电子产品世界

舞蹈发光二极管电路--Dancing LEDs

Parts:

R1_____________10K 1/4W ResistorR2,R3__________47K 1/4W ResistorsR4______________1K 1/4W ResistorR5,R6,R7______100K 1/4W ResistorsR8____________820R 1/4W ResistorC1,C3_________100nF 63V Ceramic or Polyester CapacitorsC2_____________10F 50V Electrolytic CapacitorC4____________330nF 63V Polyester Capacitor (See Notes)C5____________100F 25V Electrolytic CapacitorD1___________1N4148 75V 150mA DiodeD2-D11_________5 or 3mm. LEDs (any type and color)IC1___________LM358 Low Power Dual Op-ampIC2____________4017 Decade counter with 10 decoded outputs ICM1_____________Miniature electret microphoneSW1____________SPST miniature Slider SwitchB1_______________9V PP3 BatteryClip for PP3 Battery

Additional circuit parts (see Notes):

R9,R10_________10K 1/4W ResistorsR11____________56R 1/4W ResistorD12,D13 etc.____5 or 3mm. LEDs (any type and color)Q1,Q2_________BC327 45V 800mA PNP TransistorsQ3____________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 lastVisited="0">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, lastVisited="0">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.