How to Lengthen the Flash of an LED Flasher

Lengthen the time between flashes with the flash rate resistor.

LED flashers sometimes flash too fast or flash so fast they appear as if they are always on. By lengthening the time between flashes, you slow down the flash rate. Once you locate the timing resistor, you change its value to meet your requirements.

Instructions

1. Obtain the schematic of your Flasher LED circuit. Examine the components on it and determine which resistor(the "timing resistor") controls the flash rate. Check on the schematic to see if the timing resistor or "flash rate" resistor are marked as such. Contact the designer or manufacturer of the circuit to find out the location of the timing resistor if you can not locate it yourself.

2. Multiply the value of the timing resistor by two to obtain the value of the timing resistor that will double the length of the LED flasher.

3. Disconnect the power to the LED Flasher circuit. Measure the voltage levels on each of the components and discharge any charged components (such as high voltage capacitors) if you are working with a circuit that can store dangerous levels of electrical current.

4. Remove the timing resistor from the circuit and replace it with a resistor that has twice its resistance value.

5. Turn on the LED flasher and observe that the time between flashes has been lengthened. Increase the value of the timing resistor if the time between flashes has not increased enough. Reduce the value of the timing resistor if the time between flashes has decreased.

Tips & Warnings

• Different types of LED flasher circuits are designed differently. Although one resistor can be used to control the frequency of the flashes, changing this resistor will change the duty cycle of the flash. This will sometimes limit the range of the timing resistor you can use. And that's because the "on time" of the pulse might not meet the LED's minimum pulse width specification.

• Improper use of electronic equipment and components can result in fire, serious injury or death. Always work under the supervision of a safety certified electronic technician or electronic engineer. Obtain a electronic safety certificate before you work with electronic equipment and components.

References

• LEDLight; Electronic LED Flasher EP29
• Wild-Bohemian; Simple LED Flasher Circuits
• MotorcylceGear; Targa LED Flash Controller Resistor (Pair)

Resources

• Hobby Projects; Flasher & Blinkers / Light Flashing Circuits
• Techlib; Flasher Circuits
• Totus Terra; 555 Timer Oscillator Frequency Calculator
• Doctronics; 555 Timer