Improvement of household electric blanket control switch

Probe domestic switch needle KG-300K needle head diameter is 3.0mm normally open switch needle

DFN1006 TP-RCLAMP3321P ESD Diode Low Capacitance

MOS power IC full range

Household electric blankets only have high and low temperature gears, and low temperature gears usually use diodes for half-wave rectification, so that the low temperature gear power is about one-half of the high temperature gear. However, in the case of severe winter use, the temperature of the high temperature file is often too high, and the temperature of the low temperature file is too low. When the weather is slightly warmer, the temperature of the low temperature file is too high. In this regard, I used a common thyristor thermostat circuit to make a multi-speed thermostat switch, as shown.

Circuit principle: This circuit is a typical thyristor thermostat circuit. When the voltage gradually rises after the sinusoidal alternating current crosses zero, the capacitor C is charged through R1 and R. When the charging voltage across the capacitor is greater than the breakdown of the bidirectional trigger tube DB3. When the voltage is applied, DB3 is turned on, and the trigger voltage is applied to the control electrode of the thyristor SCR. After the thyristor is turned on, the control electrode loses its effect, and the thyristor will remain in the on state until the AC mains supply crosses zero again. . Different switches are connected to the circuit through the switch K, so that the charging time is different, the conduction time of the thyristor is also different, and the voltage applied to the load RL is different, thereby obtaining different powers.

Component selection: Switch K utilizes a voltage selection switch in a conventional 3 to 12V DC power supply available at hand. The values ​​of the resistors used in the experiment are 1k, 18k, 27k, 39k, 51k, 100k. As shown in the figure, the corresponding powers are P, 5/6P, 4/6P, 3/6P, 2/6P, 1/6P. If you do not have this switch, you can also use other multi-function switches. For example, if you want to change to 5/5P, 4/5P, 3/5P, 2/5P, 1/5P, you need to change the resistance value. All resistors use 1/8W carbon film resistors, and the capacitor's withstand voltage should be greater than 150V. If the capacity is changed, the resistance values ​​of the six resistors connected to switch K also need to be modified. The thyristor SCR uses BCR3AM, but it can also be modified according to the existing thyristor at hand. VT1 uses DB3 bidirectional trigger tube. If not, it can also be replaced by two circuits on the right side of Figure 1: Circuit 2 uses two 9013 CE junctions in series, and circuit three uses the manifold as a power indicator. Directly substitute the substitute circuit into the a and b ends of the circuit.