How to Make Your Own LED Strobe

You can make a simple strobe with bright white LEDs.

In 2010, a new generation of high-brightness white light-emitting diodes, or LEDs, is available to electronics hobbyists. You can build a strobe light with a simple circuit based on the 555 timer IC and a few of these LEDs. While the light is not as powerful as that from a xenon flash lamp, you can still do stroboscope-type effects in a darkened room. A key part of this design centers on the 555 circuit's timing. The LEDs must flash quickly to capture motion, but not so quickly that they compromise brightness.

Things You'll Need

• 5mm high brightness white LEDs, 3
• 555 timer IC
• 1N4148 diode
• 10K ohm ¼ watt resistor, 2
• 1K ohm ¼ watt resistor
• 180 ohm ¼ watt resistor
• Microfarad 50V capacitor, 1
• .1 microfarad 50V capacitor, 2
• 10-volt DC power supply
• Square wave oscillator
• Prototype breadboard
• Assorted lengths #22 solid jumper wire

Instructions

1. Align the 555 timer IC on the breadboard so its pins straddle the slot in the middle of the main connection area. Make sure the notch in the IC package faces to your left. Press the IC gently into the board, making sure the pins go in straight.

2. Slip one lead of the 1K ohm resistor into the breadboard so it connects to pin 7 of the IC. Slip the other lead so it connects to pin 4. Insert a 2 inch jumper wire so it connects pin 4 to pin 8. Insert another 2 inch wire so it connects pin 7 to pin 6. Slip one lead of the 1 microfarad capacitor into the board so it connect to the IC's pin 1. Insert the other lead so it connects to pin 6. The 1K resistor and 1 microfarad capacitor together set the 555 timer's 1.1 millisecond "on" time.

3. Inspect the LEDs. The 5mm standard LED has a flat spot on its body, indicating the diode's cathode side. The 1N4148 diode has a stripe near the cathode lead.

4. Insert the 1N4148 diode's cathode lead so it connects to pin 4. Insert its other lead so it connects to pin 2. Slip one lead of a 10K resistor in the board so it connects to the IC's pin 4. Slip the other lead so it connects to pin 2.

5. Slip one lead of the remaining 10K resistor so it connects to pin 4. Slip the other lead into an unused column on the breadboard. Insert one lead of a .1 microfarad capacitor so it shares the column with the 10K resistor lead you just put in. Insert the capacitor's other lead so it connects to pin 2. Insert a jumper wire at least 1 foot long so it shares the column with the capacitor and resistor. Connect the other end to the square wave oscillator.

6. Insert the free end of a jumper wire at least 8 inches long so it shares the same column as the .1 microfarad capacitor and 10K resistor from step 5. Insert one lead of the 180 ohm resistor so it connects to pin 3. Insert the other lead into an unused column. Insert the anode leads of all three LEDs to they share the same column as the 180 ohm resistor. Insert the cathode leads so they all share an unused column. Insert one end of a 3 inch jumper wire so it connects to the shared cathode column. Insert the other end so it connects to pin 1.

7. Insert one lead of the remaining .1 microfarad capacitor so it connects to the IC's pin 5. Insert the remaining lead so it connects to pin 1. Insert 2 jumper wires at least 1 foot long so they connect to pin 1. Connect the other end of one to the grounding terminal of the 10-volt DC power supply. Connect the free end of the other to the grounding terminal of the oscillator. Insert another long jumper wire so it connects to pin 8. Connect the other end to the positive power supply terminal.

8. Turn the power supply on. Turn the square wave oscillator on. Set the oscillator's frequency to about 1Hz. The LEDs should be flashing about once per second. You can turn the frequency up to about 1,000Hz and the LEDs will strobe at the same rate.

References

• Doctronics: 555 Timer
• Electronics Club: Light Emitting Diodes

Resources

• Read this Article in Spanish