WattWächter TTL¶
The WattWächter TTL is a pure IR reading head designed for makers and tinkerers. The device contains only the transmit and receive electronics – an external evaluation unit is required for control and data processing. This provides maximum flexibility for custom projects.
Use Cases¶
The WattWächter TTL is designed as an expansion module in combination with:
- WattWächter WiFi/USB (cascading up to 4 devices)
- D1 Mini / ESP8266
- ESP32
- Raspberry Pi
- Arduino
- Other microcontrollers with a TTL interface
Features¶
- Reading and transmitting meter data via infrared
- TTL interface with RX / TX
- Operating voltage 3–5 V (directly compatible with 3.3 V and 5 V boards, no level shifter needed)
- Built-in reverse polarity protection
- Strong neodymium ring magnet for secure attachment to the meter
- Screw terminals – no soldering required
- Approx. 1 m connection cable pre-installed
Wiring / Pin Configuration¶
The WattWächter TTL connects to the evaluation electronics via 4 wires:
| Cable Color | Function | Board Connection |
|---|---|---|
| Brown | VCC (3–5 V) | 3.3V or 5V |
| Green | RX (data receive) | RX (e.g., GPIO3) |
| Yellow | TX (data send) | TX (e.g., GPIO1) |
| White | GND | GND |
Note
The lines are connected 1:1 (RX → RX, TX → TX), as the crossover is already done on the WattWächter's circuit board. The yellow TX line is optional for most meters (only needed for sending commands to the meter).
Baud rate
The standard baud rate for SML meters is 9600 baud.
Package Contents¶
- WattWächter TTL IR read/write head
- Approx. 1 m pre-installed connection cable
- Quick-start guide with QR codes
Additionally required:
- Evaluation electronics (D1 Mini, ESP32, Raspberry Pi, etc.)
- Custom firmware/software
- Programming knowledge
Technical Specifications¶
| Property | Specification |
|---|---|
| Dimensions (D × H) | Ø32 mm × 21 mm |
| Weight | 25 g |
| Magnetic holding force | approx. 8.5 kg |
| Housing material | PLA |
| Data transfer | TTL RX / TX |
| Power supply | DC 3.3–5 V |
| Connection | Screw terminals (4-pin) |
| Cable length | approx. 1 m (pre-installed) |
| Power consumption | < 0.5 W |
| Operating temperature | 10 °C – 50 °C |
| IR LED wavelength | 850 nm |
| Photo sensitivity | 880–1120 nm |