Thermo Plug

The thermo plug is a small board for measuring temperature and controlling an output device.

One of three different types of temperature sensor can be used:

  • a 100 kΩ NTC/thermistor (glass types can go up to 300°C)
  • a K-type thermocouple (up to 1000°C) with a matching AD597 thermocouple chip
  • a 1-wire DS18B20 sensor (up to 125°C)

The DIO pin is tied to a transistor and can be used in different ways:

  • to generate a sound, using an on-board piezo buzzer
  • to drive a relay, with an on-board protection diode
  • with an opto-isolated triac (off-board, also requires a limiting resistor)
  • with a small / low-current DC motor, again with on-board protection diode

The positive output is connected to PWR, not 3.3V, to allow for higher-power use (and a louder buzzer).


There are no switches or jumpers to configure, but you must choose which components to add.

Select one of these three input options: an NTC, a 1-wire temp sensor or a thermocouple.

> With the NTC, add R1 - use a 1kΩ resistor with a 100 kΩ NTC for high temperatures.
> With the 1-wire DS18B20 temperature sensor, add R3 - a 4.7kΩ resistor.
> With the termocouple add the AD597 IC and C1, a 0.1µF decoupling capacitor.

The standard kit provides all the parts for this last option: the AD597, the 0.1uF capacitor (both already mounted on the PCB) and the thermocouple.

Select one of these two output options: a piezo buzzer or an external relay.

> When used with a relay or other inductive load, add the D1 protection diode.
> In both cases, add R2 - a 1 kΩ resistor - as well as Q1 (any small NPN transistor will do).

The standard kit provides the parts for this last option: the 1 kΩ resistor, a suitable NPN transistor and a buzzer (observe polarity!) to solder on the board.

Header Pinouts

Design Info

Dimensions: 21.1 x 31.8 mm
CadSoft EAGLE design files: see below.
This plug can be operated at 5V as well as 3.3V (the AD597 is connected to PWR, not +3V).

This board uses the conventions of a JeePlug and can be used with the ports on a JeeNode. It can also be used with other boards and MCU’s, if you hook it up properly and adapt the interface code for it.

How to Get It

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