![]() ![]() For the feed we need a black cable from Z2 to U1 pin 3 and a red cable from plus E1 to C7. In our case, however, we do not need electrical insulation, as we transmit the data via WiFi and operate the rest of the circuit with the same 3.3V supply voltage as the measuring circuit. This is fed in via the Modbus connections. Since the Modbus output circuit is operated electrically isolated from the measuring circuit via the optocoupler, an external supply voltage of 5V is required in the original circuit. This connects the resistor to 3.3V.įig: 4k7 resistor with bridge Solder the 3.3V supply voltage to the Modbus output circuit In addition, a small bridge from R19 to R17 is soldered as can be seen in the picture. It is soldered to the pads of the missing resistor R19. The 4k7 resistor serves as the Pull-up resistor for the 1Wire bus. With the resistor soldered in parallel, R15 is reduced to 320 Ohm, so that the LED of the optocoupler can be controlled from the Wemos D1 mini with a 3.3V TTL signal.įig: 1k resistor Solder the 4K7 resistor and bridge R15 is the series resistor for controlling the optocoupler U2 ( CT817C Receiving side). The 1k resistor has to be soldered parallel to R15. ![]() It is also important to note how U5 was soldered in, as the cables are soldered according to the pin numbers according to Table 1.įig: Position of U5 (unmodified board) Solder in 1k resistor This must be avoided at all costs, as we still need the pads to solder the cables. But you have to make sure that the pin is not heated for too long, otherwise the conductor track underneath will become detached from the circuit board. If you don't have this, you can heat up each pin of the IC individually with the soldering iron and carefully bend it up with a needle. The easiest way to unsolder it is with a hot air desoldering station. The IC U5 is not required because we do not use the Modbus and connect the serial TTL data signals (3.3V) directly to the Wemos D1 mini. Reduced power consumption of only 1.0mA when the Wemos D1 mini is switched off ( look here)Ĭircuit modification Unsolder IC U5 (MAX485).Own consumption: 16mA (without WiFi activity), 60mA (with WiFi data traffic, if connected).Temperature measurement: 1… 3 DS18B20 for battery, charger and inverter (operated in parallel on the 1-Wire bus).Configuration and display of the measurement data via the website.Energy display in kWh for the current day, previous day and total consumption display (not power off resistant when completely switched off, details look here).Display of the measurement data on the websiteĪfter some reengineering of the electronics I was able to modify the circuit so that it does not need an additional 5V supply and only needs a few components such as:Īnd a stand-alone boat battery monitor has been created that can:.Supports temperature 1-wire modules such as the DS18B20.Supports all PZEM modules with Modbus interface via TTL signals with unsoldered RS485 chip (U5).The Tasmota firmware already has all the important interfaces that you need to be able to build a boat battery monitor: However, it cannot be used well as a battery monitor on a boat, as you still need an external power supply of 5V for the Wemos D1 mini. In the area of home automation there are implementations with a Wemos D1 mini (ESP8266) with Tasmota firmware and a data connection via WiFi. There, however, a TTL-RS485 adapter is used to connect to the Arduino. The website is an example here Solarduino called. The Modbus protocol is open and there are some implementations with an arduino. In contrast to the PZEM-015, the PZEM-017 has no display and transmits the measurement data via the Modbus. 7 devices can be used on the Modbus via adjustable ID 1… 7, ID 0 broadcast.Modbus RTU-Interface ( RS485, 9600Bd, 8N2, binary data transmission).Energy display in kWh for the current day, previous day and total consumption display.Current measurement: 10A, 50A, 100A, 200A, 300A (from 50A via external shunt).The Peacefair company is known for various inexpensive battery monitors with LCD displays such as the PZEM-015.įig: PZEM-017 (100A version, with shunt and USB-RS485 adapter)įig: PZEM-015 (300A version as a pure display variant) While searching the Internet for a battery monitor for DC voltages, I came across the PZME-017. First of all, a few important notes that you should definitely pay attention to. ![]()
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