Blog: Build your own Hangglider and Paraglider Winch
Remote control
With a VPN router you are able to connect to the PLC via the mobile net.
It cost around 150 euro and with openVPN you can connect up to 3 devices, typically: the PLC, a tablet as remote control and PC for remote trouble shooting/tracing and PLC update.
You can choose different models from Teltonika (RUT240, RUT901, OTD144 etc.), but the OTD144 is IP55 and has integrated antennas, which makes it a very simple component to handle.
PLC settings
Modbus on an M241 PLC is very easy to use because it requires almost no configuration. With the default setup (Unit ID 255), communication works out of the box, especially for Modbus TCP where the ID is typically ignored.
The PLC automatically exposes its internal memory (%MW0, %MW1, etc.) as Modbus holding registers. This means %MW0 corresponds to register 0, %MW1 to register 1, and so on. By linking variables to these memory addresses, they become directly accessible via Modbus.
In practice, a Modbus master simply reads or writes these registers to exchange data with the PLC.
HMI Droid
Machine Expert has a built-in HMI interface called WebVisu. It is easy to set up and has a nice design, but it does not include a lifebit functionality, and the entire design is transmitted, which makes data efficiency very low.
In contrast, HMI Droid has a built-in lifebit, and the design is stored locally in the app on the tablet/phone, so only the variables needs to be transmitted over the mobile network.
HMI Droid is a bit older and more rough in terms of how the interface must be designed, but once the design is completed, it works very well.
See the latest version of our HMI Droid screen here:
HMIdroidV1.zip?media=1722254656
Just download the app and import the files.
Data plan
With HMI Droid, you only need a data plan of around 5 GB if it runs 24/7.
However, you will probably only use it while flying, so in practice 1 GB or less is likely sufficient.