Summary of HIGH POWER LED FLASHING BEACON USES A SWITCHING REGULATOR
This article describes a portable high-power LED flasher circuit using an MC34063 switching regulator. Powered by 6V or 12V SLA batteries, it drives a 1W white LED at approximately 5% duty cycle with a flashing rate of 4 Hz. The circuit limits current to 350 mA via a sense resistor and timing capacitor, making it suitable for distress signals or directional beacons in various locations.
Parts used in the High Power LED Flashing Beacon:
- MC34063 monolithic switching regulator
- 1 W power LED
- 6 V or 12 V SLA lantern battery
- R1 (1 W sense resistor)
- C1 (timing capacitor, 100 µF)
This flasher/beacon circuit can be employed as a distress signal on highways, a direction pointer for parking lots, hospitals, and hotels, etc. The circuit uses a power LED, and provides more light than a typical incandescent lamp flasher. Use of a 6 V or 12 V SLA lantern battery makes the circuit portable.
The heart of the circuit is an MC34063 monolithic switching regulator subsystem, originally intended for use in DC-DC converters (Figure 1). This device contains a voltage reference, comparator, controlled duty cycle oscillator with an active peak current limit circuit, driver, and a high current output switch, all in an 8-pin DIP.
The circuit briefly flashes a 1 W power LED from a 6 V to 12 V DC supply – at about 5% duty-cycle (Figure 2). Current limiting to the LED is accomplished by monitoring the voltage drop across R1, a 1 W sense resistor placed between VCC and the output switch, pin 1.
The maximum current capability of a 1 W white LED is about 350 mA. At the beginning of a cycle, C1 starts to charge, and LED current rises rapidly, along with the drop across R1 which is monitored by the Ipk sense pin, IC1-7.
When this voltage becomes greater than 330 mV with respect to pin 6 (i.e., 330 mA), the current limit block in the IC provides additional current to charge the timing capacitor C1. This causes it to rapidly reach the upper oscillator threshold, at which point the output switch turns off and C1 discharges. Flashing rate can be altered by changing the value of C1. 100 µF gives approximately 4 Hz.
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- What is the primary application of this circuit?
The circuit can be employed as a distress signal on highways or a direction pointer for parking lots, hospitals, and hotels. - How does the brightness compare to typical flashers?
This circuit uses a power LED that provides more light than a typical incandescent lamp flasher. - Can this device be made portable?
Yes, use of a 6 V or 12 V SLA lantern battery makes the circuit portable. - What component acts as the heart of the circuit?
The heart of the circuit is an MC34063 monolithic switching regulator subsystem. - How is current limiting accomplished in this design?
Current limiting is accomplished by monitoring the voltage drop across R1, a 1 W sense resistor placed between VCC and the output switch. - What is the maximum current capability of the white LED used?
The maximum current capability of a 1 W white LED is about 350 mA. - How is the flashing rate altered in this circuit?
Flashing rate can be altered by changing the value of C1. - What is the approximate duty cycle of the LED flash?
The circuit briefly flashes the LED at about 5% duty cycle.
