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Two Rhythmic LED as Flashing Eyes for Halloween

2014-12-17 04:42  
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Figure 1 

Part List
The circuit was designed to be used as flashing eyes in Halloween gadgets with the addition of rhythmic music or speech while being powered by 3 V battery.

BC547 –NPNsmall signal transistors designed for general purpose switching and amplification due to its low voltage, low current and three different gain selectionsBC557 –PNPgeneral purpose transistors used for amplification and switching due to its low current and low voltage

Along with the twoLEDs is a miniature electret microphone that picks-up any form of speech in the surroundings. The electret microphone is a type of condenser of capacitor microphone that utilizes a permanently charged object to eliminate the use of a power supply. The two transistors Q1 & Q2 will provide the necessary amplification of the received signals and then drive theLEDs to do flashing effects by illuminating more or less brightly with matching rhythm of the music.

The type of transistors used for Q1 & Q2 can be of any general purpose and small signal but could require the adjustment of resistor R3. The adjustment will depend on the gain of Q1. The suggested resistor value on the diagram will remain the same if medium gain transistor is used while for high gain transistors, a lower value of R3 is required which ranges from 390 Ohms to 470 Ohms. In order to set the threshold of the circuit in a précised value, a 1K Ohm trimmer can replace R3 for easy regulation of the value.

High efficiencyLEDcan produce a better effect from its illumination but any type ofLEDand color can still be used for as long as the size conforms to 2mm in diameter. TheLEDs D1 & D2 will not require limiting resistors which would limit the flow of the current to some predetermined value. They can be optionally added for protection of components during warm-up.

An approximate 1.5 mA current is being drawn during standby. The batteries to be used will depend on the dimensions of the equipment to where this circuit will be used. There should be two 1.5 V batteries for AA,AAA,AAAAtypes for photo camera type of equipment and button dock type. Two pieces of1.4 V for mercury batteries and one piece for 3 V for Lithium type cells.

The Halloween flashing eyes circuit is suitable for badges or pins that contain Halloween characters and images like the pumpkin, black cat, Halloween mask corpse, skull, skeleton, hanging ghost, musical climbing Halloween witch, in misty bowls, and Halloween bat. It can also be used with gauze zombie costumes with flashing eyes inside an invisible mask with attached hood, and light-up fading eyes.


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