This circuit uses a dual op-amp IC LM358 and two transistors. It can be powered by a 6V maintenance-free rechargeable battery or a lead-acid accumulator type battery. It has two modes of operation: flasher mode and dimmer mode. The dimmer mode helps conserve the battery power, while in flasher mode the lantern can be used as a beacon.
The first op-amp (N1) is wired such that it generates pulses at a constant frequency. The second op-amp (N2) acts as a comparator, while transistors T1 and T2 form a complementary pair to drive the lamp. When switch S2 is open, the circuit is in dimmer mode.
The intensity of the lantern can be changed by varying the pulsewidth with the help of potmeter VR1, which controls the reference voltage at the inverting pin of comparator N2, and hence the pulsewidth at the comparator output to control the lamp intensity.
When switch S2 is closed, the circuit functions in flasher/beacon mode. The flashing rate of the bulb can be varied with the help of potmeter VR1.
Assemble the circuit on a general-purpose PCB and then connect the 6V battery along with power ‘on’/‘off’ switch S1. Now place this gadget at a suitable place in your house.
If both switches S1 and S2 are closed, the bulb flashes at a frequency selected by adjusting potmeter VR1. If switch S2 is open, the bulb glows continuously.