You can add this high-efficiency dimming and flashing circuit to an existing battery-powered lantern or flashlight or to a custom design. For the car it makes a great lamp for changing a flat tire, back seat reading or emergency engine work. The flasher mode is useful for warning other drivers of your troubles and it may be adjusted to have a very short flash duration for long-term use as when the car must be left on the shoulder overnight.
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This is a simple circuit for sequentially flashing Christmas light strings or other similar low-power lamps. The socket symbols may be single bulbs or sockets for lamp strings. The load must be capable of operating from DC since the SCRs rectify the line voltage.source

When you driving a car if there are times when a little light inside the car would greatly assist one of the passengers but the dome light is too bright for safe driving. This dimmer circuit may be added to an existing dome light or included with a new passenger spot lamp.The lamp is dim when the potentiometer is set near the higher voltage.source

Here is a simple circuit for sequentially flashing Christmas light strings or other similar low-power lamps. The load must be capable of operating from DC since the SCRs rectify the line voltage. The SCRs must be sensitive-gate types and must be able to handle the load current and line voltage. source

This circuit will generate signal to flashing the small lamp about every 1 second.The flashing rate control by adjust R1.The rate voltage of the lamp depend on the main power supply.This circuit can apply to use with other light source such 12V bulb,group of series/parallel LEDs or alter to relay to drive a high voltage loads.source