Fan and temperature controller with LCD
This module was part of the rack box project — which was terminated when I moved out of my first apartment.
FTU regulates the temperature in the Rack box. The module is equipped with a LM35 temperature sensor, installed in the top of the Rack box were it's warmest. A 80x80mm fan is also mounted at the top of the box. The air intake is at the bottom and sucks air from outside the entire closet. This gives good air circulation in the Rack box. The fan is controlled using PWM, giving the fan variable speed. It's divided into three levels: 1: 1/3, 2: 2/3, 3: full. The temperature sensor is a LM35.
When actual temperature is equal to the fan temperature the fan will start on level 1, if this persists for more then 30 seconds the fan will go to level 2. If actual temperature should rise above the fan temperature the fan is set to level 3, which is the maximum. If actual temperature is equal to the alarm temperature for more then 30 seconds the alarm will be triggered. The fan can be overridden with a manual switch, or from the external input (computer). When overridden the fan level is increased by 2 levels, meaning if 0 then 2, or if 1 or 2 then 3.
Two temperatures are stored in EEPROM, fan and alarm temperature. When stored in EEPROM the unit will remember these values even trough a power loss, the values are saved about five minutes after they are changed. In this period, when the values are changed but not stored, a "E" is displayed in the right corner if the LCD display. Fan and alarm temperature can be adjusted using the (on)-off-(on) switches, one degree at the time.
Contents
I/O
Inputs
- PB3 Fan set temp +
- PB4 Fan set temp -
- PB6 Alarm set temp +
- PB7 Alarm set temp -
- PB5 Override fan switch
- PC0 Temperature (Analog)
Calculations
- Temperature
Outputs
- PD0 LCD1
- PD1 LCD2
- PD2 LCD3
- PD3 LCD4
- PD6 LCD5
- PD7 LCD6
- PB0 Lifesignal (to Module stability monitoring unit 2)
- PB1 Fan
- PB2 Temp alarm (to Signal and lights controlling unit)
D-Sub 9-pin
- 0V
- +5V
- Lifesignal
- Fan
- Temp alarm
- LCD background light switch
- Override fan switch
Switches and LEDs
Switches
- (on)-off-(on), fan temp +/-
- (on)-off-(on), alarm temp +/-
- on-off, override fan
- on-off, background light LCD display
LEDs
- Green, Lifesignal
- Green with lens, fan active
- Red with lens, temp alarm
LCD Display
1234567890123456 25C F:30C A:30C* Fan & Temp Unit! SW v.2.0 JensenCorp.no System start =)
Source code
https://github.com/thomasjsn/AVR-Fan-and-temperature-controller
Gallery
1. test
LM35 test
Casing complete
Switches and LEDs
PCB
LCD display simulated
Assembly
LCD and LM35
Fan intake Rack box
Fan Rack box
Fan regulator
FTU installed in the Rack box
Schematic drawing
