Double button light switch circuit (3)

It is a double-button touch clam switch made of Darlington tube. The circuit feature is that the touch chip is
isolated from the 20V AC mains power through the T phase of the power transformer, which is relatively safe.
    After the circuit is powered on, the 2p OV AC power selector transformer T steps down, VDl-VD4 bridge rectifier and C. Filter and
transmit about 10V DC voltage to supply power to
Darlington switch circuit and relay
control circuit. The Darlington tubes
VT1 and VT2 are both in the cut-off state
, the two moving contacts
kl and k-2 of the relay K are both open, the lamp
finger presses the electrode piece M2, and the DC voltage passes through the finger iL and 』^ VT2 is connected to the base current, VT2
is turned on, relay K is slowed down, and contacts k1 and k2 are closed. Film 1. k-2 makes the electric lamp F emit light, and k1
turns the resistor R on. Connecting the circuit makes the circuit self-locking. When the finger leaves M2, due to R, WJ is connected. The relay
can still maintain the pull-in state, and the spider will always light up. When you need to turn off the light suddenly, you only need to press the power switch
M1 with your finger. At this time, the Darlington tube VT1 quickly saturates and conducts, causing the potential transfer potential of VT2 to drop to zero and the cut-off
relay K is released, and its moving contact k J, k2 jumps 30． IU light E goes out.
    VT1 and VT2 need to use u850 Darlington diodes with extremely high amplification ratio. If the reader cannot find such
tubes, two 001 4-type silicon NI and N diodes with a multiple of 200 can be used to form a composite tube. To replace the Darlington
tube. K is best to use JZC-22F, 2200 type ultra-small power relay, which has two sets of switching contacts, the contact
capacity is 2A, and the line package r operating voltage is OV . Tahacichuan 220V/9V, 5VA small power inverter.
The touch electrode sheet can be cut into a 2-cent coin-sized piece with a tin can, and then cut from the center with a spacing of about
1n, tr. left and right, and then paste it on the plastic shell.