NIXIE THERMOMETER

 

Introduction

I was browsing through the February 2011 edition of Elektor magazine when I saw this project using Nixie tubes. The circuit is a mixture of the old and new.

Nikie tubes were around before the invention of much cheaper and more reliable LED's and seven segment displays. A nixie tube is usually used to display numerals. The glass tube contains a wire-mesh anode (+) and multiple cathodes(-), which are shaped like numerals. Applying power to one cathode makes it glow with an orange coloured discharge. The tube is filled with a gas at low pressure, usually neon.

Nixie tubes were first produced in the 1950's and continued in production in Russia until the 1990's. This project uses a DS1820 one-wire temperature sensor connected to an AT89C2051 micro controller. The micro controller processes the information from the sensor and drives the nixie tubes.

Features

Display range: 00 to 99 (Celsius or Fahrenheit)

Temperature sensor: Maxim-Dallas DS1820, accuracy 0.5 K

Power supply: AC power adaptor, 12 V to 15 V DC

Current consumption: 170 mA at 12 V

Tubes: Russian IN-16, 13-way solder connections

Microcontroller: Atmel AT89C2051 (this came ready-programmed)

Firmware: BASCOM (source and hex files available for free download)

Options:

- choice of Celsius or Fahrenheit display

- tube illumination

- LED trend (warmer/colder) indicators

 

Download full design document (pdf)

Checking the calibration of the thermometer