A power-saving and energy-saving heater control circuit

At present, commercially available heaters have only two types of adjustment: 500W and 1000W, and they are all in a continuous heating state. In this way, when it is not too cold, you will feel overheated when using 1000W for heating, and feel that the heat is not enough when using 500W for heating.

1. Heater control circuit function
This circuit has the following functions:

1. The heater can be put into intermittent working state, that is, heating for a period of time and stopping for a period of time. In this way, it can save electricity and meet people's heating needs.

2. It has a long-term (more than 10 hours) timing function. Just set the timing time before going to bed, and the AC power of the heater will be automatically cut off at that time.

2. Composition of the heater control circuit
The control circuit block diagram is shown in the figure above. As can be seen from the figure above, the circuit is mainly composed of a timing circuit, a first monostable circuit control circuit 1, a second monostable circuit control circuit 2, an optocoupler controllable circuit, an electronic switch, and a power supply circuit.

The DC 5.4V power supply circuit is composed of CI, R1, Zener diode DW, rectifier diode D1, capacitor C2 and C3, etc., which supplies power to the entire circuit. IC1, R2, R3, C4, C5, C6, D2, D3, T1, WI and reset button K2 form the timing circuit. IC2, R4, R5, R6, C7, C8, C9, D4, T2 and potentiometer W2 form the first monostable circuit. R8 and T3 form the control circuit 1.

The second monostable circuit is composed of IC3, R9, R10, C10, C11, D5, D6, T4 and potentiometer W3.

Rll, R12, R13, T5, T6 etc. constitute the control circuit 2.

IC4, R14, R15, light emitting diode LED2 and others form an optocoupler controllable circuit. Bidirectional thyristor BTA16A/600V and ceramic capacitor C12 form an electronic switch circuit.

3. Circuit working principle
The control circuit is shown in the figure below. Press the lock button K1. The DC power supply +5.4V voltage is established. Since the voltage across C4 cannot change suddenly, the ICI (2) pin is low level (<1/3VDD). Therefore, IC1 (3) pin outputs high level, and diode D3 is reverse biased to make IC2 (4) pin high potential, so it does not affect the operation of IC2's first monostable circuit. At the same time, the power supply 5.4V charges C6 and T1 through W1 and R3, so that the voltage of ICI (6) and (7) pins continues to rise, and the timing starts. Since the voltage across C7 cannot change suddenly, the IC2 (2) pin is low level, so IC2 (3) pin outputs high level. This high level: First, the optocoupler thyristor IC4 is turned on, the main thyristor BTA obtains the trigger current and turns on, the heater socket is powered, the heater heats up, and the light-emitting diode LED2 lights up. Secondly, the transistor T3 is saturated and turned on, that is, the IC3(2) pin is at a low level, so the IC3(3) pin outputs a high level. Due to the action of diode D6, the voltage of IC3(6) and (7) pins is clamped to about 0.5V, and capacitor Cll cannot be charged. The high level output by IC3(3) pin makes the transistor T5 saturated and turned on, T6 is cut off, and the power supply 5.4V charges capacitor C7 through resistor R4. After about 0.7R4C7≈330ms, it is charged to the power supply voltage of 5.4V. At the same time, the power supply 5.4V charges C9 and T2 through W2. Due to the existence of T2, the charging time is extended by β times (β is the amplification factor of T2). The voltage of IC2(6) and (7) pins continues to rise.

When the voltage rises to >2/3VDD, IC2 (3) pin outputs a low level. First, the optocoupler thyristor IC4 is turned off, the main thyristor BTA is also turned off, the heater socket loses power, the heater stops heating, and LED2 goes out. At the same time, C9 is quickly discharged through IC2 (7) pin and D4 to prepare for the next charge. Second, T3 is turned off. D6 is reverse biased, and the power supply 5.4V starts to charge Cll and T4 through W3 and Rl0. The voltage of IC3 (6) and (7) pins continues to rise. When it rises to >2/3VDD, IC3 (3) pin outputs a low level, turning off T5 and turning on T6. At this time, the voltage originally charged by C7 is quickly discharged through T6, causing the voltage of IC2 (2) pin to drop rapidly. When the voltage of (2) pin drops to <1/3VDD, the first monostable formed by IC2 is set again. IC2 (3) pin outputs high level again, the heater heats up again, and the above process is repeated. Through the above analysis, it can be seen that the first monostable, the second monostable control circuit 1, the control circuit 2, etc. form a multi-vibrator circuit. The first monostable controls the heating time of the heater. By adjusting the potentiometer W2, the heating time can be adjusted. The second monostable controls the pause time of the heater. By adjusting the potentiometer W3, the pause time can be adjusted.

When the timing time is up, that is, when the voltage of ICI (6) and (7) pins rises to > 2/3 VDD, IC1 (3) pin outputs a low level and D3 conducts forward, so that the voltage of IC2 (4) pin is clamped at about 0.2V. Therefore, IC2 is forced to reset, so IC2 (3) pin outputs a low level, the optocoupler thyristor IC4 and the main thyristor BTA are cut off, the socket loses power, and the AC power supply of the heater is automatically cut off. At the same time, C6 discharges quickly through IC1 (7) pin and D2 to prepare for the next charge. The timing time can be adjusted by adjusting the potentiometer Wl (when Wl is adjusted to the minimum value, the timing time can reach 3 hours). When the reset button K2 is pressed, IC1 (3) pin outputs a high level again, and the oscillation circuit starts oscillating again.