Two-way touch switch 4

  
After the power is turned on, 220V AC by the step-down transformer T, VDI ~ VD4 bridge rectifier and Cl filtered output of about 10V DC voltage for the Darlington circuit and s
Two-way touch switch 4 - schematic

witch power relay control circuit. Darlington VTI and VT2 are in cut-off state only, two relays normally open contacts K kl and k2 are open, lights H does not shine. Turn on the lights, press a finger pressure at the electrode pad M2, the DC voltage to VT2, inject a base current through resistor finger and R2. VT2 conduction, the relay K is energized, contacts kl, k2 is closed, wherein k2 lamp is turned on the lamp H H circuit is energized luminous, kl resistor R3 is connected to the circuit so that the circuit self-locking, so that when the finger from the M2, since R3 access relay status remains suction units, lamps H is always light. When the light on, as long as the lower electrode sheet with your fingers Ml. At this time Darlington VTI rapidly saturated conduction, so that the base potential due to VT2 down to zero and turned off, de-energized relay K release, its normally open contact kl, k2 jump, put out the light H off.




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