This is a digital display artificial intelligence temperature control circuit design
This is a temperature control circuit with simple artificial intelligence. When using this circuit for temperature control, simply switch the switch to the 2 position, set the control temperature, and pass the temperature value displayed by the 3-digit half-display head to accurately control the temperature, so that the temperature control operation becomes Very convenient. The LM35 is an integrated temperature sensor with an internal circuit calibrated. Its output voltage is proportional to Celsius temperature, linearity is good, sensitivity is high, and accuracy is moderate. Its output sensitivity is 10.0MV/°C with an accuracy of 0.5°C. Its measurement range is -55-150 °C. The self-heating effect is low at rest temperature. The working voltage is wide, it can work normally within the supply voltage range of 4-20V, and the consumption of the electrode is saved, and the working current is generally less than 60uA. The output impedance is low and is 0.1Ω at 1MA load. According to the output characteristics of the LM35, when the temperature is changed between 0 and 150 °C, the voltage corresponding to the output terminal is 0-150V. This voltage is divided by potentiometer W3 and sent to the detection signal input end of the 3-digit and half-digit display meter. When the voltage input to the input terminal is 150V, the displayed value is 150.0 by adjusting the potentiometer. The value displayed by the adjusted digital display head is the measured temperature value.
Temperature control selection can be achieved by potentiometer W2. By adjusting W2, the voltage of the middle head can be changed between 0 and 1.65V, and the corresponding control temperature range is 0-165 °C, which can fully meet the general heating needs. Put the switch K in the position of 2, the voltage in the middle of the potentiometer W2 passes through the voltage follower A and then sends it to the input terminal of the digital display to display the control temperature value. Adjust the potentiometer W2, the value displayed on the digital display head changes accordingly, and the displayed temperature value is the control temperature value. The potentiometer W1 is pre-controlled temperature regulation, and its voltage adjustment range is 0-0.27V, corresponding to the adjustable temperature range of 0-27 °C. After the potentiometer is adjusted, the voltage between the middle head and the middle head of the potentiometer W2 are respectively sent to the inverting and non-inverting input terminals of the comparison amplifier B, and the voltage at the output end of the 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 O.80V, corresponding to a temperature of 80 °C. The output voltage of B is 0.70V, which means the temperature is 70 °C. This voltage is supplied to the voltage comparator C for voltage comparison with the voltage output from the integrated temperature sensor.
When the output voltage of the LM35 is less than the output voltage of B, the C output is high, the thyristor T1 is turned on due to the bias current, and the AC 220V is directly applied to both ends of the heating element for high-power rapid heating. When the output voltage of the LM35 is greater than the output voltage of B and less than the output voltage of A, it indicates that the actual temperature is close to the control temperature, and the C output is low, and the thyristor T1 is in the off state due to no bias current. The voltage comparator D outputs a high level, the thyristor T2 is still in the on state, and the AC 220V needs to be applied to both ends of the 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 °C, the output voltage of the LM35 is greater than 0.80V, the voltage comparator D outputs a low level, the thyristor T2 is also turned off, and the heating element is powered off.
Temperature control selection can be achieved by potentiometer W2. By adjusting W2, the voltage of the middle head can be changed between 0 and 1.65V, and the corresponding control temperature range is 0-165 °C, which can fully meet the general heating needs. Put the switch K in the position of 2, the voltage in the middle of the potentiometer W2 passes through the voltage follower A and then sends it to the input terminal of the digital display to display the control temperature value. Adjust the potentiometer W2, the value displayed on the digital display head changes accordingly, and the displayed temperature value is the control temperature value. The potentiometer W1 is pre-controlled temperature regulation, and its voltage adjustment range is 0-0.27V, corresponding to the adjustable temperature range of 0-27 °C. After the potentiometer is adjusted, the voltage between the middle head and the middle head of the potentiometer W2 are respectively sent to the inverting and non-inverting input terminals of the comparison amplifier B, and the voltage at the output end of the 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 O.80V, corresponding to a temperature of 80 °C. The output voltage of B is 0.70V, which means the temperature is 70 °C. This voltage is supplied to the voltage comparator C for voltage comparison with the voltage output from the integrated temperature sensor.
When the output voltage of the LM35 is less than the output voltage of B, the C output is high, the thyristor T1 is turned on due to the bias current, and the AC 220V is directly applied to both ends of the heating element for high-power rapid heating. When the output voltage of the LM35 is greater than the output voltage of B and less than the output voltage of A, it indicates that the actual temperature is close to the control temperature, and the C output is low, and the thyristor T1 is in the off state due to no bias current. The voltage comparator D outputs a high level, the thyristor T2 is still in the on state, and the AC 220V needs to be applied to both ends of the 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 °C, the output voltage of the LM35 is greater than 0.80V, the voltage comparator D outputs a low level, the thyristor T2 is also turned off, and the heating element is powered off.
