Medical call with lighting signal receiver circuit diagram

As shown in FIG receiver may help patients avoid missing voice in the daytime, only the receiver itself is working, lights will automatically cut off part. At night the lightin
Medical call with lighting signal receiver circuit diagram - schematic

g signal receiver and simultaneously sent with the patients request. Call switch is pressed, and also the primary transformer X1 AC power is turned on, the secondary voltage is rectified, filtered, the output DC voltage by R1 to the VT1 collector. If during the day, due to exposure to light, the photosensitive resistor LDR1 low resistance state, VT1 conduction, its collector is pulled to ground potential, the thyristor BT136 does not work, then only call ringtone can be heard, the lighting signal is inactive. At night, LDR1 due to darkness and high-impedance state, so after pressing S1, VT1 off, the positive DC voltage filtered R1 and R3 may be charged to dawn. VD3 effect allows a constant positive DC bias trigger BT136, so that the incandescent lamp L1 light, so ask at night can hear the bell, but also to see the lighting signal for help. Zener diode ZD1 is used to limit the voltage across C2 is maintained at a stable value set. A, point B on the right side of the circuit section can be replaced at the circuit of Figure, but with the relay to control lighting without thyristors. During the day, due to the low resistance LDR2 bypass the base current to VT2 VT2 end, the relay RL1 is not working. In the evening, LDR2 was almost an open state, the base current through VR1, R4 and R5 flows into the base so that VT1 conduction, RL1 pull bulb L2 light.


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