Simple artificial intelligence temperature control circuit

Introducing a temperature control circuit with simple artificial intelligence. When using this circuit for temperature control, you only need to turn the switch to the 2 position, control the temperature by setting it, and display the temperature value displayed by the 3-and-a-half-digit meter. The temperature can be accurately controlled, making temperature control operation very convenient. 1. Circuit working principle The LM35 voltage integrated temperature sensor is used in the circuit, making the circuit very simple. Related pictures of this topic are as follows: LM35 is an integrated temperature sensor with calibrated internal circuit. Its output voltage is proportional to the temperature in degrees Celsius, with good linearity, high sensitivity and moderate accuracy. Its output sensitivity is 10.0MV/℃, and its accuracy reaches 0.5℃. Its measuring range is -55-150℃. The self-heating effect is low at rest temperature (0.08°C). The working voltage is wide and can work normally within the power supply voltage range of 4-20V, and consumes very little power. The working current is generally less than 60uA. The output impedance is low, 0.1Ω at 1MA load. According to the output characteristics of LM35, when the temperature changes between 0-150℃, the corresponding voltage at the output terminal is 0-150V. This voltage is divided by the potentiometer W3 and then sent to the 3.5-digit digital display meter. (composed of ICL7107 and related circuits) detection signal input terminal. When the input voltage at the input terminal is 150V, adjust the potentiometer so that the displayed value is 150.0. After adjustment, the value displayed on the digital display head is the actual measured temperature value. Temperature control selection can be achieved through potentiometer W2. By adjusting W2, the voltage of the intermediate head can be changed within the range of 0-1.65V, and the corresponding control temperature range is 0-165°C, which can fully meet the general heating needs. Set the switch K to the 2 position, and the voltage at the middle head of the potentiometer W2 passes through the voltage follower A and then is sent to the input end of the digital display head to display the control temperature value. Adjust the potentiometer W2, and the value displayed on the digital display head will change accordingly. The temperature value displayed is the control temperature value. Potentiometer W1 is for pre-control temperature adjustment, its voltage adjustment range is 0-0.27V, and the corresponding adjustable temperature range is 0-27℃. After this potentiometer is adjusted, the voltage of its intermediate head and the voltage of the intermediate head of potentiometer W2 are respectively sent to the inverting and non-inverting input terminals of comparison amplifier B (amplification factor is 1). The voltage at the output terminal of B is the difference between the two input voltages. This voltage corresponds to the difference between the two set temperature values. For example, adjust W1 to 0.10V, corresponding to a temperature of 10°C; adjust W to 0.80V, corresponding to a temperature of 80°C. The output voltage of B is 0.70V, which means the temperature is 70℃. This voltage and the voltage output by the integrated temperature sensor are sent to the voltage comparator C for voltage comparison. When the voltage output by LM35 is less than the output voltage of B, C outputs high voltage, and the thyristor T1 is always turned on due to the bias current. AC 220V is directly applied to both ends of the electric heating element for high-power rapid heating. When the voltage output by LM35 is greater than the output voltage of B but less than the output voltage of A, it indicates that the actual temperature is close to the control temperature, C outputs low voltage, thyristor T1 is in a cut-off state due to no bias current, and voltage comparator D outputs high voltage. flat, the thyristor T2 is still in the conducting state, and AC 220V needs to be applied to both ends of the electric heating element through the diode D2 for low-power slow heating (the heating power at this time is only 25% of the original). When the actual temperature rises above 80℃, the output voltage of LM35 is greater than 0.80V, the voltage comparator D outputs low level, the thyristor T2 is also cut off, and the electric heating element is powered off. Due to the small heating power at this time and the heat dissipation effect, the temperature will not rise significantly. The actual temperature fluctuates within a small range around the control temperature, thus achieving high-precision automatic control of the temperature. 2. In use Notes 1. Switch K is in the 2 position when setting the control temperature, and is in the 1 position during normal heating control. The digital display head displays the actual temperature value; 2. Potentiometers W1 and W2 can use ordinary organic solid core potentiometers. Potentiometer W2 can use multi-turn tape indicating precision potentiometers and be installed on the panel for separate adjustment; 3. For thyristors T1 and T2, choose bidirectional thyristors with a withstand voltage of 220V and a current greater than the actual working current, and add heat sinks to dissipate heat during use to prevent overheating damage; 4. The current of D2 can be greater than half of the actual working current. , and add additional heat dissipation device; 5. One end of the thyristor is connected to the ground wire of the control circuit, so the entire circuit has AC mains power. During installation and use, isolation and insulation measures should be taken to prevent electric shock; 6. The adjustment of W1 should be appropriately selected according to the actual heating situation.