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"I See Dead Pumpkins"
By Design News Staff -- Design News, October 10, 2004
There's no better Halloween prop than a carved pumpkin. But Mark didn't like the idea of leaving burning candles unattended in his squash, so he built a battery-powered light source instead. For a realistic effect, he used a timer circuit that produces a pseudo-random timer pattern that makes two ultra-bright orange LEDs flicker, simulating a flame. The power source is four batteries at 1.5V or two 9V batteries wired in parallel for more current and longer glowing time.
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| "Scary Pumpkin" Parts List | ||
|---|---|---|
| Amt | Part Description | Allied Part # |
| 1 | Quad 2 input NAND Schmitt MC 14093BCP | 568-3021 |
| 1 | LM7805 voltage regulator +5V dc | 288-0001 |
| 4 | 1N4148 diode | 263-1538 |
| 2 | Orange ultra bright 5 mm LED | 505-9712 |
| 4 | 2N2222 transistors NPN | 248-1004 |
| 1 | Switch on-off | 855-1099 |
| 1 | Enclosure plastic 3 × 2.5 × 1.5 | 736-7404 |
| 4 | Capacitor ceramic 104, 0.1 F | 881-3486 |
| 1 | Capacitor electrolytic 100F | 852-7029 |
| 4 | Trimmer Potentiometers | 754-2719 |
| Additional parts required: 18-2 stranded power wire (5 ft), 9V battery and straps, plastic drywall anchor screw, assorted resistors | ||
For Mark McCuller's instructions on how to create your own "scary pumpkin," click here.
To view a schematic drawing of McCuller's "scary pumpkin," click here.
Talkback
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Mark's LED ON state is the AND of two squarewaves. Driving the LED with two PNP's would yield...
- 2006-17-10 15:09:52 EDT -
Using two NPN transistors to drive each LED results in current being drawn from the battery all...
- 2006-15-10 08:24:39 EDT
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