W1209 Digital Temperature Controller — 12V, -50°C to 110°C Thermostat
The W1209 is a self-contained digital thermostat with a relay output, a 3-digit LED temperature display, and a waterproof NTC thermistor probe — all on a board small enough to fit inside a project box. Set the target temperature and hysteresis via three push buttons; the relay energises when the temperature drops below the setpoint (heating mode) or rises above it (cooling mode). At 12V, the relay switches up to 10A at 240V AC or 10A at 30V DC.
- -50°C to +110°C range — NTC thermistor probe included
- 3-digit LED display — 0.1°C resolution
- Relay output — 10A at 240V AC or 30V DC
- 12V supply
- Heating or cooling mode — configurable
- 0.1°C hysteresis adjustment — prevents relay chatter
| Specification | Value |
|---|---|
| Temperature range | -50°C to +110°C |
| Display resolution | 0.1°C |
| Relay rating | 10A / 240V AC or 10A / 30V DC |
| Supply voltage | 12V DC |
| Modes | Heating (H) or Cooling (C) |
| Probe | NTC 10K waterproof |
How do you set the W1209 to cooling mode?
Hold the SET button for 5 seconds to enter parameter mode. Navigate to the P0 parameter and change it from H (heating) to C (cooling). In cooling mode, the relay activates when temperature rises above the setpoint; in heating mode, it activates when temperature falls below. The hysteresis (P1 parameter) sets the dead band to prevent relay oscillation around the setpoint.
Best for
Homebrew fridge temperature control, incubator temperature regulation, 3D printer heated bed thermostats, aquarium heater controllers, greenhouse frost protection, fermentation temperature control, and any 12V-powered project needing automatic relay-switched temperature control.
Why Kunkune
Shipped from UK stock. 60-day returns, no minimum order. Fast Royal Mail delivery.
For logging temperature data rather than switching a relay, the DS18B20 waterproof probe reads over One-Wire to any Arduino.
Buying in bulk? For orders of 10+ units, contact us for trade pricing.
