Make your own graphics card temperature control alarm device

If the graphics card has a temperature alarm function, it is not only convenient for daily use, but also can greatly improve the safety during the graphics card overclocking process, avoiding the graphics card being overclocked due to the inability to know the graphics card temperature in time, until the screen goes black or even "a strange smell comes out of the chassis"! I have referred to some electronic materials and tailored this over-temperature alarm for mid- and low-end graphics cards. The basic principle and production method are introduced as follows:

1. Circuit Working Principle

As shown in Figure 1, a voltage comparator is made using the operational amplifier LM358 in the circuit. The so-called voltage comparator means that when the potential of its non-inverting input (pin 3) is higher than the potential of the inverting input (pin 2), its output (pin 1) outputs a high level; when the potential of the non-inverting input is lower than the inverting input, the output immediately flips to a low level. Based on this feature, we establish an independent voltage divider circuit at its two input ends, in which the fixed resistors R1 and R2 provide a fixed reference potential for the inverting end of the op amp. The potential of the non-inverting input of the op amp is jointly determined by RT, R3 and RW. When the temperature rises, the resistance of the negative temperature coefficient thermistor RT will significantly decrease, causing the potential of the non-inverting input of the op amp to increase on the original basis. By adjusting RW, when a certain set temperature is reached, the potential of the op amp's non-inverting input terminal is just higher than that of the inverting input terminal. At this time, the output terminal is at a high level. This high level can make a low-power NPN transistor 9014 saturated and turned on, and the buzzer is powered to emit a high-frequency sound!