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Programmable Time Delay Flash Trigger

Want to try your hand at 'stop motion' photography, where dynamic events such as a match bursting into flame, a drop splashing into a container of liquid or a projectile passing through a light globe, are captured at a crucial moment? Here's a project designed specifically for this kind of work. It lets you trigger your electronic flash at the precise moment for a great picture.

by Jim Rowe

Specifications

Trigger inputs: electret microphone or external trigger (via PIR sensor etc)

Delay time: 0 to 999ms in 1ms increments or
0 to 9.99 seconds in 10ms increments

Timing Accuracy: 1ms or 10ms

Outputs: (1) Non-delayed triggering for external shutter release
(2) Delayed triggering for electronic flash

Power: 9V alkaline battery

Consumption: 16mA (standby); 30mA when triggered.

Have you been intrigued by those impressive photos capturing the crown-shaped splash when a drop falls into a dish of milk or the tip of a chameleon’s tongue when it’s attaching itself to a flying insect? Or a light bulb shattering as a bullet enters it? These are the kinds of shots which can be achieved using ‘stop motion’ photography.

You don’t need much gear to take these shots. The main requirement is a camera with a very fast shutter speed or an electronic flash. 

Either way you need an electronic triggering unit to either open the camera shutter release, or fire the flash automatically in response to a reference event – such as a sound (like a ‘bang’ or ‘click’) or a contact closure (like the contacts in a PIR motion sensor).

Click for larger image
Who let the smoke out? 30ms after we smashed the light globe by hitting it with a metal weight (that’s it on the right) the filament is only now starting to realise it's lost half of its bulb and is starting to burn up, with flame and smoke. This is a combined time exposure (hence the warm glow from the lamp) and flash shot using the delayed trigger (hence the white pieces of glass). Believe it or not, this was the first shot we took – and a dozen light globes later, we decided it was the best!

The electronic triggering unit must have an accurately adjustable delay time. This allows you to set the camera or flash triggering to occur not just automatically in response to the reference event, but a known period of time after it. 

So if you predict that the crucial event you want to capture occurs about 40ms (milliseconds) after the reference event (eg, the bang or click, or contact closure), you can set the triggering delay to 40ms and see if this gets the shot. If it then turns out that the shot was a little early or late, you can either reduce or increase the delay to get the precise result.

So that’s the rationale behind this project. It’s an automatic electronic shutter release/flash trigger unit with a delay time which can be adjusted in 1ms steps from 0 to 999ms or alternatively, in 10ms steps from 0 to 9.99 seconds.

Triggering can be from an electret microphone (to pick up sound ‘events’) or other devices like a PIR (passive infrared) motion sensor, light-beam interrupter system, or custom sensor switches such as microswitches attached to machinery.

It is housed in plastic case which on the front panel (lid of case) has three rotary switches to set the time delay, a sensitivity control for the microphone/preamp, an “arm”  button, toggle switches to turn on power and to select the time delay, a red LED to show that the unit has been triggered and a green LED to show that the flash or shutter has been fired. 

Along the top side of the case are four sockets which connect an electret microphone, an external trigger (eg, PIR sensor), the electronic flash and, if required, the electronic camera shutter.

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