Modbus RTU Microcontroller

Hello everyone,

I am trying to control a V20 with a microcontroller (ESP32) via Modbus RTU in C++.

I got so far, that I am able to change parameters i.e. run up time, etc. and read registers correctly.

But, I am not able to set the frequency, start the motor and change direction.

It seems that I can't simply write to register 40003 with value 4000 (frequency set value) like with other parameters.

Are there some kind of multiple register that I have to write to, in the specific order in order to start the motor?

Does anyone has experience communicating with an V20 via Microcontroller and Modbus RTU ?

Thanks

I 

I know very little about V20's, but know quite a bit about MB/RTU and Sinamics G and S drives.

In the V20, what is the value of the max frequency / rpm (p2000 in G120/S120 drives)??

If it is 4000, then in G120's / S120's, we send a scaled value to represent the speed we want.

Typical usage:  0-100% on a user interface gets scaled to 0-16384 (16#4000).

The scaled value gets sent to the Sinamics drive to speed setpoint, maybe p1070?

Then the drive scales the value internally according to max rpm. 

That's the normal path from user to motor.

If you send 4000 decimal, you are requesting ~1/4 max rpm.  Is that what the drive is doing to the motor?

Hasenburg

Hello everyone,

I am trying to control a V20 with a microcontroller (ESP32) via Modbus RTU in C++.

I got so far, that I am able to change parameters i.e. run up time, etc. and read registers correctly.

But, I am not able to set the frequency, start the motor and change direction.

It seems that I can't simply write to register 40003 with value 4000 (frequency set value) like with other parameters.

Are there some kind of multiple register that I have to write to, in the specific order in order to start the motor?

Does anyone has experience communicating with an V20 via Microcontroller and Modbus RTU ?

Thanks

Does your solution relate to USS?

I am not sure how that should work. To which register should I send it to?

Registers of V20

I can't write multiple bytes to one register. If I would do so, I would overwrite the others following registers.

Or do you mean, I should write the same command (address, functioncode, register address, value, crc) multiple times. But I am not pretty sure, that's not what you mean.

If I send 4000 to setpoint frequency (40003) is changed the register to that, but the VFD does nothing.  If I then, read 40003 the frequency is correctly set to 4000.

I did do the reset (accord. to link), but the VFD just does not react at all.

It seems like I can't control the VFD by changing any register.

What I am wondering about, are the STW, HSW, PZD Commands. There is a Register (40100:STW) that is writable and I am not sure if I should write some bit sequence to that register. I tried 0xFFFF, but and 072 Error occurred immediately.

My first understanding was to write 40004 (RUN ENABLE) to 1, then 40007 (Fault acknowledgement) to 0/1 (tried both) and then start the motor with 40006 (CMD Start) with 1. I can read out the registers and they did change, but the motor just does not react at all. The display shows 0.00 (not blinking) all the time.

By the way, Parameter P1070 (Main Setpoint Source is not a Register - can't write to that via Modbus RTU) is set to 2018.1  and I have a clue what that means and there is no sufficient explanation to that in the manual.

0_Einstein

I know very little about V20's, but know quite a bit about MB/RTU and Sinamics G and S drives.

In the V20, what is the value of the max frequency / rpm (p2000 in G120/S120 drives)??

If it is 4000, then in G120's / S120's, we send a scaled value to represent the speed we want.

Typical usage:  0-100% on a user interface gets scaled to 0-16384 (16#4000).

The scaled value gets sent to the Sinamics drive to speed setpoint, maybe p1070?

Then the drive scales the value internally according to max rpm. 

That's the normal path from user to motor.

If you send 4000 decimal, you are requesting ~1/4 max rpm.  Is that what the drive is doing to the motor?

Hasenburg

Hello everyone,

I am trying to control a V20 with a microcontroller (ESP32) via Modbus RTU in C++.

I got so far, that I am able to change parameters i.e. run up time, etc. and read registers correctly.

But, I am not able to set the frequency, start the motor and change direction.

It seems that I can't simply write to register 40003 with value 4000 (frequency set value) like with other parameters.

Are there some kind of multiple register that I have to write to, in the specific order in order to start the motor?

Does anyone has experience communicating with an V20 via Microcontroller and Modbus RTU ?

Thanks

 

The control word is often toggled between 16#04FE to 16#04FF to go from a state of "ready to run", to "run" - for G120 & S120 drives.  You will have to compare that bit pattern against the control word of the V20, and specifically of the control word as configured for Modbus/RTU.

Got it!

Main registers to write to, are 40100 and 40101.

First I have to ( I think that's what you meant) write 0x4000 to 40101 to set the frequency to 50Hz.

Afterwards I have to send 0x04FF to 40100 in order to start the Motor.

0x04FF relates to: 0000010011111111

those bits represent

• 0 reserved
• 1 MOP lower
• 2 MOP higher
• 3 reserved
• 4 Direction (0 is normal - 1 is reverse)
• 5 Communication with PLC (in my case 1)
• 6 reserved
• 7 reserved
• 8 - 15 ALL 1

In case you want to turn Motor off the bit sequence would be 

0000010011111110 = 0x04FE

The last bit turn the motor on and off.

 Thanks for your help

0_Einstein

The control word is often toggled between 16#04FE to 16#04FF to go from a state of "ready to run", to "run" - for G120 & S120 drives.  You will have to compare that bit pattern against the control word of the V20, and specifically of the control word as configured for Modbus/RTU.