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Electronic Candle Blow Out (1N4148)

2017-08-03 08:10  
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This paper introduces the Electronic Candle Blow Out (1N4148). This principle is easy to understand, but also very practical. Depth understanding of circuit elements, can be more effective to grasp this principle. Do you know the circuit, for example, can understand and buy these components: BC550C , BC337, BC327, 1N4148 .

LEDor bulb switch off with a puff, Funny gadget – 3V Battery supply

This design was developed by request of a correspondent having made a sort ofLEDcandle and needing to switch off theLEDwith a puff. This simple, easy to build gadget can be useful as a prop for Halloween and Christmas season, shows and the like. Q2 & Q3 form a self-latching pair that start operating when P1 is pushed: in this way theLED(or bulb) will illuminate steadily. When someone emits a strong puff in the vicinity of the small electret microphone,

The resulting signal will be greatly amplified by Q1 and a rather long positive pulse (shaped by D1 and C2) will reset the self latching pair through the Emitter of Q2. The very low (and unusual) value of C1 acts as a simple high-pass filter, in order to prevent that normal speech or environmental noise shut off the device. Obviously, such a simple filter cannot be very discriminating, therefore, not only a strong puff will reset the circuit but also a loud shout, blow, clap or stroke.

Figure:1 Electronic Candle Blow Out Circuit Diagram

Figure 1 Electronic Candle Blow Out Circuit Diagram


R1 = 10K
R2 = 1M
R3 = 1K
R4 = 4.7K
R5 = 10K
R6 = 100R
C1 = 100pF-63V
C2 = 10μF-25V
C3 = 100nF-63V
D1 = 1N4148
D2 = RedLED
P1 =SPSTPushbutton Switch
B1 = 3V Battery (2 × 1.5V AA,AAACells in series etc.)
Q1 = BC550C-45V 100mANPNTransistor
Q2 = BC337-45V 800mANPNTransistor
Q3 = BC327-45V 800mAPNPTransistor
MIC1 = Miniature electret microphone


A small bulb can be used in place of theLED. In this case a 3 – 3.5V, 0.7W (200mA) incandescent bulb can be used satisfactorily. Therefore, D2, R5 and R6 must be omitted, the bulb wired in place of R5 and R4 value changed to 1K5.Using a bulb instead of theLED, a 1.5V battery supply could also be used. A 1.5V, 0.3A incandescent bulb will work, but R4 must be replaced by a 470 Ohm Trimmer, adjusted to allow a reliable circuit operation.Please note that the circuit will draw a small current even when theLEDor bulb are off. This current is about 1.2mA for theLEDversion of the circuit, 1.5mA for the 3V bulb version and 1mA for the 1.5V bulb version. Therefore, in some circumstances, the addition of a power on-off switch could be necessary. 


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