All about W1209 Temperature Controller

What is the W1209 Temperature Controller?

According to variations in temperature, the surrounding environment may need to be adjusted in particular instances. So, controlling temperature as per the requirements in the incubators, refrigerator, healthcare, food and beverages, etc, In that case, the W1209 temperature controller comes to mind, this is an embedded device that can control the output of coolers and heaters according to temperature changes. 

W1209 temperature controller

Using the high accuracy temperature sensor, the W1209 Digital Temperature Controller allows you to intelligently control power to the electrical devices. You don't need to know how to program the controller. Configuring the settings, on & off trigger temperatures is possible using 3 switches. The relay has a maximum switching capacity of 240V AC at 5A or 14V DC at 10A. The current temperature is shown in degrees Celsius on the three-digit segment, and an LED shows the relay's current condition.


Example: Here is the best example of when you would need this device,  Are you all familiar with how to turn on or off a regular fan, which is frequently used in residences? The solution is manual, am I correct? However, if you use this W1209 controller, you can set it to automatically turn ON or OFF when the temperature reaches a certain preset value.

Features and Specifications:

Temperature Range

-50 to 110-degree Celcius


0.1 degree C

Input Voltage

12 V DC

Refresh Rate

0.5 sec

Input type

NTC(10K 0.5%)

Relay output range

240 V AC or 12 V DC

Relay I capacity


Pin Configuration:

Pin Name


Sensor i/p connector

NTC sensor

Sensor o/p connector

NTC sensor


Relay contact 1


Relay contact 2

12 V

i/p Voltage



W1209 Circuit

W1209 Circuit

The main component of this temperature controller is the eight-bit STM8S003F3P6 microcontroller, it is the brain of the system. The onboard 8 kB flash memory of this controller is more than sufficient for the thermostat requirements. The NTC probe is part of a resistor divider with R2 and is driven by a stabilized voltage of +5 V. The sensor voltage is sent through pin 3.  The transistor T1 and its relay are connected to the output PA3 through the resistor divider R7/R1.  The output of the +5V is given to the LED from the processor.

How does W1209 work?

How does W1209 work

The W1209 has three seven-segment displays to show the temperature readings, as well as sensor probes that connect to waterproof NTC temperature sensors. Relay is retained in place and has two outputs that link to external devices. The board has two inputs: 12V DC and GND. There are buttons labelled SET, INCREASE, and DECREASE. The operation is controlled by a single controller.

The thermostat sensor module includes several switches mentioned before, "SET," "+," and "-," which can be used to display and set various thermostat sensor module characteristics. Let's examine the customization and setting of the parameter values. There are Seven parameters two set up and work with this controller. P0, P2, P3, P4, P5, P6.

Trigger Temperature: 

Press the "SET" button to adjust the trigger temperature. It will flash on the seven-segment display. The "+" and "-" buttons now allow you to set a trigger temperature (in Celcius) in steps of 0.1 degrees. The trigger temperature will be stored and the display will restore to the current temperature if no buttons are pressed for about 2 seconds. If NTC waterproof sensor is not connected to the rob it displays the “L L L” which means the sensor is not connected to the controller. After pressing the SET button, it displays the P0, you can change it by pressing the +/- button.

P0 (Heat or Cool): 

Cool (C) - The default setting in the controller, the relay will get energized when the temperature reaches the threshold.  

Heat (H) - If you set it to the heat, which means the relay will get de-energized when it reaches the threshold.

P1 (Backlash or Hysteresis parameter):

This operation prevents the continuous triggering means it defaults set to 2, If you SET the temperature value at 30 degrees, It will trigger the relay at around 28 degrees Celcius, not 30 degrees Celcius.


P2 (Upper limit):

This limits the maximum trigger temperature you can set. In addition, it acts as a safety measure to prevent users from setting an extremely high temperature.

P3 (Lower Limit):

This limits the minimum trigger temperature you can set. In addition, it acts as a safety measure to prevent users from setting an extremely low temperature.

P4 (OFFSET correction)

It changes the value, the difference between the actual temperature and displaying temperature.

P5 (Delay Parameter):

This parameter is set at a time when the relay trigger after the temperature reaches.

P6 (Alarm Parameter):

The display will show the “ - - - “ condition when the temperature reaches its setting.

How do I reset my W1209 temperature controller?

Hold both + and – a while to reset to factory settings. After 5 seconds the Controller will return to the thermostat function.


  1. To control fan/heater/cooler wirelessly
  2. Preset or setpoint temperatures
  3. Central Heaters/Coolers
  4. Water Heaters
  5. Refrigerators

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