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How to build Dancing LEDs
November 11, 2010 - category: Light flasherA LED sequencer, following the rhythm of music or speech
9V Battery-operated portable unit
Circuit diagram
Parts:
- R1 10K 1/4W Resistor
- R2,R3 47K 1/4W Resistors
- R4 1K 1/4W Resistor
- R5,R6,R7 100K 1/4W Resistors
- R8 820R 1/4W Resistor
- C1,C3 100nF 63V Ceramic or Polyester Capacitors
- C2 10µF 50V Electrolytic Capacitor
- C4 330nF 63V Polyester Capacitor (See Notes)
- C5 100µF 25V Electrolytic Capacitor
- D1 1N4148 75V 150mA Diode
- D2-D11 5 or 3mm. LEDs (any type and color)
- IC1 LM358 Low Power Dual Op-amp
- IC2 4017 Decade counter with 10 decoded outputs IC
- M1 Miniature electret microphone
- SW1 SPST miniature Slider Switch
- B1 9V PP3 Battery
- Clip for PP3 Battery
- Additional circuit parts (see Notes):
- R9,R10 10K 1/4W Resistors
- R11 56R 1/4W Resistor
- D12,D13 etc 5 or 3mm. LEDs (any type and color)
- Q1,Q2 BC327 45V 800mA PNP Transistors
- Q3 BC337 45V 800mA NPN Transistor
Device purpose:
The basic circuit illuminates up to ten LEDs in sequence, following the rhythm of music or speech picked-up by a small microphone. The expanded version can drive up to ten strips, formed by up to five LEDs each, at 9V supply.
Circuit operation:
IC1A amplifies about 100 times the audio signal picked-up by the microphone and drives IC1B acting as peak-voltage detector. Its output peaks are synchronous with the peaks of the input signal and clock IC2, a ring decade counter capable of driving up to ten LEDs in sequence. An additional circuit allows the driving of up to ten strips, made up by five LEDs each (max.), at 9V supply. It is formed by a 10mA constant current source (Q1 & Q2) common to all LED strips and by a switching transistor (Q3), driving a strip obtained from 2 to 5 series-connected LEDs. Therefore one transistor and its Base resistor are required to drive each strip used.
Notes:
- The sensitivity of the circuit can be varied changing R4 value.
- C4 value can be varied from 220 to 470nF in order to change the circuit speed-response to music peaks.
- Adopting the additional circuit, only one item for R10, R11, Q1 and Q2 is required to drive up to ten LED strips. On the contrary, one item of R9 and Q3 is necessary to drive each strip you decided to use.
- Each R9 input must be connected to IC2 output pins, in place of the LEDs D2-D11 shown. R8 must also be omitted.
- Whishing to use a lower number of LEDs or LED strips, pin #15 of IC2 must be disconnected from ground and connected to the first unused output pin. Example:
- if you decided to use 5 LEDs, pin #15 of IC2 must be connected to pin #1; if you decided to use 8 LEDs, pin #15 of IC2 must be connected to pin #9 etc.
- Current drawing of the circuit is about 10mA.
- Whishing to use a wall-plug transformer-supply instead of a 9V battery, you can supply the circuit at 12V, allowing the use of up to 6 LEDs per strip, or at 15V, allowing the use of up to 7 LEDs per strip.
author: RED Free Circuit Designs
circuit from http://www.redcircuits.com/
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