Getting Started¶
The WattWächter TTL is a pure IR reading head and requires an external evaluation unit to operate (e.g. ESP32, D1 Mini, Raspberry Pi or Arduino). This page walks you through the initial setup step by step.
For the setup you need:
- An evaluation unit (D1 Mini / ESP8266, ESP32, Raspberry Pi, Arduino, etc.)
- Your own firmware/software to read out the data
- A prepared digital electricity meter (SmartMeter or eHz) with the PIN from your grid operator
Prepare the meter first
Before connecting the WattWächter, your electricity meter must be unlocked (PIN from your grid operator). Follow the Meter Preparation guide to do so.
1. Wiring¶
The WattWächter TTL is connected to the evaluation unit via 4 wires:
| Wire color | Function | Board connection |
|---|---|---|
| Brown | VCC (3–5 V) | 3.3V or 5V |
| Green | RX (data receive) | RX (e.g. GPIO3) |
| Yellow | TX (data transmit) | TX (e.g. GPIO1) |
| White | GND | GND |
1:1 wiring
The wires are connected 1:1 (RX → RX, TX → TX), as the crossover already takes place on the WattWächter's circuit board. The yellow TX wire is optional for most meters (only required to send commands to the meter).
Power supply
The WattWächter TTL operates at 3–5 V and is directly compatible with 3.3 V and 5 V boards. No level shifter is required. A built-in reverse polarity protection guards the device against incorrect wiring.
2. Position the reading head on the meter¶
The WattWächter TTL attaches magnetically to the meter via its neodymium ring magnet. Position it directly over the IR interface (infrared diodes) of your SmartMeter.
PIN activation required
For your meter to transmit measurement data via infrared, the extended data display must be enabled on the meter. To do this you need the PIN code from your grid operator. Enter it directly on the meter, then set PIN to Off and Inf to On in the meter menu.
3. Read out the data¶
Data transmission is serial with a standard baud rate of 9600 baud (SML). Configure the serial interface of your evaluation unit accordingly and parse the received SML telegrams.
Concrete examples with wiring diagrams and source code can be found under:
OBIS codes
An overview of the OBIS codes that modern meters provide (tariffs, voltage, current, power, phase angle, device info) can be found under Additional OBIS codes.