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The branches must be no longer than 1200 m! The main cable must be no longer than 700 m! Sometimes it is necessary to transmit over longer distances, or to run networks with spurs off the main cable run. The diagram below shows a basic RS485 cable for use with the RJ11 socket on Unitronics PLCs. Using the Solis Data Logging Stick, which uses WiFi to communicate, we were able to set up the inverter to send data to the remote soliscloud service, but we could not find any way to get capture data apart from scraping the basic status page built into the WiFi adapter which only gave watts being produced and daily output. If on the other hand each terminal can accept only a single cable, a proper branch must be created using three auxiliary terminals for each instrument to be connected. With this boards, a CBL03 lines with RJ11 connectors can branch out to support an RS485 line consisting of three discrete wires. In this case it is possible to connect the main inlet and outlet terminal directly to the terminals of an instrument without creating a branch. Two wire telephone cables will not function because in that case the ground signal levels on both sides will be floating.

RS485 is simpler because it uses only two wire (or a single pair) to carry out the data in bidirectional manner, using RS232, we need 3 wires at minimum to carry the data bidirectionally. The only way to add RS232 capabilities to the Jazz PLCs is by using the MJ20-PRG programming port add-on module. The symmetrical pin layout of the RJ11 sockets on the Unitronics PLCs allows an easy way of interconnecting the PLCs with both RS232 and RS485 communications. RS485 cable length can be as long as 1.2 km, while RS232 only about 25 meters. The wide supply voltage range also means that you can allow for a significant voltage drop along the bus (e.g., when using a bus cable of considerable length). Each device has a communication port with two terminals, which are indicated for the sake of convenience as A and B. In these two terminals the communication cable is connected so that all the devices that take part in the communication are connected in parallel. When the DSR and DTR signals are not used, the two pins can be used for simultaneous RS485 communication. Not more than one breakout board is required per RS485 line. The existence of an RS485 port on the socket makes it even a little bit more difficult.

We tried several RS485 Pi hats, but all had the same issue. RS485 is specified for multi-point communicates where multiples devices have their own address on the same communication line, while RS232 is only specified for point-to-point communications. The A signals of all devices should be connected with each other and the same goes for the B signals. It receives signals on one network and re-transmits them on another. The RS485 data transmission standard requires that each network node be linked via a single transmission line terminated at each end in its characteristic impedance. RS485 is the preferred serial communications standard for long distance industrial communications. This MJ20-PRG module clicks in the PLC and provides one RJ11 socket for serial communications with a PC. The RJ11 socket is interesting, because the manufacturer choose to have a symmetrical pin-layout, just as with the MMJ connector on DECconnect systems and the RJ45 jack in the Yost standard. PCs are normally not equipped with an RJ11 socket for serial RS232 communications.

We found panels produced by JA Solar which are 1689 x 996mm and have a 330W output, and we could fit 5 or 6 of these on the roof between the chimneys. Following being scammed by the Zero Home Bills solar panel supplier, we placed an order with another supplier whose website showed that they had the panels we required in stock, but after a few days, they contacted me to say they did not have them, and the website hadn't been updated for a long time. Our plans to upgrade our solar PV system this year are slowly progressing with installing a new Solis 1.5kW inverter and an EM112 Series Energy Meter, which have RS485 output and communicate using Modbus protocol. By using two jacks, up to 31 L485 boards can be connected in parallel for daisy chaining using readily available CBL03 data cables with no need for a hub. Using a repeater, the main cable is divided into different segments, each of which can be up to 700 m in length and connect 32 devices (this number includes the repeaters). Furthermore the total transmission line length is limited to approx.