Lightning Activated Camera Shutter Trigger


Picture of Lightning
This picture was taken using the circuit.
Schematic

Description

This circuit is used to trigger a camera's electronic shutter circuit when a flash of lightning is present. It has been suggested that this circuit would also work to photograph fireworks displays, I have never tried that, but in theory, it should work.

The photodarlington should be set up to either look through the camera's viewfinder or a small black tube that gives the same view as the camera's lens. With an SLR camera, this circuit should only be used at night, daytime use will cause it to retrigger indefinitely because the viewfinder goes black then light when the photo is done, this restarts the detector.

The photodarlington is a QT semiconductor model QT-L14R1, available from Digi-key. The VN10KM is an N channel mosfet transistor, a more common IRF520 would probably work here, but I have not tried it. Digi-key also sells the VN10KM. If you get any good shots with this circuit, I would love to see them.

Theory

In a nutshell, the photo darlington converts light pulses into electrical pulses, the first LM324 section amplifies the electrical pulses, the second LM324 section is a high pass filter that only passes quick changes (lightning). The third LM324 stage is a comparator that allows only large pulses to pass through, and the 4047 one-shot stretches out the length of the pulses so that they are long enough to drive the relay and trigger the camera.

The 2N3904 drives the reed relay, and the VN10KM prevents the circuit from triggering when it is first turned on. The LM324 GND Ref circuit provides a reference voltage at 1/2 of the 9V battery for use in the other op-amp circuits. That's about it.

Lightning Detector in GIF format (17kb)

Lightning Detector in PostScript format (93kb)

lightning web ring for lots of lightning stuff.

Here are more lightning pictures taken by someone who used a modified version of this circuit.

Digi-Key for parts.


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