This project is an Arduino based Thermostat for universal use. I put it together rather quick&dirty since I needed a simple thermostat, and I could not find one that fit my needs... The project contains the Arduino code and the KiCad files for the board.

I ended up with a rather generic setup, that may be of use to others. The thermostat is intended to be used standalone in 12V or 24 V environments. It's settings for cooling or heating mode, for the target temperature and the hysteresis can be set without recompilation using a bridge (heating/cooling) and DIP switches (target temperature and hysteresis). A relay is fitted that can switch up to 250V and 10A. A SSD1306 compatible OLED display can be fitted as an option to display detailed information.

• Temperature measurement is done via a 10K NTC sensor
• Powered using an efficient DCDC converter (Traco TSR 1-2450E pin compatible to 7805) for operation in range of 7-36 V DC. The thermostat can easily operate in 12 or 24 V installations.
• Set for heating or cooling operation with a bridge
• Set target temperature fron 0 to 254 °C in 2°C steps via DIP switches
• Set hysteresis from 0 to 14 °C in 2°C steps via DIP switches
• 250V 10A relay. PCB design supports up to 10 A
• 2 LEDs: power indicator and switch indicator
• Optional OLED display via I2C

The PCB has been designed in Kicad. Kicad files are included in this repository, also the Gerber files that can directly be used to order the PCBs

• PCB: Gerber files are attached
• Arduino Pro Micro (with socket, if desired)
• Transistor BC547
• Electrolyte Capacitor 47 uF / 25V
• Tantal Capacitor 100 nF
• Opto Coupler LTV 817
• 2 Diodes 1N4001 or 1N4004
• 2 LEDs
• Power via DCDC Traco TSR 1-2450E, alternatively 7850
• 10x DIP Switch
• Screw Terminals 5.08 mm pitch: 2x 2, 1x 3 connections
• Relay Songle SRD-05VDC-SL-C
• Resistors: 200, 470 and 2 x 10K Ohm
• NTC 10K
• OLED Display with SSD1306 controller (optional)
• Housing