Suddenly encountered a power outage the night, surrounded by dark … …. At this time, only you still lit a lamp, when you 1min (minutes) after the leisurely place lit candles, the light will slowly go out.
First, the working principle
Emergency lights short circuit shown in Figure 1. H is a low-voltage low-power cold cathode fluorescent lamp. When the circuit is connected to the grid after, 220V AC power by limiting resistors R1, crystal diode VD half-wave rectified, the voltage across the capacitor C charges up to 290V or so, while limiting resistor R2 through the fluorescent light tubes H. Power failure, the capacitor C will charge stored in R2 to continue to H through the power supply, so that delay brighten fluorescent tubes. After a period of time (approximately 1min), C at both ends of the discharge voltage dropped to 160V or so before the lamp automatically turns off.
Circuit, the lamp lit up the length of time delay and C the capacity and the size of the R2 resistance. When C = 330µF, the delay time up to 1.5min; increase the delay time may also increase the resistance R2, but with the R2 resistance increases, the lamp brightness will be significantly weakened.
Welding good emergency light circuit without any debugging can be put into use. Practice has proved that under the conditions of fluorescent lamps used in the DC voltage when the internal resistance of the coating over a pole shall be connected with the positive power supply, lamp starter so easy. If the fluorescent lamp does not light after power can be removed from the bayonet cap lamp, rotate 180 ° before inserting the cap can be.
Second, the component selection
H use of domestic low-voltage cold cathode fluorescent lamp 3W (shape see Figure 2). The tube from the inner tube and outer tubes, inner tube for the discharge, including the tube wall coated with a layer of opaque SnCI4 to replace the ballast resistor layer, including the phosphor coating the inner walls of pipes, different The light-emitting phosphors can have different colors. The most important feature of fluorescent tubes are: low voltage lighting, easy starter, power consumption, does not need ballast. For ease of installation, coupled with lighting circuit to be used for the lamp bayonet bantam caps.
1N4007-type silicon rectifier diode VD selection. C with a color TV power supply circuits commonly used 220µF, 400V electrolytic capacitor. R1 with RTX-1/2W carbon film resistors, R2 with RTX-1/4W carbon film resistors. XP polarized plug with a commercially available ordinary AC.
Third, the production and use
Short-term emergency light assembly as shown in Figure 2. In addition to fluorescent lamps and power plugs XP, the other components of all the welding in a confined with a small box made of thin wood (volume of about 65mm × 65mm × 35mm) inside. Dwarf fluorescent tubes bayonet caps by three wood screws used in the circuit box panel; XP 1m through the length of the double strand of soft plastic wire leads to the circuit box outside.