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High-efficiency power supply For 1W Luxeon Star LEDs Looking for a highly-efficient switchmode power supply to run a 1W Luxeon Star LED from batteries? This easy-to-build design lets you use a pair of 1.5V “D” cells and includes brightness control to further extend the battery life. By PETER SMITH L AST MONTH, we described a simple linear supply for driving Lumileds’ 1W Luxeon Star LEDs. Designed with low cost and simplicity in mind, it is ideal for experimentation as well as general-purpose fixed lighting applications. The downside to this simplicity 24  Silicon Chip is that it’s not very energy efficient. However, for portable and emergency lighting applications, efficiency is of paramount importance. In a lowefficiency lighting setup, much of the available energy is consumed by the power supply itself, where it’s dissipated as heat. Conversely, an efficient supply transfers the majority of the input power to the output, thereby maximising battery life. This high-efficiency switchmode design can drive a single 1W Luxeon Star for more than 20 hours (continuous use) from a pair of alkaline “D” cells. It also includes a brightness control which, when set to the lower end of the scale, will extend useful battery life many times over. The PC board is the same size as two “D” cells side-by-side, making it ideal for use in lanterns, emergency lights, beacons, etc. We envisage it being used anywhere that a portable, reliable and ultra-long-life light source is required. It can drive green, cyan, blue and royal blue as well as white 1W LED www.siliconchip.com.au Main Features • • • • • High efficiency (>85%) Brightness control 2 x ‘D’ cell powered 20+ hours continuous use Drives white, green & blue Stars Fig.1: when the switch closes, inductor current increases with time, storing energy in its magnetic field. varieties, most of which are available locally from the Alternative Technology Association (see panel). Step-up DC-DC conversion In common with our 2-cell LED torch design (SILICON CHIP, May 2001), the circuit is based around a MAX1676 step-up DC-DC converter IC. These devices were originally designed for use in mobile phones and the like. Our circuit requires a step-up converter in order to boost the battery voltage, typically between 2.4V to 2.8V, to the higher 3.3V (nominal) required by the LED. Step-up conversion also assures maximum LED brightness over the lifetime of the batteries. To understand how this works, let’s first look at a few of the basics. Fig.2: when the switch opens, the magnetic field collapses. The inductor’s energy is discharged into the capacitor and load via the diode. Boosting the battery voltage The basic components of a step-up converter consist of an inductor, transistor (switch) and diode – see Fig.1. When the switch closes, the input voltage is applied across the inductor. The current flow (i) ramps up with time (t) and energy is stored in the inductor’s magnetic field. When the switch opens (Fig.2), an instantaneous voltage appears across the inductor due to the collapsing magnetic field. This voltage is of the same polarity as the input voltage, so the diode conducts, transferring energy to the output. Fig.3 shows where these basic parts fit in our design. As you can see, most of the step-up circuitry is contained within the MAX1676. Q1 acts as the switch, with Q2 replacing the series diode. Q2 acts as a synchronous rectifier, eliminating forward voltage losses and therefore improving efficiency. Output control The MAX1676 converter uses a current-limited pulse-frequency modulation (PFM) technique to maintain output regulation. Essentially, the switch is driven with a minimum www.siliconchip.com.au Fig.3: this diagram shows the basic elements of the power supply. Most of the step-up circuitry is contained within the MAX1676 chip, including the switching transistor and rectifier. Fig.4: On the bench, our prototype powered a Star for over 20 hours on “D” size alkaline cells. Even at 0.6V/cell, the supply was still pumping out more than half a watt (about 160mA). Almost full power is delivered to the LED down to 1.8V. This means that you’ll get high brightness over the entire life of a set of rechargeables. Converter efficiency was measured at 90.1% with a 3.0V input, with a total circuit efficiency (input to output) of 85.5%. pulse width, variable-frequency signal (up to 500kHz), which increases as battery voltage decreases. For a detailed description of its operation, check out the Maxim datasheet, available from www.maxim-ic.com. When the battery voltage falls below about 1.8V, the output power decreases markedly due to the high input to output voltage differential (see Fig.4). For example, with only 0.5V per cell, a step-up ratio of about 3.3:1 would be required to achieve full power. Assuming about 75% efJanuary 2004  25 Fig.5: the complete circuit diagram for the power supply. Two CMOS 7555 ICs modulate LED brightness by controlling the step-up converter’s shutdown pin. ficiency, this means that the supply would have to pull around 1.4A from the (already) flat batteries. And with increasing cell resistance, this simply wouldn’t be possible. As you can see, reducing output power towards the end of battery life is actually desirable, as it allows the supply to almost drain a pair of alkaline cells. This reduces wastage and provides a useful amount of light for much longer. Filament lamp circuits can’t hope to match this result. To prove the point, try your torch batteries with this supply when they’re almost knackered – you’ll be amazed at the brightness of the LED compared to the incandescent bulb! Circuit description The complete circuit diagram for the power supply appears in Fig.5. It consists of two main elements – the step-up converter (no surprises here) and two 7555 timers (IC1 & IC2). The timers are part of the brightness control circuit, which we’ll come back to in a moment. First, let’s complete the description of the step-up converter. In a standard application, the MAX1676 (IC3) requires very little external circuitry to form a complete step-up power supply. However, in order to regulate output current (rather than output voltage) for our LED load, we’ve added a few components to the feedback loop. Transistors Q2 & Q3 amplify the current sense voltage developed across the parallel 1Ω resistors. These two transistors are connected in a current mirror configuration, with Q2’s base and collector connected to IC3’s 1.3V reference output. Therefore, a known current flows through Q2. This is used to generate 175mV at the emitter of Q2 and by current mirror action, Q3 attempts to maintain the same voltage at its emitter. The MAX1636’s internal error amplifier compares the feedback voltage on pin 1 with a 1.3V reference. If it is less than 1.3V, the voltage at the output (pin 10) is increased, whereas if it is more, the voltage is decreased. This 26  Silicon Chip www.siliconchip.com.au has the effect of increasing or decreasing the current through the LED. Q3’s collector controls the voltage on the feedback pin, acting much like a common base amplifier. When its emitter voltage equals 175mV (for 350mA through the LED), the collector will be at 1.3V and the loop is in regulation. Trimpot VR1 provides a means of adjusting the LED current to the desired 350mA, thus accommodating component tolerances. Zener diode ZD1 clamps the output to a maximum of 6V to protect IC3 should the LED fail or be inadvertently disconnected. The 5.6nF capacitor between the output and feedback pins ensures loop stability. Low-battery detection Both rechargeable (NiCd/NiMH) and alkaline battery types can be used with the power supply. Alkaline batteries are a good choice for intermittent use, as they have a low self-discharge rate. On the other hand, rechargeables work well for continuous use. Their lower internal resistance and relatively flat discharge curve provides a higher average level of light output over the discharge period compared to non-rechargeables. Unlike non-rechargeables, it’s important not to totally discharge NiCd and NiMH cells. Repeatedly doing so substantially reduces cell life. To help avoid this problem, the power supply includes low-battery indication. When the voltage on the MAX1626’s low-battery comparator input (pin 2) falls below an internal reference voltage (1.3V), the comparator’s output (pin 3) goes low. This switches on transistor Q4, illuminating the “Low Battery” LED. A simple voltage divider connected to the comparator input sets the trip point to about 1.8V (0.9V per cell). When running on alkalines, the LED provides a useful indication of battery condition. Brightness control The brightness of a LED can be varied by varying the current through it. However, rather than varying the absolute level, Luxeon recommends pulse-width modulating (PWM) it instead. This results in a much more colour-uniform light output, right down to minimum brightness. www.siliconchip.com.au Fig.6: this is the waveform across the LED with VR1 at mid-position. A 180Hz PWM frequency ensures that the LED appears to be always on. Note that the waveform is not a perfect square wave due to the time constant of the output filter capacitor. To realise PWM control, it’s just a matter of switching the LED current on and off at a fixed frequency and varying the duty cycle (on/off time) to vary the brightness. By using a high enough frequency, the switching effects are invisible due to the long persistence of the phosphors (in white LEDs) and the natural integration of the eye. On the power supply board, two 7555 CMOS timers (IC1 & IC2) form the core of the PWM circuitry. The first 7555 (IC1) is configured as a free-running oscillator. Its frequency of oscillation (about 180Hz) is set by the 680kΩ and 100Ω resistors and the 10nF capacitor on pins 2, 6 & 7. The 100Ω resistor in the capacitor’s discharge path is much smaller than the 680kΩ resistor in the charge path, resulting in a very narrow positive pulse from IC3’s output. This is used to trigger the second 7555 (IC2). IC2 is configured as a monostable, with the positive pulse width on the output (pin 3) made variable by 1MΩ trimpot VR1. Near the maximum pot setting, the positive pulse width is longer than the period of IC1. This is where transistor Q1 comes in – it is needed to discharge the 5.6nF timing capacitor, effectively retriggering IC2 and allowing a 100% duty cycle at the output. The fixed frequency, variable pulse width (PWM) output from IC2 is applied to the MAX1676’s shutdown pin. When this pin goes low, the chip stops switching and goes into low-power mode. Fig.6 shows the waveform across the LED at VR1’s mid position. As shown, this results in a 55% duty cycle or thereabouts. Power for the 7555 timers and associated circuitry is provided via Schottky diodes D2 & D3. By sourcing power from the output as well as the input sides of the circuit, we ensure that the signal level applied to the MAX1676 shutdown pin tracks the output voltage and remains valid under all conditions. Readers familiar with last month’s Experimenter’s Power Supply circuit may wonder why we’ve used a different (and more complicated) PWM circuit for this design. The answer is simple – this circuit must operate at much lower voltages (down to 1V), and therefore we cannot afford the diode losses in the timing network. Note also that we’ve used 7555 (CMOS) timers rather than 555 (NMOS) versions, which saves power and ensures lowvoltage operation. Reverse battery protection Most SILICON CHIP designs include a diode in series with the DC input for protection against accidental January 2004  27 Fig.7: three SMD components go on the bottom side of the PC board and these must be mounted before anything else. Fig.8: a close-up section of the bottom side of the board, showing just the area of interest for the SMD components. Note how IC3’s leads are positioned precisely in the centre of the rectangular pads. Fig.9: follow this diagram when assembling the top side. Don’t miss any of the links (there are 10 in all), and take care with the orientation of the ICs, diodes and electrolytic capacitors. You will need fine (0.5mm) solder and a temperature-controlled iron to solder in the SMD components. • Temperature-controlled soldering iron. • 0.8mm (or smaller) micro-chisel soldering iron tip. • 0.76mm desoldering braid (“SoderWick” size #00). • 0.5mm (or smaller) resin-cored solder. • Needle-nose tweezers. • Damp sponge for tip cleaning. • Small stiff brush & alcohol/cleaning solvent. • Magnifying glass and bright light for inspection. In addition, the job is made easier with the aid of SMT rework flux, which is available in a 10cc syringe from Altronics (Cat. H-1650). Note: the ICs used in this project are static-sensitive. We recommend the use of a grounded anti-static wrist strap during board assembly. Bottom side assembly supply reversal. However, a series diode in this circuit would seriously compromise efficiency and running time. Therefore, we’ve settled for a reverse diode (D1) across the input terminals. A reversed supply will cause large current flow through D1 and, in the case of high-energy rechargeable cells, will quickly destroy it. In many cases, the diode will fail “short circuit”, protecting the expensive (and hard to replace!) step-up converter IC. This is assuming, of course, that the batteries are only momentarily reversed. Leaving them connected for any length of time will cause heat damage to the board, or worse. If you’re concerned about this possibility, then 28  Silicon Chip install a 2A quick-blow fuse in series with the positive battery lead. SMD soldering gear Referring to the various photos and diagrams, you can see that the assembly includes three surface-mounted devices (SMDs) – the MAX1676 converter IC and two 100nF chip capacitors. The MAX1676 is supplied in a tiny “uMAX10” package with 0.5mm lead spacing. Soldering this little device can be a challenge – even for experienced constructors. It must be mounted first, before any of the through-hole components. The following items should be considered essential to the task: Begin by checking the PC board for defects. In particular, check for shorts between pads and tracks around IC3’s mounting site. The magnifying glass and bright light will come in handy here. Use your multimeter to verify isolation between any suspect tracks. Next, thoroughly clean the board with a lint-free tissue (or similar) moistened with alcohol or cleaning solvent. The rectangular IC pads must be pre-tinned and perfectly smooth (free of solder “lumps”). If you have SMT rework flux, apply a thin film to the mounting pads. Using needle-nose tweezers, grasp the MAX1676 by its ends and inspect it closely under a magnifying glass. Make sure that the leads are all perfectly formed, with equal spacing and alignment in the horizontal plane. In www.siliconchip.com.au other words, they must all line up and make contact with their respective pads. Carefully adjust individual leads if necessary (you may need a second pair of tweezers). Place the device in position on the board, with pin 1 aligned as shown in Figs.7 & 8 (double-check this!). Now, using your magnifying glass, make sure that the device is perfectly aligned over the rectangular pads. This is very fiddly and requires patience and a steady hand! Next, clean your iron’s tip and apply a small quantity of solder to it. With your third hand, apply light downward pressure on the MAX1676 to hold it in position. If the package moves (which it is liable to do), reposition it and start over. Apply the tip to one of the IC’s corner mounting pads, touching both the pad and IC lead simultaneously. The solder should “blob”, tacking the chip in place. Check that the IC is still perfectly aligned over the rectangular pads. If it’s not, carefully remove it and try again. If you find that the package moves whenever you try to tack the first pin, then there is an alternative method. First, position the IC as described above and apply your iron to the track/ pad just in front of the IC lead (don’t touch the lead). Next, feed a little solder to the tip, and it should flow along the track/pad and up over the lead. This method is more successful when additional flux is used. Now repeat the same procedure for the diagonal corner, effectively securing the IC in position. Check alignment This view shows the fully assembled PC board. Take care to ensure all parts are installed correctly. again, as we’re about to make this position permanent! If you have SMT flux, apply it to all IC leads and the adjacent tinned copper areas. You can now solder the remaining eight leads. Apply heat to both the pad and lead simultaneously and feed a minimum amount of solder to the joint. Do not apply heat to any lead for more than two seconds! Despite your best efforts, you’re certain to get “blobs” of solder and perhaps even solder bridges between adjacent pins. Don’t despair – this can be fixed! Again, if you have SMT flux, apply a minimum amount to all IC leads and adjacent PC board copper. Next, position a length of fine desoldering braid across the ICs leads and heat with a freshly tinned iron. Table 2: Capacitor Codes Value μF Code 100nF 0.1µF 10nF .01µF 5.6nF .0056µF EIA Code IEC Code   104 100n   103   10n   562   5n6 Table 1: Resistor Colour Codes o o o o o o o o o o o o o o o No.   1   2   1   1   1   1   1   1   2   1   1   2   2   1 www.siliconchip.com.au Value 680kΩ 160kΩ 100kΩ 62kΩ 47kΩ 27kΩ 6.8kΩ 3kΩ 470Ω 270Ω 200Ω 100Ω 1Ω 10Ω 5W 4-Band Code (1%) blue grey yellow brown brown blue yellow brown brown black yellow brown blue red orange brown yellow violet orange brown red violet orange brown blue grey red brown orange black red brown yellow violet brown brown red violet brown brown red black brown brown brown black brown brown brown black gold gold not applicable 5-Band Code (1%) blue grey black orange brown brown blue black orange brown brown black black orange brown blue red black red brown yellow violet black red brown red violet black red brown blue grey black brown brown orange black black brown brown yellow violet black black brown red violet black black brown red black black black brown brown black black black brown brown black black silver brown not applicable January 2004  29 Fig.10: the full-size PC board pattern. Check your board carefully for etching defects before installing any of the parts. Parts List 1 PC board, code 11101041, 68mm x 62mm 1 L8 ferrite toroid, 19 x 10 x 5mm (L1) (Jaycar LO-1230) 2 2-way 2.54mm terminal blocks (CON1, CON2) 1 3-way 2.54mm SIL header (JP1) 1 jumper shunt 2 8-pin IC sockets 1 2 x “D” cell holder 1 SPST power switch to suit (2A contacts) (S1) 1 300mm length (approx.) 1mm enamelled copper wire 4 M3 x 10mm tapped nylon spacers 4 M3 x 6mm pan head screws Semiconductors 2 7555 CMOS timers (IC1, IC2) 1 MAX1676EUB step-up DC-DC converter (IC3) (Altronics) 1 1N5404 3A diode (D1) 2 BAT46 Schottky diodes (D2, D3) (Jaycar ZR-1141) 2 PN200 transistors (Q1, Q4) 2 2N3904 transistors (Q2, Q3) 1 3mm high-intensity red LED (LED1) 1 1W Luxeon Star LED (white, green, cyan, blue or royal blue) Capacitors 2 100µF 50V low-ESR PC electrolytic (Altronics R-6127) 1 100µF 16V PC electrolytic 2 100nF 50V monolithic ceramic 2 100nF 50V SMD chip (0805 size) (Altronics R-8638) 3 10nF 63V MKT polyester 2 5.6nF 63V MKT polyester Resistors (0.25W, 1%) 1 680kΩ 1 6.8kΩ 2 160kΩ 1 3kΩ 1 100kΩ 2 470Ω 1 62kΩ 1 270Ω 1 47kΩ 1 200Ω 1 27kΩ 2 100Ω 2 1Ω 0.25W 5% 1 10Ω 5W 5% (for testing) Trimpots 1 1MΩ miniature horizontal trimpot (VR1) (Altronics R-2486B) 1 5kΩ miniature horizontal trimpot (VR2) (Altronics R-2479B) Miscellaneous Hot melt glue or neutral cure silicone sealant 30  Silicon Chip You will probably find that it’s easier to heat two or three leads at once. The idea is to remove all of the solder blobs and bridges, leaving bright and wellformed solder fillets between leads and pads. As before, do not apply heat to any lead for more than two seconds and allow about 20 seconds between applications for the IC to cool! Once you’ve done that, remove all flux with the cleaning fluid and brush and inspect the result under a magnifying glass. Redo any joints as necessary. Once you’re happy with your work, use a multimeter to make sure that there are no shorts between adjacent pads and tracks. This step is very important; a hairline solder bridge can be difficult to spot by eye! Before moving on to the top side of the board, solder the two 100nF chip capacitors in place (see Figs. 7 & 8) and install the insulated wire link. The link can be fashioned from a length of 0.7mm tinned copper wire insulated with heatshrink tubing or similar. You’ll need to form a gentle bend into the link so that it doesn’t obscure the holes for the capacitor leads. Trim the link ends flush with the surface on the top side of the board. Top side assembly Now for the top side assembly. First, fit an M3 x 10mm tapped Nylon spacer to each corner of the PC board. This will help to protect the SMD parts while you’re installing the remaining parts. Using the overlay diagram (Fig.9) as a guide, begin by installing all the wire links using 0.7mm tinned copper wire. Note that some of these links go underneath components (IC1 & IC2, for example), so they must be installed first! Next, install all of the 0.25W resistors, followed by diodes D2, D3 and ZD1. Be sure to align the cathode (banded) ends as shown. All remaining parts can now be installed in order of height, leaving the large 100µF capacitors and inductor L1 until last. Be careful not to mix up the two different transistor types. Winding the inductor The inductor (L1) must be handwound. To do this, wind 6.5 turns of 1.0mm enamelled copper wire onto the specified ferrite toroid. The wire must be wound as tightly as possible and spaced evenly over the core area (see Fig.9 and the photos). The start and finish should be spaced about one turn apart. Trim and bend the wire ends to get a neat fit into the PC board holes. That done, use a sharp blade to scrape the enamel insulation off the wire ends. The ends can then be tinned and the completed assembly slipped into position and soldered in place. You can now permanently fix the inductor to the PC board using a few blobs of hot-melt glue or neutral cure (non-acetic) silicone sealant. Finally, install the two 100µF electrolytic capacitors. Note that they go in opposite ways around, so be sure to align the positive leads as indicated on the overlay diagram. Test and calibration Don’t be tempted to hook up your LED just yet! First, the supply must be checked for correct operation and the output current set. To do this, first connect a 10Ω 5W resistor directly across the output terminals. Next, hook up your battery holder’s flying leads to the input terminals, making sure that you have them the right way around. Use the overlay diagram (Fig.9) to determine the correct polarity. Note that the leads to the battery holder should be kept as short as www.siliconchip.com.au BITSCOPE AD 9/10/03 1:38 PM Page 1 Digital Oscilloscope Logic Analyzer + from 5 $59 ANALOG = DIGITAL Convert your PC into a powerful Scope and Logic Analyzer! Now you can analyze electronic circuits in the analog and digital domains at the same time. BitScope lets you see both analog AND digital logic signals to find those elusive bugs. USB and Ethernet connectivity means you can take BitScope anywhere there is a PC or Network. BitScope Hardware • 100MHz Input BW • 40MS/s Sample Rate • Dual 32K Buffers • 4 Analog Inputs • 8 Digital Inputs • Waveform Generator • SMART POD Probes www.siliconchip.com.au BitScope Software • Windows or Linux • TCP/IP Networking • Advanced DSP • Digital Scope • Analog Scope • Logic Analyzer • Spectrum Analyzer Applications • Electronics Labs • Remote data logging • Engineering students • Scientific research • Robotics and control www.bitscope.com USB or Network connection to Windows and Linux PCs! January 2004  31 Silicon Chip Binders REAL VALUE AT $14.95 PLUS P & P These binders will protect your copies of S ILICON CHIP. They feature heavy-board covers & are made from a dis­ tinctive 2-tone green vinyl. They hold 12 issues & will look great on your bookshelf. H 80mm internal width H SILICON CHIP logo printed in gold-coloured lettering on spine & cover H Buy five and get them postage free! Price: $A14.95 plus $A10.00 p&p per order. Available only in Aust. Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or call (02) 9939 3295; or fax (02) 9939 2648 & quote your credit card number. Use this handy form Enclosed is my cheque/money order for $________ or please debit my  Visa    Mastercard possible. We’d also recommend replacing the light duty leads (supplied pre-wired on most holders) with heavy-duty multi-strand cable. The next step is to install a jumper shunt on pins 2-3 of JP1 to disable brightness control and to set VR2 to its centre position. Now hold your breath and plug in a pair of fresh alkaline batteries. Measure the voltage drop across the 10Ω resistor. If the supply is working properly, your meter should read near 3.5V. If it is much lower (say, around 2.3V), then the step-up converter is not doing its job. Assuming all is well, adjust VR2 to get 3.5V across the resistor. LED mounting The Luxeon Star’s emitter and collimating optics are factory-mounted on an aluminium-cored PC board. In most cases, no additional heatsinking is required. However, a small heatsink reduces junction temperature and therefore ensures maximum LED life. Just about any small aluminium heat­ sink with a flat surface large enough to accommodate the Star’s 25mm footprint can be pressed into service. For example, an old 486 PC processor heatsink would probably be ideal. A light smear of heatsink compound between the mating surfaces will aid heat transfer. We’ve not provided any specific mounting details here, as they will depend entirely on your application. Keep in mind that the heatsink surface must be completely flat so as not to distort the LED’s PC board when the mounting screws are tightened. You should also provide strain relief for the connecting wires. Note that this supply is suitable for use with white, green or blue stars but not red or amber. This is because of the lower forward voltage of the latter varieties (2.3V min. versus 2.8V). With maximum input voltage, the output of the supply could exceed a red/amber LED’s forward voltage, with the result being loss of regulation and probable damage to the LED. LED hook-up Wire up your Star with light to medium-duty multi-strand cable. Try to keep the cable length under 150mm or so. A small copper “dot” near one of the corner pads indicates the anode (+) side of the LED. Next, disconnect the 10Ω “test” resistor and replace it with the LED leads. That done, you can power up and measure the voltage drop across the paralleled 1Ω resistors. These are situated next to the output connector (see Fig.9). If necessary, readjust VR2 to get a reading of 175mV. As described earlier, this sets the LED current at full power to 350mA. By the way, don’t stare directly into the LED beam at close range, as it is (according to Luxeon) bright enough to damage your eyesight! Note: the current calibration procedure described above should only be performed after installing a fresh set of alkaline batteries. If you’re using a DC power supply instead of batteries, set the input voltage to 2.80V (never exceed 3.0V!) Brightness control To use the brightness control function, move the jumper shunt to the alternate position (JP1, pins 1-2 shorted). By rotating VR1, it should now be possible to vary the LED intensity all the way from dim to maximum brightness. If required, VR1 can be mounted away from the PC board. Keep the wire length as short as possible (say, no more than about 50mm) and twist the three connecting wires tightly together. If you’re using a plastic case, then the metal body of the pot will probably need to be connected to battery negative to reduce the effects of SC noise pickup. Card No: _________________________________ Card Expiry Date ____/____ Signature ________________________ Name ____________________________ Address__________________________ __________________ P/code_______ 32  Silicon Chip Where To Get Parts & Stars A complete kit of parts for this project is available from Altronics for $34.95 (doesn’t include 1W Luxeon Star LED). 1W Luxeon Star LEDs are currently available from Prime Electronics on the web at www.prime-electronics.com.au or phone (02) 9746 1211. You can also get them from the Alternative Technology Association at www.ata.org.au, phone (03) 9388 9311. Detailed technical information on Luxeon Star LEDs can be obtained from the Lumileds web site at www.lumileds.com www.siliconchip.com.au