Max. Temp. Detector for Fan Controller

The fan controller circuit for the Titan 2000 and other AF heavy-duty power amplifiers, published in the May 1999 issue, has an output that sets a voltage if the fan controller reaches the end of its range. Since the controller responds to temperature, this signal is seen by the amplifier protection circuitry as an overtemperature indication. The disadvantage of this output is that the maximum voltage for the fans is not constant, but depends on the load (number of fans, defective fans) and the mains voltage.

Resistors:
R1 = 22kΩ
R2 = 120kΩ
R3 = 10kΩ
R4,R6 = 1kΩ
R5 = 1MΩ
R7,R8 = 47kΩ
R9 = 3kΩ9
R10 = 100Ω
P1 = 5kΩ preset
Capacitors:
C1,C3 = 100nF
C2 = 100µF 25V radial
C4 = 47µF 25V radial
Semiconductors:
D1 = LM385-1.2
D2 = BAT85
D3 = high-efficiency-LED
D4 = zener diode 16V/1W3
T1 = BF245A
T2 = BC547B
IC1 = TLC271CP
Miscellaneous:
K1 = 2-way PCB terminal block, raster 5mm
K2 = 3- way PCB terminal block, raster 5mm