Referring to the schematic of the proposed LEd emergency lamp circuit with infrared remote dimming feature, the design basically comprises of three stages: the infrared toggled 4017 sequencer, the LED dimmer using T2, and the automatic emergency switch using T3.
The IR sensor is a standard TSOP series IC configured with a BJT buffer T1 which amplifies the output from IRS sensor each time its toggled with an external IR remote transmitter, which could be simply your TV remote control handset .
The above switching response is appropriately applied at the clock input of the IC 4017 which is a Johnson divider counter chip and becomes responsible for generating a sequencing positive high shifts across its pin3 (start) to pin (11) and back to pin3 (repeat).
Each of he above 10 sequencing high outputs are terminated via 10 individual rectifier diodes and a series resistor. The resistors are calculated so as to generate a proportionately incrementing potential difference at the base of T2 with reference to the value of the resistor set by VR1 across the base and ground of T2.
Depending upon which output of the IC4017 may be high at any given instant, the connected LED brightness is determined according to this selected output (toggled via the IR stage and the remote handset). At pin3 the illumination may be the highest while at pin11 it could set to produce the minimum brightness over the attached LED.
T3 is positioned to invert its collector voltage in response to the input at its base acquired from an external AC to DC 5V adapter unit.
As soon as this supply is removed or fails, T3 switches ON via R5 allowing the required battery voltage to reach the collector of T2, which in turn passes it on to the LED connected across its emitter/ground terminals with the required amount of glow as determined by the specific output of the IC 4017 at that instant selected to be high by the user using the IR remote control facility.
Parts list for the above IR controlled LED emergency lamp with dimmer circuit
R6—R15 = 200 ohms to 2K (proportionately incremented)
C2 = 47uF/25V