Strobes are useful devices for seeing fast moving components freeze or just as lighting effects. Unfortunately for a really good result you need to use a Xenon flash tube which can produce intense brief discharges of light but it needs high trigger voltages - upwards of 4KV!

However with LED technology moving on quite quickly nowadays, a simple and fairly effective strobe can be built from high power white LEDs.

Signal at the collector of Q2 which drives Q3

Download circuit simulation - Livewire

The waveform shows the . The output pulses are kept at about 80ms while the space between them can be varied from 80ms to about 400ms using VR1 which alters the charge time of C2. The "on" time stays constant and produces a fairly brief pulse for the LEDs.

The current through the 8 LEDs is about 100mA each with a 4.7ohm resistor but since the pulses are brief, even when tested with a supply of 12 volts, the Darlington only got warm and the LEDs coped fine..

VR1 is mounted directly to the PCB to create a neat module with only 2 wires for the supply.

DOWNLOADS

• Strobe PCB as jpg - you'll have to resize it

This time 38 LEDs were connected except this time, pairs of LEDs were wired in series and then paralleled up to make 19 pairs. This increases the voltage drop all were wired 2 were placed in series to prevent large power loss in the LEDs resistor.

The supply was 12v this time and the LED resistor was reduced to 0.47ohms. The result was fairly impressive but no where near the power of a mains strobe. However, some experiments such as a slow running tap produced some interesting images, as well as spinning wheels on motors, making them appear still.

DOWNLOADS

• Strobe 2 PCB as jpg - you'll have to resize it
• Strobe & Strobe 2 PCBs on PCB Wizard
• LED PCB on PCB Wizard