General Overview

The project consists of utilizing an iPod (or other stereo audio source) to control the flashing intensity of LED modules. The use of amplifiers and active high and low-pass filters allow the LED modules to flash along with the music. The circuit allows the user to connect their player to the circuit while listening to the music through amplified speakers or headphones plugged into the speaker jack. The circuit contains control potentiometers to allow the user to adjust the flash threshold to coincide with the music to which you are listening.

Tools needed: Soldering iron, solder, wire cutter & stripper, hook-up wire, utility knife, electrical tape, needle-nose pliers, mini slotted screwdriver, and a voltmeter.
Optional tools: Solder braid, fine point marker, ruler, and heat shrink tubing.
Time required: 1-3 Hours

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Order complete parts list for Pulse Project

Set up the power supply. It will supply juice to the whole system, so no cutting corners.

Cable preparation. This is what splits your audio feed into separate signals, one for headphones/speakers and one for lights.

Board assembly. All the cool components line up here. And you get to solder.

Light it up! A quick systems check and you’re ready to rock and radiate.

Tools Required tools: soldering iron, solder, wire cutter & stripper, hook-up wire, utility knife, electrical tape, needle-nose pliers, mini slotted screwdriver, voltmeter Optional tools: solder braid, fine point marker, ruler, heat shrink tubing, QC terminals, crimper, and Command™ adhesive strips

Schematic Click to enlarge

Parts List

*Note parts sold in minimum multiples of 5

Step 1: Prep the wall transformer, stereo audio cable, terminal blocks, the LED module strings, and the proto board

Cut the connector off of the wall transformer, strip off 1/4" of the insulation and tin the wires.

Cut the stereo audio cable in half, strip off 1" of the outer insulation from both halves, strip 1/4" of the insulation from each wire, twist the like wires together and tin.

Remove the alignment pins from the 6 terminal blocks with a utility knife.

Strip 1/4" off of each wire on the LED modules and tin.

Mark the top side of the proto board with the interleaved PCB bus pattern to aid in assembly. (optional)

Click on photos to enlarge.

Step 2: Place and solder terminal blocks and IC sockets on board

Position the proto board with the rectangular un-bussed section to the right.  Place and solder the 2 position transformer input connector (X1) horizontally at hole coordinates 55, 37 & 56, 37 with the terminal openings towards the top of the board. 

Place and solder the four 2 position output connectors (X2-X5) vertically at hole coordinates 55, 7 & 55, 8 : 55, 13 & 55, 14 : 55, 19 & 55, 20 : 55, 25 & 55, 26.  Place and solder the 3 position audio cable connector (X6) horizontally at hole coordinates 5, 23 & 6, 23 & 7, 23 with the terminal openings towards the bottom of the board.

Place and solder one of the 8 pin IC sockets with pin #1 at hole coordinates 40, 3 making sure that the socket straddles the bus.  Place and solder 3 additional IC sockets vertically aligned above the first on alternating busses, making sure that the sockets straddle the bus beneath them.  These IC sockets are for the LM386s (IC8, IC9, IC10, IC11).

Place and solder another 8 pin IC socket with pin #1 at hole coordinates 20, 3 making sure that the socket straddles the bus.  Place and solder 3 additional IC sockets vertically aligned above the first on alternating busses, again making sure that the sockets straddle the bus beneath them.  These IC sockets are for the TL2201s (IC2, IC3, IC4, IC5).

Click on photos to enlarge.

Step 3: Place and solder 12 volt power supply components, solder bridge IC sockets and terminal blocks to busses

On the board, label the transformer input connector as X1, and label pin #1 (X1-1) as positive, and label pin #2 (X1-2) as negative.  Label the four output connectors from the top down as X2, X3, X4, X5, and label their pins such that pin #1 is negative and pin #2 is positive.  Label the stereo audio input connector X6.

Place and solder the LM2940 (IC1) laterally into the fourth hole below the power input connector X1 pins, lining up pin #1 with the left side of the connector.  Place and solder the 220 uF input filter capacitor (C1) diagonally below the voltage regulator such that its positive and negative terminals align with pins #1 and #2 of the regulator.  

Solder bridge the negative pin of X1 to the interleaved bus above it, as well as bridging it down to pin 2 of the regulator and the negative terminal of the 220 uF filter capacitor C1.  This will provide the ground bus for the circuit.

Solder bridge the positive pin of X1 to pin 1 of the regulator and the positive terminal of C1.  Continue bridging down to the positive terminals of X2, X3, X4, and X5, making sure to run this bridge on the outside of the connectors (column 56).  This will allow for connection to the negative terminals further into the assembly process.  These positive output terminals are directly connected to the 18 volt input from the wall transformer.

Place and solder a jumper wire from pin #3 of the regulator to the other interleaved bus (56, 35 & 49, 35).  Solder bridge the wire to terminal #3 of the regulator.  This will provide the 12 volt supply bus for the circuit.  Place and solder the 100 uF filter cap (C2) across the two interleaved busses with the positive terminal at 49, 34, and the negative terminal at 51, 34.

Solder bridge the appropriate IC socket pins to the positive and negative busses.  The 4 IC sockets on the right require a positive connection at pin #6.  These 4 IC sockets require a ground connection at pins #4 and #2.

It should be noted that the lowermost socket will require a jumper wire from pin #2 to #4, and a jumper wire up to the ground bus.

The 4 IC sockets on the left require a positive connection at pin #7.  These 4 sockets require a ground connection at pin #4.  Again, it should be noted that the lowermost socket will require a jumper wire from pin 4 up to the ground bus. 

Check the solder bridge paths, busses, and IC socket pins for continuity and/or short circuits.  Connect the wall transformer, apply power, and check the 18 volt supply, the 12 volt supply, and for the correct voltage and ground on the IC socket pins.  Disconnect the wall transformer. Note: positive wire has white lines.

Click on photos to enlarge.

Step 4: Output amplifier assembly

Place and solder a 10 uF capacitor (C17, C20, C23, C26) two holes to the left of the IC sockets so that the terminals are in line with pins #1 and #8, making sure that the positive terminal is toward pin #1.  Solder bridge the capacitor terminals to the socket pins.

Bend the four 0.047 uF capacitors to a 0.6" spacing (C19, C22, C25, C28).  Place and solder the capacitors laterally with one end connecting to pin #5 on the socket and the other end out towards the left.  Bend the four 10 ohm resistors (R13, R14, R15, R16) 180 degrees.  Place and solder the resistors longitudinally with one end connecting to the unconnected end of the capacitors, and the other end connecting to the ground bus just above.

Place and solder the four trimmer potentiometers (VR1, VR2, VR3, VR4) laterally with terminal #1 two holes to the left of the 10 uF capacitors (C17, C20, C23, C26), staying in line with the positive lead of the capacitors.  Solder bridge terminal #1 of the top 3 potentiometers to the ground bus just below it.  The terminal bottom potentiometer requires the use of a jumper wire to make a connection to the ground bus above it.  Connect terminal #2 of the potentiometers to pin #3 of the IC sockets with a jumper wire.

Laterally place and solder the four ZTX869 transistors (Q1, Q2, Q3, Q4) two holes to the right of pin #4 of the IC sockets and one hole down with the emitter to the left (flat face toward bottom of board).  Solder bridge the emitter of the top 3 transistors to the ground bus below them.  Solder bridge the emitter of the bottom transistor over to pin #4 on the IC socket. 

Place and solder four 220 uF capacitors (C18, C21, C24, C27) so that the positive terminal connects to pin #5 of the IC sockets, and the negative terminal vertically lines up with the base (middle leg) of the transistors.  Place and solder a jumper wire from the negative terminal of these 4 capacitors to the base of the 4 transistors. 

Place and solder a jumper wire from the collector of the 4 transistors to the hole just to the left of the negative terminal of the four output connectors (Q1 to X2, Q2 to X3, Q3 to X4, Q4 to X5).  Solder bridge the connector negative terminals to their respective jumper wire from the transistor collectors. 

Insert the four LM386s (IC8, IC9, IC10, IC11) into the IC sockets.  This completes the assembly of the output amplifier section.

Click on photos to enlarge.

Step 5: High-pass filter assembly

Bend the legs on two of the 220 uF capacitors (C11, C14) to 90 degrees in opposite directions.  Place and solder the capacitors from pin #6 on the 2nd and 4th IC sockets from the bottom to terminal #3 of the trimmer potentiometers (VR3, VR1).  The positive terminal of the capacitors connects to pin #6 on the IC sockets.  Make sure that the positive leads are not touching pin #5 on the sockets.

Place and solder the 121K ohm resistors (R2, R4) laterally from pin #3 on the sockets with the other end four holes to the right. 

Place and solder the two TLE2426s (IC6, IC7) laterally toward the left (flat face toward top of board) with leg #1 connected to the unconnected end of the 121K ohm resistors.  Solder bridge the middle leg to the ground bus below it, and solder bridge leg #3 to the 12 volt bus above it. 

Bend the 60.4 ohm resistors (R1, R3) to 180 degrees.  Place and solder them laterally with one end connecting to pin #2 of the IC sockets and the other end 3 holes to the left.  Place and solder a jumper wire across the two IC sockets connecting pin #2 and pin #6. 

Place and solder 0.47 uF capacitors (C4, C6) from pin #3 of the IC sockets to the unconnected end of the 60.4 ohm resistors (R1, R3).  The positive terminals of the capacitors connect to pin #3 of the IC sockets.  Laterally place and solder 0.47 uF capacitors (C3, C5) with the positive terminal connecting to the junction of C4-R1 and C6-R3, with the negative terminal two holes to the left. 

Insert a TL2201 (IC2, IC4) into each of the IC sockets.  This completes the assembly of the high-pass filters. 

Click on photos to enlarge.

Step 6: Low-pass filter assembly

Bend the legs on two of the 220 uF capacitors (C13, C16) to 90 degrees in opposite directions.  Place and solder the capacitors from pin #6 on the 1st and 3rd IC sockets from the bottom to terminal #3 of the trimmer potentiometers (VR4, VR2).  The positive terminal of the capacitors connects to pin #6 on the IC sockets.  Make sure that the positive leads are not touching pin #5 on the sockets. 

Place and solder a jumper wire from pin #6 to pin #2 on the IC sockets. 

Place and solder the two of the 1.13K ohm resistors (R8, R12) laterally from pin #3 on the sockets with the other end four holes to the left.  It’s a tight fit due to the jumper wire, but be sure to use the holes closest to the IC sockets in order to leave access to the remaining open hole on pin #2. 

Place and solder the 1.0 uF capacitors (C9, C10) from pin #3 to pin #4 on the IC sockets.  The positive capacitor terminal connects to pin #3.  The capacitors will be off the board a bit due to the close proximity of the resistors. 

Laterally place and solder the 2.2 uF capacitors (C7, C8) from pin #2 of the sockets to the unconnected end of the 1.13K resistors R8 and R12.  The negative capacitor terminal connects to socket pin #2.  Again, these capacitors will be up off the board due to the close proximity of the resistors. 

Laterally place and solder the 1.13K resistors (R7, R11) right next to, and to the left of the 2.2 uF capacitors C7 and C8 (0.4" spacing).  Solder bridge the adjacent ends of the resistors and capacitors, R7 to C7, and R11 to C8. 

Bend two of the 100K ohm resistors (R5, R9) to 180 degrees.  Vertically place and solder them with one end connecting to the unconnected end of resistors R7 and R11, with the other end to the 12 volt bus just above them. 

Vertically place and solder the remaining two 100K ohm resistors (R6, R10) with one end from the junction of resistors R7-R5 and the junction of resistors R11-R9, and the other end to the ground bus located above them.  Placement of the resistor bodies should be to the right of R5 and R9. 

Laterally place and solder the remaining 220 uF capacitors (C12, C15) inline and adjacent to the left of R7 and R11, with the negative terminal of the capacitors towards the resistors.  Solder bridge the negative terminal of C12 to R7 and C15 to R11. 

Insert a TL2201 (IC3, IC5) into each of the IC sockets.  This completes the assembly of the low-pass filters.

Click on photos to enlarge.

Step 7: Stereo input connector assembly

Solder bridge the middle terminal of the three position terminal block (X6) to the ground bus located below it. 

Place a jumper wire from the negative terminal of capacitor C3 (0.47 uF) to the positive terminal of capacitor C12 (220 uF). 

Place a jumper wire from the negative terminal of capacitor C5 (0.47 uF) to the positive terminal of capacitor C15 (220 uF). 

Place a jumper wire from the negative terminal of capacitor C3 (0.47 uF) to the open hole just to the left of terminal block X6.  Solder bridge the jumper wire to terminal #1 of X6. 

Place a jumper wire from the negative terminal of capacitor C5 (0.47 uF) to the open hole just to the right of terminal block X6.  Solder bridge the jumper wire to terminal #3 of X6.  This completes the board assembly.

Click on photos to enlarge.

Step 8: LED module string assembly

The LED module string assembly is pretty straightforward.  Select the module color sequence you want for each of the four outputs:  left high-pass, left low-pass, right high-pass, and right low-pass.  Solder the leads on each module to each other, gray to gray, white to white, and wrap the connections with electrical tape to prevent shorting.  The wire leads on the end module of each string should also be taped or have no bare wire showing to prevent shorting.

It should be noted that the overall current draw from all four of the LED module strings combined should not exceed 800 milliamps.  For reference, the red and yellow modules draw approximately 45 milliamps each, while the green, white, and blue modules draw approximately 25 milliamps.

Click on photos to enlarge.

Step 9: Final connections and adjustment

Connect the four LED module strings to terminal blocks X2, X3, X4, and X5, with the gray wire to the positive terminal of the connectors and the white wire to the negative terminal. 

Connect the stereo audio cable to terminal block X6 with the white wire to terminal #1, ground shield to terminal #2, and the red wire to terminal #3. 

Connect the wall transformer to terminal block X1 with ground to terminal #1 and positive (wire with white lines) to terminal #2. 

Turn the four trimmer potentiometers VR1, VR2, VR3, and VR4 to approximately mid-range. 

Plug in the wall transformer.  The four LED strings should light for a few seconds until the output capacitors charge, and then go out.  Unplug the wall transformer. 

Plug the male end of the stereo cable into your audio source (iPOD, etc.).  Plug your amplified speakers into the female connector of the stereo cable.

NOTE:  Due to the input volume level required to obtain the best circuit response, it is not recommended that headphones be plugged directly into the female connector.  Instead, use the headphone jack on the amplified speakers to allow for volume adjustment. 

Plug in the wall transformer and power up the speakers and your audio source.  Adjust the volume on your audio source until the LED strings show a decent response to the highs and lows of the music.  Use the trimmer potentiometers to fine tune the response of the LED strings.  Turning them clockwise will increase the LED string response.

Click on photos to enlarge.