STOP MOTION ANIMATION, THE EASY WAY

Stop motion animation, one of the oldest special effects, makes the impossible seem real. But the tedious process — move the model, take a picture, repeat thousands of times — discourages citizen film makers with non-obsessive patience levels.

I recently discovered iStopMotion, Mac software that automates the process and works with any camera that can capture QuickTime. iStopMotion features a transparent preview that lets you superimpose the previous frame over the current one before you shoot. This alone helps enormously. The Time Lapse feature shoots frames continuously at a specified interval, and Speech Recognition lets you say “Capture” instead of having to click. These two features saved me thousands of trips back to the keyboard and mouse, and in just a few minutes of experimenting, I made a fairly impressive little flick.

You can even shoot frames simultaneously from multiple cameras, to create seamless cuts between different angles, just like the pros.

For inspiration, go watch King Kong and visit the example pages. I’ll post my animation on the media. If you create one, let us know!

Kite aerial photography is a fun hobby for engineers and artists alike, and the resulting images can be beautiful. However, one unlucky gust can send your camera tumbling to the ground. That’s why disposable cameras are a good choice for beginners. Their low cost means there’s no big loss if they crash. They’re also lightweight, and most are pre-focused to infinity, which means they’re good for taking scenery shots.

Many rigs have been designed to take film-based disposable cameras aloft.

But film disposables require winding between shots, so you can only take one picture per launch.

Fortunately, there are digital equivalents that use electronic switches and need no winding. I use the Dakota Digital PV2; it’s $19 at Camera and Wolf Camera (camera.com), with a $10, non-LCD version available in CVS stores. The PV2 holds 25 photos. As with a film disposable, you send it away for processing.

Here’s how to make a kite-ready timer circuit that triggers the PV2 once per minute, after an initial delay. You can also adapt it to trigger other, non-disposable cams.

Since it takes time to launch the kite, we’ll want to delay the first shot. We’ll implement this with a simple resistor-capacitor network. The capacitor slowly charges through a resistor until its voltage is high enough to turn on the timer chip, via the chip’s reset pin.

The PV2 automatically shuts off after 3Vz minutes idle, so our delay must be less than this. The time depends on the relative values for the resistor and capacitor, and I calculated that a 470pF capacitor and 680k0hm resistor (C2 and R3 in schematic at right) would produce about a 3-minute delay. Try this combination, and if the camera shuts off before having a chance to fire, reduce the resistor value.

For the main part of our circuit, we’ll use a TLC555 or LMC555 timer chip. Configured with two resistors and a capacitor, 555 chips can generate square waves of almost any frequency up to 2MHz. We want to make ours oscillate every minute, firing a shot once per cycle.

Timing a 555 also uses an RC (resistor- capacitor) network. In our configuration, the 555 discharges a capacitor through one resistor and recharges it through two resistors in series. While the capacitor charges, voltage on the timer’s output pin is high (3V) — and it’s low while it discharges. I determined that a JF capacitor (Cl in schematic) and two 680k0hm resistors would tune the 555 to produce a 60-second square wave. (See website noted earlier for derivation.)

Other components in the circuit are an indicator LED that flashes once per cycle (for testing), and a diode between the Output and Reset lines. This keeps the Reset line voltage high, which protects against noise from the camera’s flash that can trigger the shutter accidentally.

Take the batteries out, remove the three screws that hold the body together, and take off the back cover, being careful not to touch any of the electronics inside (they may be at high voltage).

Carefully hold the main PC board as shown on page 130, making sure the vise or jaws don’t short any exposed components. The huge capacitor carries the flash bulb charge, and it must be discharged before any hacking. Hold a flathead screwdriver by the plastic handle, and touch its tip to both capacitor leads simultaneously. There will be a large pop and flash as it discharges. (Do this again after any time the board has sat idle.)

Cut three wires in red, black, and yellow (or other color) for the shutter wire. Solder these to the pins located where the top shutter board connects to the front flash board. Don’t try to close the case all the way.

Before soldering your circuit onto the board, you should test it out on a breadboard. Build the circuit following the schematic on page 131, making sure to place all the capacitors, diodes, and LEDs in the proper directions.

Connect the red and black wires from the camera to the points on the circuit, respectively. The LED should light up after two minutes or so, and then cycle on and off about every minute. Use a multimeter to confirm that there are 3V between the red and black wires, and check the voltage across the 470JJF capacitor (C2) to make sure it rises slowly to IV or so, then jumps up to 3V. Check the 47JJF cap (Cl) and look for slowly oscillating voltage between IV and 2V. Finally, check the output voltage, which should flip between OV and 2V, following the LED. If you’re prototyping your circuit on a breadboard and it all checks out, you should rebuild it, soldering onto the board, and test it again.

With the camera off, discharge the two capacitors (Cl and C2) with the screwdriver. Connect the trigger wire to the OUTPUT line from the 555. Turn on the circuit, and then the camera. When the LED turns off for the first time, the camera should take a picture. (If it doesn’t take a picture, try connecting the shutter wire to the black wire.)

Mount your camera and control board to your kite, and let it fly. Then reassemble the camera and have it developed normally.

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