Air temperature regulation in a chamber for rotary forcespinning

Air temperature is an important factor related to evaporation process of the solvent during the production of nanofibers using rotary forcespinning (RFS). An air temperature regulation system was developed to maintain the air temperature of the RFS chamber with a volume of 63 dm
³
. It consisted of an AC (alternating current) heater (220V, 50Hz, 350W), a temperature and humidity sensor SHT11 (DT-SENSE), a dimmer circuit managed by an ATmega 8A microcontroller, a PWM (pulse width modulator) managed by an ATmega 16A, a DAC (digital to analog converter) circuit built in a low pass filter (LPF), and displays (LCD and computer). A proportional-integral-derivative (PID) control action was applied to maintain the air temperature in accordance with the desired temperature. The Kp, Ki, and Kd constants used by the PID controller were determined by employing the second Ziegler-Nichols tuning method. They were Kp of 18, Ki of 32.5, and Kd of 8.125. For the desired temperature ranging from 34 to 40
^o
C its settling time was in the range of 451 to 950 s. The response was therefore quite fast response. The rise time was about 200 s for the desired temperature in the range of 34 to 38
^o
C and 400 s for that of 40
^o
C. The overshoot was 2
^o
C at maximum and the steady-state error was 0.1
^o
C. Considering the obtained controller parameters, the air temperature regulation in the chamber for RFS could be regarded as a good control system.