No graduated metal or glass disk or delicate parts. It can withstand Over Speed Jerks and jitters without losing a pulse. It can become incremental, absolute, multi-turn, speed-meter, counter, DRO, resolver and direct motor controller.

(2). Hydro – servo valve :- It can control hydraulic cylinder just like a servo motor – controller set. It replaces Ball screw + Servo motor + controller and puts in a most rugged hydraulic system.

(3). Low Cost DRO. :- It is standard Digital Read Out which costs only 25 % of the normal industrial DROs. Least Count is 10 microns.


(1). The device is designed with protections against voltage spikes and field disturbances. However user must ensure clean power supply.

(2). The product is in constant development. Many features are modified for better performance. Kindly ensure the correct data sheet matching the product extension. This datasheet refers to extension “A” (EE V2S 01A).

Frequently Asked Questions. :-

(1). If this device can cut so much cost, why not everyone uses it.

Ans. :- There are two major factors where a Servo System has an edge. (a). Response time – Since it is an indirect control and VFD has its own delays, so it takes almost 0.1 seconds to respond which should be considered in high speed application. (b) Locking – When reached the set point VFD turns off, whereas servos keep energized to maintain the position. This device may hunt for position if load has a self return tendency.

(2). What is backlash control.

Ans. :- Since this device is designed to fit even in simple mechanical machines, where a lead screw instead of a ball screw is used. Lead screws have a back lash. This device will add the backlash to enable the tool follow the correct path, whenever the command reverses direction.

(2). Why there is a parameter called “Play”.

Ans. :- “Play” specify positional accuracy. As mentioned above this device hunts for the position. If we set the “play” too low (high positional accuracy), it will achieve better position but will take longer time to settle. So it is recommended to keep the positional accuracy only as much, as is expected from the tolerance of the job.

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