TechTip: Connecting a Control Techniques Drive to a Weintek HMI Using Modbus RTU

This TechTip is about connecting a Control Techniques drive to a Weintek HMI using Modbus RTU.

Demo HMI Program

For the purposes of this TechTip, we’re using a CT Comander C300 drive fitted with an AI-485 option module.

Drive Setup
Either using the drive onboard menu via the keypad, or Control Techniques Connect, software, verify the communications settings (Address, Baud Rate, Data bits, Stop Bits, Parity) as these will need to be matched in your HMI project.

Control Techniques Connect – Serial Settings
HMI Settings must match drive settings

Addressing Format
Modbus Addressing format for Control Techniques drives is:

40000 + (menu number x 100) + (parameter number)

The Weintek HMI does not require the 40000, so we can ignore that. – for example, output frequency – Menu 05, Parameter 001 would give us 501. As we may have multiple drives on our Modbus network, we’ll specify the drive serial address also for drive address 1, we’ll use 1#501 to show the output frequency of the drive with address 1, we’d use 2#501 for the same from drive address 2.
(Note, this method works for parameter numbers up to 099, which will cover many cases, however, if access to parameters >099 is required, please refer to “Using modified addressing” further down.

As usual, we have a demo project for you try for yourself, this can be run using the online simulator in EasyBuilder Pro with your PC connected to a CT Drive via a USB-RS485 cable connected to the AI-485. Download demo project here (standard addressing mode).

Using Modified Addressing to Access Parameters -> 099
To access parameter numbers >099, we’ll need to use the “modified” Modbus serial mode – these are designated with an “M”.

“Modified” settings are designated with an “M”

After changing the communication mode, reset Serial Comms using 11.020:

Reset Serial Communications after making changes.

If using modified mode, the address is calculated as follows :

40000 + (menu number x 256) + (parameter number)

Example 05.001 output frequency would be 5 x 256 = 1280 + 001 = 1281.

Demo program using the modified addressing is available here.