Touch desk lamp circuit

(1) Working principle The appearance and circuit of the touch table lamp are shown in Figure 16-18a-b. The left part of the circuit is the power circuit. After the 220V mains power
is stepped down by capacitor c1, iVD1-VD4 is rectified, filtered by C2, and stabilized by VD5, it outputs 10V DC voltage. The integrated block IC is a 555 time base circuit,
connected to a bistable working mode. When touching the wire A, the clutter signal induced by the human body is coupled into the circuit through the capacitor G. After rectification by VD6,
the ② pin of the IC gets a negative pressure. The ③ pin outputs a high level, the relay K is activated, and its contact K is closed. When the desk lamp is powered on, the desk lamp lights up; when the N electrode
is touched , the miscellaneous signal induced by the human body is rectified by VD7, so the ⑥ pin gets a positive Voltage, pin ③ outputs low level, relay K
is released, its contact K disconnects the desk lamp power circuit, and the desk lamp stops lighting.
    (2) Component selection In Figure 16-18b, general point contact diodes are used for VD6 and VD7. JRX-13F is used for the relay
, and the wire package resistance is about 300fl. The capacity of the bulb can be selected according to needs, but the contact capacity of K should be considered. NE555 is used for lC.
    (3) During production and installation, the printed board should be hidden in the base of the desk lamp, and the electrodes M and N should be replaced with chromium-plated copper sheets and embedded in a plexiglass plate
, or small metal animals or toys can be used as electrodes. The trigger pin ② is very sensitive, so the inverter M should be kept away from the AC power line 2. The circuit generally
works without adjustment. When in use, C- should be connected to the live wire end of the power supply.