LED Pumpkin Candles for Colorful Halloween Jack-O-Lanterns

Posted on Feb 4, 2014

Discrete blinking LEDs are convenient, but the blink rate and blink duration are not configurable. I tried goofing around with using transistors, resistors, and capacitors to alter the blinking LED. In the end, I had so many extra electronic components that I figured it would be easier to simply program the lighting effect with software. As soon a

LED Pumpkin Candles for Colorful Halloween Jack-O-Lanterns
Click here to download the full size of the above Circuit.

s a circuit includes a microcontroller (MCU), it cuts down on the number of hobbyists that are capable of implementing it. Nevertheless, I decided to include this more complex circuit in this article to demonstrate the possibilities. A number of fancy electronics (computers, MP3 players, etc) now include a pulsing LED that fades in and out. For example, a pulsing LED may indicate that the device is sleeping (in a low power mode). The circuit has become much more complicated because the microcontroller can`t run on 9 volts. A Microchip MCP1702 LDO (low-dropout) voltage regulator (VR1) steps down the battery voltage to 5 volts for the microcontroller section. Several capacitors (C1 and C2) steady the voltage supply to avoid electrical glitches and noise. A diode (D1) protects all of the electronics components against a reversed battery. This wasn`t necessary in previous circuits because the strands of LEDs wouldn`t be harmed by a reversed battery. But now, a microcontroller and other sophisticated semiconductor parts are installed, and they can be harmed by a flipped battery. The Atmel ATTiny45 microcontroller has firmware (software inside a chip) that is written in C on a personal computer. The compiled software is then downloaded to the chip by an Atmel programmer. I use an Atmel STK500 board and the ImageCraft C compiler. In the circuit, the Atmel microcontroller reads the trimpot (R2) using the built-in Atmel ADC...

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