Simple optical probe to reading electricity meter, compatible with IEC1107 (IEC 62056-21).

The optical probe is suitable for reading electricity meters Actaris, Elster, EMH, Landis Gyr, Iskra and many others compatible with IEC1107 (IEC 62056-21). Very simple construction, only 9 cheap, generally available elements. Reading after connecting with a USB cable to a computer/laptop/phone using a terminal (HTerm, Terminal, etc.) or a dedicated program. Works at speeds:

• 300 baud
• 600 baud
• 1200 baud
• 2400 baud
• 4800 baud
• 9600 baud
• 19200 baud

The operating speed depends on the optical elements used - the transmitting diode and the phototransistor.

USB to Serial chip CH330 is used for communication. If you don't have a CH330, don't worry - you can use a simple USB-UART adapter instead. However, you should short-circuit J1 and J2 on the PCB. The connection diagram is below:

BOM:

C1,C2 - 100nF SMD0805

R1 - 220ohm SMD0805

R2 - 1kohm SMD0805

U1 - CH330 SOP-8 SMD (or adapter USB-UART)

U2,U3 - 74LVC1G04 SMD

IR1 - L-34F3BT or similar THT 3mm

IR2 - BPW85C or similar THT 3mm

Ring magnet 30/15mm

Case (3D print)

USAGE

You can use a ready-made program to read the contents of the OBIS codes of an electricity meter or use a regular terminal program. To communicate with the meter, you must set the appropriate parameters in the terminal:

300 baud rate

parity (Even)

7 data bits

1 stop bit

We send the string "/?!\r\n". The energy meter then has a maximum of 2 seconds to respond, and the response is first a meter identifier frame, which has the form "/XXXZD", where XXX is the manufacturer's identifier, D denotes the meter identifier (maximum 16 characters) and Z denotes the speed identifier at which the meter can communicate, to increase the transmission speed from 300 bd to higher. When it comes to changing the data transmission from the meter, this should be done only after receiving the identifier frame, but if you do not do this, the meter will provide data at a speed of 300 bd. If you want to change the transmission, you should send the meter a frame "VZY\r\n" (after receiving the identifier), where V is the digit 0, the Z field plays the same role as the character in the identifier frame, and Y identifies the type of operation performed in and "0" means reading data, and "1" programming. From the counter we can get digits that mean:

0: 300 bd

1: 600 bd

2: 1200 bd

3: 2400 bd

4: 4800 bd

5: 9600 bd

USE IN PRACTICE

We will use the free program HTerm (available for download from: https://www.der-hammer.info/pages/terminal.html). After starting the program, select the appropriate COM port and set the transmission parameters according to what was written above (marked in red in the photo below):

First, we send a string of characters: "2f3f21"(hex) which is equivalent to "/?!" for ASCII codes. The counter will respond by sending a counter identifier frame. Now, important! - within 2s, we send another command "06303030"(hex) - which corresponds to the command "000" in ASCII. After a while, the counter will start transmitting available data with a transmission of 300 baud.

Link to video of construction and operation: https://youtu.be/O1nidmIo3FE