PIC16F876 LM60 BUZ72 ile PWM Fan Hız Kontrolü

PIC16F876 ile pwm uygulamalarında örnek olabilecek bir proje 9 adet fan kontrol edilebiliyor 3 adet BUZ72 Mosfet ile PIC çıkışları güçlendirilmiş LM60 Sıcaklık sensörlerinden gelen bilgiye göre hız değişiyor R ve G ledleri ile sıcaklık durumu gözlemlenebiliyor CC5X ile hazırlanmış kaynak C ve hex kodları devre şeması var

Firmware for the Temperaure fan controller
Version 1.2, March, 2006
Jos van Eijndhoven (jos@vaneijndhoven.net)

Intended for compilation with the (freeware)
CC5X compiler, version 3.2
see: http://www.bknd.com/cc5x/index.shtml

Note: before programming (erasing) a 16F676 device, first read
its CONFIG register and its last (0x3ff) program word!
These contain factory-programmed calibration values,
that become lost by (re-)programming!
1st sample: read last program word=343C config:’bandgap midhigh’

Operation:
TMR0 is used to count up, driven by the internal oscillator.
In ‘set_fans()’ the counter value is compared with target values
to create PWM output signals.
Four analog inputs are sampled: three LM60 temperature sensors
and one ‘minimum fan speed’ setting.
At TMR0 wrap-around all PWM outputs are activated and a limited
amount of computation is done. During the TMR0 loop, the PWM
outputs are reset one-by-one.
The PWM frequency can be adjusted with the TMR0 prescaler,
typically between 64 and 512 Hz.
A global ‘time’ is maintained for a slow reduction of fan speed,
avoiding control loop instability. Note that this notion of time
floats with the TMR0 prescaler.

The PIC16F676 performs A-to-D conversion on the 4 analog inputs, and creates a PWM output signal to drive the fans. Besides 3 temperature values, one for each group of fans, it samples a value for a shared minimum fan speed setting. On rising temperatures, the fan speed rises linearly and immediatly. On decreasing temperatures, the fan speed decreases only very slowly, to avoid control instability: from 100% to 0 speed in about 8 minutes. Lowest temp setting (turn left): 20 to 30 degrees celcius results in 0 to 100% fan speed. Highest temp setting (turn right): 65 to 80 degrees celcius results in 0 to 100% fan speed.