Temperature monitor
© Lasse Kaila 2001
FEATURES:
- Measurement of temperature using 4 sensors
- Sensors are PC standard 10k ohm NTC resistors (picture below)
- Stepless control of one or multiple 12V fan motor(s)
- Power requirement: 12V, 100mA + current for fan motors
- 8x2row LCD display, installed in 5 1/4" front bay together with 3 buttons
- Menu control, accessible with 3 buttons on front panel
- Adjustable temperature threshold values for each sensor
- Atmel AT90S4433 RISC microcontroller @ 4MHz
- Fan speed control implemented with PWM (pulse width modulation)
- Controlling MOSFET rated at 20A, max fan power 240W @ 12V
OPERATION:
- Connect power cable to standard PC power connector
- Install sensors in desired places (for example CPU, display adapter, Hard disk, computer case)
- Power up, enter settings menu
- Set desired threshold temperature (Tt) for each sensor. The setting is stored in the controller's nonvolatile EEPROM memory
- Fan rotation speed is adjusted accordingly to the sensor with the largest deviation from Tt.
- Fan is turned off if T<Tt-5C, minimum speed between Tt-5C and Tt, variable between Tt and Tt+14C and maximum at T>Tt+14C
- Temperature of each sensor is displayed on the LCD at 2 second intervals
- Blue LED on the front panel lights according to fan speed
- Red LED on the front panel is lit if a temperature is 20C over threshold
value
PICTURES:
Click here for the schematic
Block diagram of the system:
Picture of the circuit board top:
And from the bottom:
Front panel with display:
PC_temp installed and ready for use
One of the NTC sensors used for temperature measurement:
Suggestions, comments, feedback always welcome!
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Page created 12.11.2001