Electric heating water dispenser circuit

(1) The power circuit is shown in Figure 1-31. The 220V AC power is stepped down by the capacitor G, half-wave rectified by VD1, filtered by G, current limited by the island, and
stabilized composed of a typical capacitor step-down circuit. When it is NE555 base circuit and the 'TX902 microwave induction controller provides a stable 12V DC voltage.
    (2) Principle of microwave induction remote control TX902 microwave induction controller contains a microprocessor, which uses the microwave Doppler effect to establish a micro-electric field in a certain space
. When a person or moving object enters the electric field, the echo will be reflected and passed through the electronic circuit. After mixing, a very weak moving frequency signal is detected
. After intelligent processing, this signal can output a control signal. The effective monitoring radius of TX902 is 1-7m. The main reason why pyroelectric sensors are not used here
is that they are convenient for modification, and pyroelectric sensors are particularly sensitive to heat sources and are prone to malfunction. The microwave induction control hoe only needs to be installed
on the side behind the plastic cage of the water dispenser for detection. It will not damage the appearance of the machine. The output terminal of TX902 adopts open-collector output. When the microwave
circuit detects someone moving within the monitoring range, the internal transistor is turned on for 1Os to discharge the charge on C3. The NE555 circuit forms a monostable
delay circuit. When pin ② is lower than 1/3 of the power supply voltage, pin ③ outputs high level, relay K is closed, SA1 turns on the heater for heating, and
the delay circuit composed of R2 and island delays The time is 3rrun, and the delay time is set relatively short. If people only pass by briefly, the water dispenser will automatically stop heating after 3 minutes. If there are always people in the room, TX902 will trigger the monostable circuit
multiple times within the delay time. When working, the water dispenser will continue to heat until it reaches the set temperature.     (3) Energy-saving improvements If you want to further improve the energy-saving effect, you need to make some small modifications to the heater of the water dispenser. The insulation measures for most water dispensers are very simple. They only use two pieces of preformed foam plastic to surround the heating tank, so the heat dissipates quickly. It is best to use polyurethane material for on-site foaming and filling around the heater. This treatment can ensure that there is no gap between the insulation material and the heater , reduce air flow, and greatly improve the insulation effect.