This temperature-controlled fan is the author of a business of high-power amplifier designed for the heat produced by the actual use, proven to work reliably. Are presented below:

The Electrical and Mechanical Road works in Figure 1. Figure IC (dual op amp LM358N) voltage detection circuit connected as windows, ICa detection limit of temperature, lCb the lower limit of detection of the temperature. R1 temperature and composition of components 3AX31C temperature / voltage conversion circuit, when the temperature of the PN junction due to the rising 3AX31C resistance decreases, the circuit point A potential rise; the other hand, when the temperature is lowered, A point of potential decline. A potential point of ICa and ICb determine the level of output high or low, the output level changes are used to promote the implementation of the circuit after the signal level. The following describes the working process of the machine. Power at the beginning, because the radiator is still at room temperature, the temperature sensing element is pressed on the radiator, so the greater the resistance presented, A point potential that the op amp feet are low-potential in set foot potential, ICa, ICb are low output, T1, T3 end, T4 bias and conduction from the R7, C point of low potential, T5, T6 composite pipe end. In addition, B point for high potential through the relay coil, so that T2 has ended, the circuit is in standby state. When the temperature reached when the lower limit set, ICb feet by potential higher than the output pin high, the conduction T3, T4 cut-off, but because of the role of R9, T4 remains low point after the closing of potential C , the circuit is still in standby mode. When the temperature continues to rise to the set when the upper limit, ICa feet feet higher than potential output high to turn T1, C point to immediately jump into a high potential, T5, T6 conduction, J actions, the normally open contacts closed, the fan may start rotating electric cooling, T5, T6 turn down potential after the B point to T2 turns on, the point potential locked in the high C on. When the temperature is lower than the upper limit, ICa output flip cut-off low to T1, but T2 self-locking effect in that the C point is still to maintain a high potential, so the fan will not stop. When the temperature is lowered when the lower limit, ICb turn out low, T3 end, T4 turns on, the potential low point C, so the T5, T6 end, J release, the fan stopped. Since then the temperature rises, the circuit and repeat the process. This circuit can set the fan in the upper and lower operating temperature range of cooling, temperature control circuit which overcomes the narrow scope of the past, fans start the frequent shortcomings. Production and commissioning of the circuit requires a genuine device, particularly strict requirements on the IC. Used here to compare IC, requiring low output must be "0" V, or can not use. I have replaced in the assembly process had MCl458, NE5532P, TL082, LM833 op amp, etc., were in the low 1 ~ 2V output voltage, resulting in power just when connected, J will pull, so to choose to use IC . Figure 2 is a printed map. When the temperature sensing element should be installed close to the power amplifier tube radiator installed to minimize the thermal resistance, such as a radiator charged should be noted that insulation. If the temperature sensing element connected dual-core shielded cable should be used too long. Installation, commissioning is simple: first Wl W2 spin to the ground side of the power amplifier connected to the radiator to heat up. His hand touched the radiator, feeling hot after the transfer W1, so that J pull start fan to cool. Radiator to be cooled to feeling slightly hot tune W2, the J release, so repeated several times, until your satisfaction.