This is a circuit for a flashing beacon that uses a LM317T to flash a bulb at the rate of 4 cycles per second. -- Ashok K. Doctor


A flashing beacon has many uses. It can be employed as a distress signal on highways or as a direction pointer for parking lots, hospitals, hotels, etc. Here we present a flashing beacon that uses well-known regulator IC LM317T. As LM317T regulator can deliver more than 1 amp. A small 12V, 10W bulb with a high-quality reflector can serve as a good visible blinker.


A 12-15V, 1A DC supply is connected to the input pin of the IC. A 12V, 10W bulb and a combination of resistors and capacitors are connected between the output pin and ADJ pin of the IC as shown in the figure. The IC is provided with an aluminium heat-sink to dissipate the heat generated while delivering full current. Since the IC has an inbuilt switch-on current limiter, it extends the bulb life.

For the shown values of resistors and capacitors, the bulb flashes at approximately 4 cycles per second. The number of flashes depends on the charge-discharge time of the capacitors. Different values of resistors and capacitors can be used to increase or decrease the number of flashes.


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