Vermes
Advanced Member level 4
The main function of this device is to measure the temperature of gas installation evaporator and the engine intake air temperature.
Main assumptions:
- displaying 3 temperatures
- monitoring the voltage of car gas installation
- adjustable LCD backlight
- Small hosting
- Easy temperature sensor connection
The main elements of the circuit:
- Atmega8
- Alphanumerical LCD display 2x16
- 3 x DS18B20 (temperature sensor)
After installation:
On the picture above there are two cables:
- One cable to the car ignition
- And the second one to parallel connect temperature DS18B20 sensors
The program is written in C.
The main function what were implemented:
- detection of number of 1 wire devices connected
- induction and activation of one of the few 1 wire systems connected to the bus
- temperature reading from a selected sensor
- measurement resolution to 0.5 degrees (view to 1 degree)
- displaying '-' for negative temperatures
- ability to enable of disable the '-' sign
- saving the display order form 1 wire sensors (saved in EEPROM)
- voltage measurement to 0,1V
- averaging rapid voltage changes (it gives a stable reference in case of small voltage fluctuations)
- function displaying “staring voltage” - the minimal voltage during engine start
- PWM LCD backlight control
Link to original thread - Termometr samochodowy z funkcją woltomierza