Unexpected temporarily power cut often makes people is immersed in complete darkness in. It is hospital, theater or family no matter, this kind of circumstance needs the urgent lighting system that can start automatically. The urgent lighting light source of first selection is Bai Guang LED, one kind when serve as incandescent lamp compact and the substitute of tall effect, this product is getting popular () seeing a picture.
D1 and D2 realize the commutate to alternating voltage, d3 restricts gotten volts d.c. in 5V left and right sides. When communication power disappears, the voltage on M1 door (drop for 5V) normally 0 guide a M1, m1 delivers power to smooth detector part from batteries.
R2 is block of photoelectricity of sulfide of a kind of cadmium, in arrive from by day inside the brightness span of the night, this resistor goes to million Europe from change of 1000 Europe stage class. R1 is used at adjusting brightness threshold value. When the light is dim, u2 outputs logistic tall n and to the timer part power supply that is based on U3. U3 guides a M2 and M3, m2 and M3 guide an U1 and LED.
In the meantime, electric direction C1 charges. When the voltage on C1 achieves VCC/2, timer is stopped and close M2 to shut LED then in order to save batteries energy. If C1 is 100µF, this LED maintains 10 minutes about after black day power cut, if do not hope,can connect LED through closing S1 will guide in a limited time.
When normal power supply the discharge leakage current of batteries is 1µA about. The capacity of typical AA date batteries is 2000mA hour about, to bide his time when 1µA in leak electric current time exceeds 200 years. In power cut and during the work that timer already stopped, the R1-R2 that shows to the place in the graph is numeric, wait for machine electric current to be 7µA about, although press this leak to lead computation, bide one's time life also exceeds typical batteries 10 years 3 times of storage life. Drag extraction electricity to be 6µA about from alternating current source, perhaps say, the electric current below 120V alternating voltage under 1mW, and drag extraction electricity to be 100mA(to guide when LED about from batteries the) when connecting. (origin: Chinese lamp acts the role of a website)