Simple monitor hat with an LCD screen that displays current temperature as sensed by K-type thermocouple through the MAX31855 junction-compensated sensor chip. The board also buzzes at certain preset temperatures.

The Github repository has the manufacturing files and the Teensy sketch. The project is released as open hardware under the CERN v1.2 Open Hardware license.

I’ve shared the project at OSH Park so you can buy a set of three bare boards for $22.55, or $7.51 per board.

The Teensy 3.2 is available at PJRC.com or at OSH Park as an add-on at checkout. I’m using a standard 16x2 LCD screen from Adafruit.

The rest of the parts are available at Digikey. If this is your first time building a board, check out our assembly howto and remember to always buy a few extra of the capacitors and resistors. They’re very small, easy to lose, and often cost 30 cents for three but a dollar for 100.

Ref Qty Description Maker Part Number
U1 1 IC CONV THERMOCOUPLE MAX31855 SOIC8 Freescale NXP MAX31855KASA+
C1,C2 2 CAP CER 0.1UF 100V X7R 0603 Murata GRM188R72A104KA35D
J2 1 CONN TERM SCREW GREEN 2.54MM 2POS TH OnShoreTech OSTVN02A150
R1 1 TRIMMER 10K OHM TH Bourns 3362U-1-103LF
SPK1 1 BUZZER ONE NOTE 3V 4KHZ PIEZO SMT CUI Inc CMT-1603-SMT-TR