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Pardy Lites By Ross Tester Having a party this festive season? Here’s a light display which will really add to the occasion. It’s easy to build, safe and adaptable to a wide range of hardware. It’s not a chaser and it’s not a colour organ. So what is it? Intriguing, that’s what! I f you’re looking for something to brighten up a Christmas or New Years party – literally brighten – this project could be right up your alley. It consists of four coloured 12V, 50W halogen globes which are driven in somewhat random patterns by the bass beat from your music. And if there’s no music, it automatically switches over to its own random display. You don’t need to make any connection to your amplifier or speakers: an inbuilt microphone picks up the beat from any source of music, whether it be a stereo, karaoke, live band (but not 66  Silicon Chip a dead band), etc. Speaking of bands, if you’re in one, this display will make your perfomance sparkle! How do you mount the lights? That’s really up to your ingenuity and your application. In our example, 12V halogen “downlights” are fitted pointing up (but at varying angles) into a squat wooden box about a metre long. The idea is to project the lights upwards against a white or pastel wall so that they throw patterns onto the wall. In a semi-darkened room, á lá a typical party, the effect is rather spectacular . . . psychedelic seventies, even. But if you don’t like that display, there’s nothing to stop you using the same basic circuitry to come up with whatever you wish. Want to make a “light box” – flashing lights inside an acrylic or Perspex-fronted box? No problem (in fact, you could get away with much lower wattage bulbs and therefore a cheaper transformer). Maybe you want to light up something specific – again, no problem. Because the lights operate from a safe 12V, you don’t have to be an electrician to install them. Gee, we just had a thought: most garden lights these days are 12V – now that would make an interesting garden! www.siliconchip.com.au Want more light? There’s nothing to stop you adding MOSFETs and lamps in parallel, as long as your transformer and bridge rectifier are rated for it. But more on this anon. Circuit operation With the exception of the input microphone, sensitivity control, the lamps themselves and the power supply (transformer and bridge rectifier), all of the circuitry is assembled on one small PC board. The circuit comprises four sections: the input audio signal processing, the sequence generator, the lamp drivers and the power supply. The input signal processing section has a low frequency filter and an amplifier section based on IC1a and IC1b. Audio signal is picked up by an electret microphone and is applied via a 1µF coupling capacitor to IC1b, an inverting preamp with a gain of 16. The low-pass filter components (at the input to IC1b) set the cut-off frequency to around 200Hz so only low frequency components (bass) pass to the next stage, an inverting amplifer based on IC1a. The gain of this amplifier depends on the setting of VR1, so this in effect becomes a sensitivity adjustment. The quiescent (no signal) DC output from IC1a is approximately 4V. Under this condition, the inputs of the Schmitt NAND gate IC2a will be a logic 1 and the output of this gate will be a logic 0. When an audio signal is applied, the output will vary up and down from the 4V quiescent voltage, going either more positive (to a maximum of 5V) or as low as zero for negative swings. www.siliconchip.com.au If the input voltage is sufficiently low, the input to the NAND gate will be a logic 0, giving a logic 1 at its output. In summary, no signal produces a logic 0 at the output of the NAND gate and negative signal swings at its input produce a logic 1. When IC2a has a logic 1 at its output, the 0.1µF capacitor at pin 5 of IC2b quickly charges via the 1N4148 diode and 4.7kΩ resistor. This produces a logic 1 at this point, enabling the oscillator, formed by IC2b, the 220kΩ resistor and .01µF capacitor to run. Its frequency is approximately 1kHz. The output from this oscillator is connected via a 1N4148 diode to the The display uses 12V, 50W halogen “downlights” such as these coloured ones from Jaycar or ordinary (white) ones you colour yourself. input of 7-stage ripple counter IC3, causing it to quickly count up, changing the states at its outputs as it does. The first four outputs of IC3 are used to drive a display comprising individual 12V halogen globes, via switching MOSFETS Q2-Q5. Under these conditions, each bass beat will produce a burst of 1kHz signal to clock the counter (IC3). The count at which it actually stops after each beat is random, thus producing a totally random display, updated by each bass beat. The oscillator is only enabled during the short time the audio signal is negative, causing bursts of oscillation on each bass beat, giving a new light display on each beat. Another oscillator is formed around IC2c, similar in configuration to that based on IC2b. The main difference is that the frequency of this oscillator is adjustable via VR2. This is used to clock the counter in the absence of an audio input signal. When an audio signal is present, the output of IC2b will be low often enough to allow the 1µF capacitor between +5V and pin 13 of IC2c to charge (via another 1N4148 diode and 10kΩ resistor). As a result pin 13 of IC2c will be low, thus disabling this oscillator. However when the music stops, the capacitor will discharge the 4.7MΩ resistor, allowing pin 13 to go to a logic 1 and therefore allow IC2d to oscillate. It takes approximately 5 seconds for the 1µF capacitor to discharge sufficiently to allow the input to this gate to reach a logic 1. Therefore, if the music stops for approximately 5 seconds, IC2c starts to oscillate and the counter automatically generates its own effectively random display sequence at a frequency set by VR2. The four least significant outputs of IC3 are connected to the gates of the power MOSFETS that are used to drive the lamps. These devices have no problems in driving a 50W halogen lamp without a December 2001  67 68  Silicon Chip www.siliconchip.com.au The circuit consists of four main parts – the input audio signal processing, the sequence generator, the lamp drivers and the power supply. The PC board component overlay above and a matching photograph to help you put it all together. Provision is made for VR1 (sensitivity) to be a preset mounted on the PC board but would more logically be an externally controllable pot, as shown here. It is shown as a linear type but if you have a log pot, use it! VR2 could also be external if you wish to have external speed control of the oscillator. www.siliconchip.com.au 1 220k 4.7k 4.7k 0.1F 4.7M VR1 1M LIN METAL PLATE 10k 1N 4148 1N 4148 D7 Q1 C C8050 MONO JACK SOCKET transformer/rectifier ratings. A 7805 regulator provides the low voltage supply to run the control circuitry. No heatsink is needed on the regulator but a reasonable heatsink is needed for the bridge rectifier, especially if four 50W bulbs are used. Construction As usual, we’ll start with assembling the electronics. After checking the PC board for any defects, solder in the lowest-profile components first – resistors, diodes, transistor, capacitors and the IC sockets (if used). If you have any doubt about the colour code on the resistors, check them before soldering them in with a multimeter (preferably a digital one). Also refer to the table showing the colour codes for both 4-band and 1F VR2 1M 10k LAMP1 _ B LAMP2 D _ G E 100 S B D3 + A D S Q3 1N 4148 IC2 4093 100F D2 10k S Q2 100 47k D4 + 4x IRFZ44 G 1k 10k 10k 10k IC3 4024 .0047F 4.7k D6 .01F Power supply A 300VA toroidal transformer supplies the power to drive the circuitry. It has two 12V <at> 12.5A secondaries which are connected in parallel, feeding a nominal 12V AC <at> 25A to a 35A bridge rectifier. The output from the rectifier is connected directly to the 12V halogen downlights. Because there is no filtering of the DC supply to the lamps, there is a lot of flicker in them. However, this doesn’t detract from the effect; in many ways, it enhances it. Output from the ripple counter is such that no more than three lights can be on at one time, with a combined current of about 12A (3 x 50W/12V). Therefore the transformer is operating well within its ratings. However, if you add extra MOSFETs and lamps as suggested above, consideration will need to be given to the D1 4.7M 100k 4.7k 10k .047F + 10F 10k 22k 4.7k 820 1 IC1 LF353 10F K D8 1N4004 0.1F 1N 4148 _ 1 1N4004 100k + A 100F 100F 1N 4148 + 1F 100k REG1 78L05 + + .0047F 1N 4148 heatsink; any more than this, though, and we would be tempted to fit each one with a small U-shaped heatsink. There is one minor complication concerning the ripple counter. It is possible for one of the counts to be 0000, a situation which would cause the display to turn off completely. This problem is solved by the addition of transistor Q1 and three 10kΩ resistors connected to the first three outputs of the ripple counter. If those three outputs are at logic 0, transistor Q1 is turned off and its collector voltage goes high, therefore a high is applied via diode D6 to the gate of MOSFET Q5, turning it on and lighting its lamp, irrespective of the state on the fourth output. Q5 is turned on (and its collector low) when any of the first three ripple counter outputs are at logic 1. + BR1 BR1 + _ Note that the photo and PC board layout both show an error involving the 10kΩ resistor immediately above the IC in the centre of the board. A correction for this is given at the end of the article (P72) but future production runs of PC boards may have this error corrected. Check the kit for any note to this effect. D5 Q4 1F LAMP3 _ G 100 S + C D Q5 D D LAMP4 _ G 100 5-band resistors. All semiconductors and the electrolytic capacitors are polarised, so make sure they go in the right way around. The same comment applies to the IC sockets. Finally, solder in the four MOSFETs and the regulator and place the ICs in their appropriate sockets. Check over your soldering and component placement. Power supply wiring Follow the wiring diagram for the power supply exactly, especially the mains side of the transformer. It is essential to get the colour coding correct on the windings – not just for your own safety but also ’cos it won’t work if you get it wrong! If you don’t use the transformer specified, check and double check the colour coding on the one you use. It is common that the mains side of the transformer has two wires the same colour while the secondaries are usually thicker wire. If you connect the secondaries in parallel but get no voltage out (and the December 2001  69 Here’s the “works” mounted in the custom-built case with the lid removed and the four lamp bases (which come with the gimbal fittings) disconnected. The main shot shows the business end while the inset shows the whole thing. transformer is OK!) you have connected the windings out of phase. Reverse one set of windings (not both!) and you should get your 12V AC output. While on the subject of transformers, Oatley Electronics have available some very cheap 9V+9V 250W toroidals which could be used as is (the halogen bulbs won’t be as bright and probably won’t last as long) or you could be really clever and add a few turns to each of the secondaries to bring them up to 12V out. As mentioned before, the bridge rectifier needs to be mounted on an adequate heatsink. We used a scrap of steel (actually an old mounting plate from a transformer). Of course you can also buy a wide range of heatsinks. To ensure maximum heat transfer between the rectifier and heatsink, some heat transfer compound should be smeared on the metal surface of the rectifier before it is bolted firmly to the heatsink. Hardware Our display used four 12V, 50W halogen “downlights” (mounted as “uplights”!) in a 1000mm (l) x 155mm 70  Silicon Chip (w) x 80mm (h) case made from 16mm chipboard or MDF. Standard gimbal halogen downlight fittings were used as these give a two-direction adustment, allowing you to aim the beams of light where they will be most effective. These are commonly available for about $10-12. In fact, Woolies sell them complete with transformer for about $20 but unfortunately the transformer will only handle one 50W globe. (But you would get a very nice 12V transformer which you could use for other projects!). Don’t be tempted to use an “electronic” halogen transformer. The gimbal fittings, which have an outside (front) diameter of about 100mm, require a mounting hole of about 90mm or so. They have two springs which hold them in place on the box. When you cut the holes in the box top, make sure you allow enough room for the springs to clear the box ends. Of course, all this assumes you are making a display the same as ours. If not, let your creative juices flow and do your own thing! The globes Coloured (red, green, blue and yellow) 12V 50W halogen globes are available from Jaycar Electronics These three pics show the gimbal fittings and how they are mounted in the case. Left, the fitting on its own. Above, one fitting mounted and below, all four fittings mounted in the box. www.siliconchip.com.au Follow this diagram and photo when wiring the transformer and bridge rectifier. All low voltage wiring must be capable of handling the currents involved. We have shown the wires going to the four halogen bulbs as “LAMP1+” etc. Of course, these bulbs are not polarised but it might be easier to think that one side of the bulb goes to +ve and the other, via the switching MOSFET on the PC board, to -ve. Parts List – Pardy Lites 1 PC board coded K170, 87mm x 62mm 1 16mm particle board case, approx 1000 x 140 x 80mm (see text) 4 halogen downlight gimbal fittings with wired ceramic lamp bases (sockets). 4 12V 50W coloured halogen downlight bulbs 1 toroidal transformer, 2 x 12V 12.5A secondaries 1 metal heatsink (see text) 1 2-metre 3-core mains power lead with 3-pin plug 1 mains cord clamp 1 3-way terminal block 1 electret microphone with cable and 3.5mm plug 1 3.5mm mono socket 1 mounting plate for microphone socket and sensitivity pot (see text) Suitable lengths 10A hookup wire (for wiring lights to PC board) Spaghetti insulation or heatshrink tubing Woodscrews (for assembling case and for mounting PC board and heatsink to case) 1 M3 screw, nut, star washer & solder lug Semiconductors 1 LF353 dual JFET op amp (IC1) 1 4093 quad 2-input Schmitt NAND gate (IC2) 1 4024 7-stage ripple counter (IC3) 2 1N4004 silicon power diodes (D1, D8) 6 1N4148 silicon signal diodes (D2- D7) 1 C8050 general-purpose NPN transistor (Q1) 4 IRFZ44 power MOSFETs (Q2-Q5) 1 78L05 5V low power positive regulator Capacitors 3 100µF 25VW PC mounting electrolytic 2 10µF 25VW PC mounting electrolytic 3 1µF 25VW PC mounting electrolytic 2 0.1µF MKT polyester 1 .01µF MKT polyester 1 .047µF MKT polyester 2 .0047µF MKT polyester Resistors (0.25W, 1%) 1 4.7MΩ 1 220kΩ 3 100kΩ 1 47kΩ 8 10kΩ 6 4.7kΩ 1 1kΩ 1 820Ω 4 100Ω 1 1MΩ potentiometer, taper unimportant (VR1) 1 1MΩ trimpot (VR2) www.siliconchip.com.au December 2001  71 We made our case from a piece of 1-metre long 16mm chipboard, with the dimensions as shown here. However, there is nothing to stop you from changing any or all of the dimensions –just so long as everything fits in without fouling other bits! Table 1: CAPACITOR CODES Value IEC Code EIA Code 0.1µF   100n   104 .047µF  47n  473 .01µF  10n  103 .0047µF  4n7  472 stores for about $7.00 each. That’s not bad value, considering ordinary white globes sell for only a dollar or so less. You can buy cheaper globes from a supermarket – about $4 each or so – but our experience with the life of these is not particularly good. Why are we mentioning white globes? Simple – they can be coloured. You can buy glass paint in many Table 2: RESISTOR COLOUR CODES    No.  1  1  3  1  8  6  1  1  1 Value 4.7MΩ 220kΩ 100kΩ 47kΩ 10kΩ 4.7kΩ 1kΩ 820Ω 100Ω 72  Silicon Chip 4-Band Code (1%) yellow purple greenbrown red red yellow brown brown black yellow brown yellow purple orange brown brown black orange brown yellow purple red brown brown black red brown grey blue brown brown brown black brown brown 5-Band Code (1%) yellow purple black yellow brown red red black orange brown brown black black orange brown yellow purple black red brown brown black black red brown yellow purple black brown brown brown black black brown brown grey blue black black brown brown black black black brown colours from craft stores which handles the heat of the globes without problems (we’ve used it many times on halogen bulbs in theatrical work). Or you can buy pieces of coloured glass from a glass supplier (or a leadlight supplier) and mount them over the front of the globes. The advantage of both these methods is that the range of colours is very much greater than the four “primary” colours above. Error on PC board As we went to press, we discovered an error on the PC board. It won’t stop the project working but doesn’t let it work as well as it should. The 10kΩ resistor immediately above IC2 connects to the cathode of D4 where it should connect to the anode. The easiest way to fix this is to solder the resistor under the PC board as shown below. This view is shown from the component side of the board (ie, looking through it with X-ray vision). SC Wheredyageddit? This kit was designed by Oatley Electronics who hold the copyright on the design and the PC board. Oatley Electronics have available the following kits/components: Short Form Kit: (PC board, all onboard components, bridge rectifier and metal heatsink): K170 $35.00 Contact Oatley Electronics on (02) 9584 3561, fax (02) 9484 3564 or via www.oatleyelectronics.com C o l o u r e d G l o b e s : Jay c a r, SL2741/2/3/4, $6.25 each Specified Transformer (12V/12V 300VA): Jaycar MT2130 <at> $83.95, Altronics M5512 <at> $72.50 Oatley 9V+9V 250VA Toroidal Transformer (see text) $30.00 www.siliconchip.com.au