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Light up your music with the . . . LE D MUSICOL OUR Pt.2: By NICHOLAS VINEN The new LED Musicolour makes building a spectacular light and music show easier than ever. In this second and final instalment, we explain how to build and test the unit and also detail how you can control it. W E’LL GET onto the construction of the LED Musicolour shortly. Before we do, let’s quickly look at a few more design details. One aspect of the unit’s operation that we didn’t mention in Pt.1 is the automatic gain control (AGC). This applies when you are feeding audio into the unit via the audio line input socket (CON11). The problem is that line level signal amplitude can be quite 38  Silicon Chip variable and we don’t want the lights to be driven dimly simply because your signal source has a low peak voltage. To solve this, we constantly monitor the peak voltage at the audio inputs and apply an asymmetrical low-pass (smoothing) function to it. The output of this function remains close to the long-term peak of the audio signal, even though the amplitude won’t be constant. We do this by allowing the detected peak voltage value to increase rapidly but only decrease slowly. Given this detected peak amplitude, we can then “normalise” the audio data by computing a gain value which is the inverse of this peak amplitude, ie, the lower the amplitude, the higher the gain. This gain is applied before the Fast Fourier Transform (FFT) function is applied to the audio data. The output of the FFT then gives a consistent brightness level over a range of input signal amplitudes from around 500mV RMS up to a little over 2V RMS. When we describe the configuration options later, you will see that there are a few options which control the rate at which the AGC level changes and the maximum gain setting available. We’ve chosen defaults that work well siliconchip.com.au siliconchip.com.au No.   2   2   3   3   5   1   6   2   1 19   1 Value 1MΩ 120kΩ 100kΩ 47kΩ 10kΩ 4.7kΩ 1kΩ 470Ω 220Ω 100Ω 10Ω T 1k 4004 100 100 100 100 4.7k 47k 100 10F 100nF 100nF 10 220 IC2 WM8759 S 1k 1M 100 100pF 10k + CON12 OUTPUT LM3940IT-3.3 Q10 BC327 100F + 100 1M + R LED1 47k A IRD1 Fig.3: install the parts on the PCB as shown in this diagram, starting with the SMD components. The off-board LED strips are connected to pin headers CON1CON8 via matching header sockets. Note that infrared receiver IRD1 is installed upside down (see text and photo). bridges between the pins. If there are, use solder wick to clean them up. That’s best done by first adding a little liquid flux paste (no-clean type) along both rows of pins and then removing any excess solder using the solder wick. You can clean up the flux residue with isopropyl alcohol if you like. Note that for each of Q1-Q8, two pairs of pins share a single, larger pad. These are the two Mosfet drains. Obviously you don’t have to worry Table 1: Resistor Colour Codes o o o o o o o o o o o o CON13 SD CARD SOCKET 100nF 12101161 + + S 220F 10F C 2012 ruolocisuM DEL 10F 100F 100F LED Musicolour REG2 10F + + 100nF 10F 100nF + BAT85 220F 33pF IC1 dsPIC33FJ128GP802 47k BAT85 T 10nF 8MHz C + BAT85 CON11 INPUT 10nF 100nF BAT85 100pF R 1k 10k D2–D5 X1 100F 2102 100F Building the main PCB is relatively straightforward and should take just a few hours. Fig.3 shows the parts layout. The board is coded 16110121 and measures 103 x 118mm. The 11 SMD components are mount­ ed first, ie, the eight dual Mosfets (Q1-Q8), audio DAC IC2, the 10µF ceramic capacitor for IC1 and the SD card socket (CON13). Start with Mosfets Q1-Q8, which are in 8-pin SOIC packages. In each case, the pin 1 dot goes towards the lefthand side of the PCB. Place a small amount of solder on one pad, line up the IC and slide it into place while heating that solder. If it isn’t positioned correctly on its pads, reheat the solder and reposition it. Make sure it’s sitting flat on the board, then solder the remaining pins. Finally, add some more solder to the first pin. That done, check that there are no 100 100 470 33pF 100nF Construction 100 100 IC3 74HC393 10k 100k 120k 10k 120k 100k 100nF 100nF IC5 74HC595 470 D1 LOW ESR 220F 25V + IC4 LM358 100nF 1k 100nF F1: 10A + 1k 100nF Q1 REG1 7805 10k CON10 CON9 CON1 Q2 Q3 16110121 IC6 74HC595 CON2 + BC547 Q9 CON3 + 100nF CON4 Q4 Q5 100 100 100 100 CON5 Q6 Q7 100 1k 100k 100 Q8 Throughout these articles we have generally referred to the memory card as an “SD card”. There are actually several different types of SD card. These days, most cards sold are actually SDHC (high capacity) cards in the range of about 4GB-32GB. We have successfully tested the largest of these cards in the LED Musicolour. It should also support the older MMC cards although they are basically obsolete now. We haven’t tested SDXC (64GB+) cards but in theory, they should work too as they still support the 1-wire SPI interface we are using to communicate with the memory card. CON6 CON7 100 CON8 100 Memory cards + in most circumstances so you won’t normally need to change these. 4-Band Code (1%) brown black green brown brown red yellow brown brown black yellow brown yellow violet orange brown brown black orange brown yellow violet red brown brown black red brown yellow violet brown brown red red brown brown brown black brown brown brown black black brown about these being bridged although you should check that the two drains are not accidentally shorted. Fit the rest of the SMD parts using the same method, with the exception Table 2: Capacitor Codes Value µF Value IEC Code EIA Code 100nF 0.1µF 100n 104 10nF 0.01µF   10n 103 100pF NA 100p 101 33pF NA   33p   33 5-Band Code (1%) brown black black yellow brown brown red black orange brown brown black black orange brown yellow violet black red brown brown black black red brown yellow violet black brown brown brown black black brown brown yellow violet black black brown red red black black brown brown black black black brown brown black black gold brown November 2012  39 The fully-assembled PCB is shown above, while the photo at right shows how it fits inside the specified plastic case. Note the small heatsink fitted to regulator REG1. These two photos show the mounting details for the infrared receiver (IRD1). It must be mounted upside down (so that its lens lines up with the adjacent LED), with its leads run down the back of its body. of the SD card holder. This has two plastic posts which go into holes on the PCB, holding it in position. You then solder the larger mounting tabs, followed by the signal pins. There are 15 in all; remove and discard the plastic insert before soldering those inside the socket. Through-hole parts Now mount the resistors, checking each value with a DMM first. You can refer to the colour code table but the multimeter is more reliable. Follow with diode D1 (1N4004) and then the four smaller Schottky diodes, D2-D5. In each case, ensure that the cathode stripe is orientated as shown. 40  Silicon Chip Solder crystal X1 in place next, then fit the IC sockets or, if you are not using a socket at any location, the IC itself. It’s a good idea to use a socket for IC1 but the rest are optional. Either way, make sure the pin 1 notches are all orientated towards the righthand side of the PCB, as shown on the overlay. Next, bend REG2’s leads down through 90° about 7mm from its tab, then use an M3 x 6mm machine screw, shakeproof washer and nut to fasten it to the board. Do the screw up tight, then solder and trim the leads. That done, install the two 3.5mm stereo jack sockets. These must sit flush against the PCB and must be correctly aligned with its edge. Follow with the two small signal transistors, taking care not to get them mixed up. Bend their leads with small pliers to suit the pad spacing on the board. Pin headers CON1-CON8 can now go in. If you can’t get 8-pin dual row right-angle pin headers, make them from longer, snappable headers. Do this carefully using pliers and file off any burrs. Check that each header fits through the hole in the rear panel before soldering it to the PCB. When doing so, take care that the projecting pins are parallel to the surface of the PCB and at right-angles to the edge. If one of the headers won’t fit through the rear panel, a few strokes with a needle file will generally take off enough plastic to fix it. This is easier to do before the header is soldered to the board. It’s also a good idea to check the alignment of each header once you have soldered a couple of its pins. With the pin headers in place, you can then mount CON9 and CON10, again checking that they are aligned correctly to fit through the rear panel hole. Follow with the two fuse clips; push them down all the way onto the PCB and check that the end-stops are on the outside. The MKT and ceramic capacitors go in next, in the locations shown on the overlay diagram. Follow with the siliconchip.com.au the screw firmly before soldering and trimming REG1’s leads. The PCB assembly can now be completed by fitting the 10A fuse and plugging the ICs into their sockets. Make sure that the pin 1 notch or dot of each IC goes towards the righthand side of the PCB – see Fig.3. Putting it in the case Before fitting the PCB into the case, first you must cut off or file down the four inner plastic posts in the base, ie, the ones which don’t correspond with the PCB corner mounting holes. That done, push the rear panel onto the PCB connectors until it sits against the edge of the board. It should be a tight fit. If it won’t go, carefully use a needle file to slightly enlarge the offending cut-out and try again. With the rear panel in place, you can then unscrew the nuts for the two 3.5mm stereo sockets and slip the front panel on. It should fit easily but again, if it doesn’t, a little filing should fix it. Check that LED1 and infrared receiver IRD1 are properly aligned with their holes and if not, adjust them. Once the panel is in place, refit the two nuts to the sockets to hold it in place. You can now slip the whole assembly down into the channels in the bottom of the case and attach the board to the integral stand-offs using four self-tapping screws. electrolytic capacitors, ensuring that in each case, the longer lead goes into the hole marked with a “+” on the overlay diagram. That done, bend the green LED’s leads down 2mm from its lens so that when fitted, its anode (longer lead) will go towards the right. Solder it in place with the horizontal portion of the leads 3mm above the PCB. Don’t trim the leads too short in case you need to adjust it later. Infrared receiver IRD1 is installed in an unusual manner – basically upside-down, so that the centre of its lens is aligned with the other front panel connectors and the LED. This means the leads run down the back of the receiver and the top of the housing sits on the surface of the PCB. We used a plastic-encapsulated type but some infrared receivers have a metal shield. Because the leads run near the body of the device and besiliconchip.com.au cause of the exposed pads on the PCB, you will have to place an insulating layer (eg, electrical tape) over the back and top side of the receiver. There’s a bit of a trap here because you might expect that this is unnecessary for IR receivers which have a plastic case. In fact, many of these use a conductive type of plastic (for shielding) so you should put some insulation along the rear and top of these as well. Make sure the body can’t make contact with the leads or PCB pads. If it does, the receiver won’t work. Once you’re ready, bend the leads through 180°, against the insulation layer on the rear of the receiver, then push it down all the way onto the PCB and solder it in place. The accompanying photos show how we did it. Now bend regulator REG1’s leads down through 90° in a similar manner as for REG2. This device is then fastened to the PCB along with a mini-U heatsink using an M3 x 10mm machine screw nut and flat washer. Tighten Testing It’s best to test the unit initially without the LED strips plugged in. You can use a 7.5-24V DC plugpack if you have one handy. Alternatively, use the 12-24V power supply you will be using later. Plug in the supply and switch on. Check that LED1 lights immediately. If it doesn’t, switch off and check for faults (make sure IC1 has been programmed correctly). If all is well, measure the outputs of REG1 and REG2. Connect the negative lead of a DMM to the tab of either regulator and then, with the board orientated as in Fig.3, measure the voltage on the top pin of REG1 and the lefthand pin of REG2. You should get readings in the range of 4.8-5.2V for REG1 and 3.2-3.4V for REG2. If you plan to use an infrared remote control, you can point a universal remote set for a common Philips device code (TV, VCR, etc) and press some buttons. The green LED should flash November 2012  41 Table 1 – Infrared Remote Control Commands Button Command Description Play Stop Pause Down arrow Up arrow Right arrow play stop pause next_folder prev_folder next_file Left arrow prev_file Channel + Channel Volume + Volume Mute Fast forward Rewind 0-9 Power Record next_mode prev_mode volup voldn mute forward back 0-9 reset order Starts or resumes playback Stops playback. Pressing it twice resets the unit. Pauses or resumes playback Play first file in next folder Play first file in previous folder Play next file in this folder (will skip to next folder on last file) Play last file in this folder (will skip to previous folder on first file) Changes light display mode; see Table 2 Changes light display mode; see Table 2 Increases volume in ~1dB steps (default is 0dB) Decreases volume in ~1dB steps (minimum is about -30dB) Toggles mute mode Skip ahead 10 seconds Skip back 10 seconds Goes to a specific light display mode; see Table 2 Resets device to initial settings Cycles file order through sorted shuffle and directory (see text) Table 2 – Light Display Modes Mode 0 1 2 3 4 5 6 7 8 9 Description 16 frequency bands, 40Hz-4kHz, combining both channels (default) Two sets of 8 frequency bands, 40Hz-4kHz, one for each channel 16 frequency bands, 40-750Hz, combining both channels 16 frequency bands, 750Hz-4kHz, combining both channels 16 frequency bands, 40Hz-4kHz, left channel only 16 frequency bands, 40Hz-4kHz, right channel only 16 frequency bands, 40-750Hz, left channel only 16 frequency bands, 750Hz-4kHz, left channel only 16 frequency bands, 40-750Hz, right channel only 16 frequency bands, 750Hz-4kHz, right channel only in response. If not, try a different code and failing that, check that the left and right pins on the infrared receiver are not shorted to ground (possibly via the case). In the quiescent state, these pins should both measure at least 3V. If you have an SD card, copy a 44.1kHz or 48kHz 16-bit stereo WAV file to its root folder and plug it in. The green LED should flash a few times and if you now connect the LED Musicolour’s line output to a stereo amplifier, you should hear the audio file being played back. Remove the SD card when you have finished. You can also test the audio input. It’s simply a matter of connecting it to a signal source such as a DVD player, MP3 player or computer sound card and again feeding the output into a stereo amplifier. 42  Silicon Chip Finally, with no SD card inserted and nothing plugged into the audio input or output jacks, plug in one or more LED strips (it’s OK to do this while the unit is running). Within 30s of switching on, the unit should go into a test mode where the LED strips fade up and down in brightness, in a pattern moving from output 1 through to output 16 and then repeating. You can use this test mode to verify that all the LED outputs are working properly and that you have the strips connected in the right sequence. When you do, the light should appear to move smoothly from one side of the display to the other. If it all checks out, you can put the lid on the case. If any of the tests fail, switch off and check the PCB carefully for faults. Inspect the SMD and through-hole solder joints and verify that the correct components are installed in each location. Check also that all polarised components (diodes, electrolytic capacitors, ICs) are the right way around. Wiring the LED strips You may be able to purchase LED strips with 4-pin female connectors already attached but many strips come with bare wires or just pads on the end of the flexible PCB. In this case you will need to connect a length of 2-way or 4-way cable with a pin header at the end. The easiest way is to buy pre-made cables with 4-pin female headers at each end and chop them in half. These are available from various online retailers such as Australian Robotics (http://australianrobotics.com.au – SKU PRT-10364) or Seeed (www. seeedstudio.com – SKU CAB104C4O). It is possible to crimp your own connectors but this is a fiddly task without a specialised crimping tool. The plugs are available from element14 (eg, Cat. 865620 & 1022220) and Futurlec (HDCONNS4 & HDPINF). Using it At this stage, you can plug everything in, turn it on, sit back and watch. However, you may want to do some additional configuration or learn how to use the remote control commands. If you are going to use a universal infrared remote, the Jaycar AR1726 should be set to TV code 102 and the AR1723 to code 0348. The Altronics A1012 should be set to TV code 156. Other universal remotes should work but you may have to try multiple Philips TV codes before you find the right one. Refer to Table 1 to see which button does what. Note that the IR command codes can be changed – see below. Play, stop, pause, mute, fast forward/rewind and volume up/down are all self-explanatory. If you only want to play a few audio files, you can place them all in the SD card’s root folder or a sub-folder and then simply use the left and right arrow buttons (next and previous file commands) to skip between them. However, given the high capacities of SD cards that are available today (64GB or more), you can put a lot of WAV files onto one card and skipping through them individually can be a siliconchip.com.au The 16-channel outputs from the unit are connected to the coloured LED strings via 4-way pin headers (two pins for the positive rail and two for the switched negative rail). chore. So you can instead organise them into separate folders. The next and previous file commands will still skip through the whole lot but you can also use the Up and Down arrows on the remote to skip to the previous or next folder respectively. That way, you can quickly locate the folder with the file(s) that you want to play back and then use the Left and Right arrows to select the desired file. Each folder can contain one CD’s worth of audio files or you can organise them however you want (by genre, by performer, etc). SILICON CHIP Normally, the order in which files and folders are played is alphabetical. You can change this to random (shuffle) or directory order (the order the file entries are stored on the card). This is done either by pressing the Record button on the remote control or with the configuration file, as explained below. Lighting modes The lighting modes available are shown in Table 2. The default is mode 0. In this mode, the audio data from the left and right channels is mixed to form a mono signal and this is then LED Musicolour Audio Input Audio Output Memory Card + + - On/Ack SILICON CHIP 12V/24V DC - split up into 16 frequency bands, more or less equally spaced over the six or so octaves from 40Hz to 4kHz. The audio energy in each band then determines the brightness of the corresponding LED strip, where LEDs1 correspond to the lowest band (~0-40Hz) and LEDs16 correspond to the highest band (~3.5-4kHz). With mode 1, the difference is that the channels are processed separately and are used to drive LEDs1-LEDs8 (left) and LEDs9-LEDs16 (right). Each band therefore covers a larger range of frequencies. Fig.4: the front & rear panel designs for the LED Musicolour. Cutting the plastic endpanels provided with the case is very difficult given the number and shape of the cut-outs so we are offering premade PCB panels with screen-printed labels (see parts list in Pt.1). 12V/24V LED Outputs 15 13 11 9 7 5 3 1 + - - + + - - + + - - + + - - + + - - + + - - + + - - + + - - + 10A siliconchip.com.au <3A + - - + + - - + + - - + + - - + + - - + + - - + + - - + + - - + 16 14 12 10 8 6 4 2 November 2012  43 Table 3 – Configuration Commands Setting Valid Options Description mode spectrum attack spectrum decay min brightness default playback order default volume start playback automatically default repeat all agc filter coefficient 0-9 0-255 0-255 0-255 sorted,shuffle,directory 0-100% yes,no,true,false yes,no,true,false 0-65535 agc max error 0-65535 agc max agc delta limit 0-65535 0-65535 remote code <command> RC5(0x????) infrared logging on,off Which light display mode the unit starts up in (default=0) If set below 255, limits the rate at which LED brightness can increase (default=255) If set below 255, limits the rate at which LED brightness can decrease (default=255) Brightness level below which a strip remains off (default=8) Which order WAV files and folders are processed (default=sorted) The initial sound output volume (default=100%) If yes/true, playback starts immediately If yes/true, when the last file is finished playing, it starts again with the first (default=yes) AGC low-pass filter coefficient, lower values give slower gain changes (default=16) Amount by which AGC output is allowed to deviate from nominal before gain changes (default=256) Maximum allowable AGC gain, multiplied by 4096 (default=16384, ie, gain of four) Maximum change in AGC gain in a single step (default=4) Changes the 16-bit RC5 code assigned to a given command; number can be decimal or hexadecimal as shown. See Table 1 for command names. If set to on, valid RC5 remote control codes detected are written to a log file on the SD card (default=off) the configuration file. For example, if you want to simulate a “peak hold” spectrum analyser, you can set the spectrum decay setting low (say, to 8). This means that a LED strip driven at full brightness will stay on for 256 ÷ 8 = 32 window periods or about 1.5 seconds. You can play around with the attack and decay settings to see if you prefer the effect achieved. As you can see from the table, there are quite a few settings although many of them are provided for people who really want to tweak the way the unit works. Most of the settings can simply be left at their defaults. This view shows how the LED strips are wired to the 4-way header sockets. The two outer leads go to the positive rail while the inner leads go to the negative rail, so the socket can be plugged into a header either way around. Modes 2-9 are similar to modes 0 and 1 but are intended for use when you have more than one LED Musicolour unit. For two units, you feed them the same audio and then use either modes 2 & 3, with each unit processing half the frequency bands, or modes 4 & 5, with each unit processing one channel. With four units, set them to modes 6-9. Of course, if you prefer the way one of these other modes looks with a single Musicolour, there’s nothing stopping you from using it that way too. Configuration file So that you don’t have to change the settings with the remote control 44  Silicon Chip each time you power the unit on, you can record them in a configuration file in the root folder of the SD card. This works even if you don’t want to use the SD card to play back audio; if you don’t put any WAV files on the card, the unit will instead utilise its audio input, just as if there was no card inserted. This file must be called “LED Musicolour.cfg” and contains one line per setting. Each line starts with the name of that setting, then has an equals sign (“=”) and then the value. The options are shown in Table 3. Any settings not specified remain at the default value. There are some options to control parameters that you can only set using SD card bootloader In case of bugs in the firmware, we have incorporated a “bootloader”. This checks for the presence of a certain HEX file in the root folder of the SD card when power is first applied. If it exists and its contents differ from the micro’s flash memory, the bootloader re-flashes the micro. During this process, LED1 flashes. From then on, the microcontroller will run using the new firmware from that HEX file. The file must be called “LED Musicolour.hex”. If we release an updated version of the firmware, it will probably have a different file name so you will need to rename it after copying it to the memory card. Once the unit has successfully been re-flashed, you should delete the file from the SD card. SC That’s it; enjoy the show! siliconchip.com.au