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By JIM ROWE Starship Enterprise Door Sounder Here’s a project especially for trekkies. At the closure of remote switch contacts, it recreates that distinctive “ssshhhhhhh-thump” sound of the sliding doors opening or closing on the “Starship Enterprise”. Use it for generating sound effects for your own sci-fi movies or for hooking up to a bedroom or wardrobe door so you can pretend you’re aboard the “Enterprise” in deep space, going where no man has gone before! G ENE RODDENBERRY’S original TV series of “Star Trek” broke quite a bit of new sci-fi ground in its day, with imaginative thoughtprovoking stories and a collection of interesting characters: Captain James T. Kirk, science officer Spock, engineer Scotty (“you canna’ change 92  Silicon Chip the laws of physics, Jim”) and so on. Small wonder it spawned a number of spin-off movies and a follow-on series, along with a huge following of ‘trekkie’ fans who seem just as dedicated today as they were 30 years ago – no doubt helped by the release of all the original episodes on DVD. Of course, along with those original episodes, many keen trekkies also like to acquire “Star Trek” memorabilia: replicas of the costumes worn by the “Enterprise” crew, copies of Mr Spock’s pointy ears, fake phaser guns and so on. They also like being able to generate some of the distinctive siliconchip.com.au Fig.1: the circuit uses an HK828 sound recorder chip (IC1) to store two different “Starship Enterprise” door sounds. This drives audio amplifier stage IC2 to replay one of these sounds when switch S1 or S2 is momentarily closed. sound effects which helped make the first series so memorable. So if you have a friend or relative who’s one of these dedicated trekkies, you might want to build this project for them – or for yourself! It recreates the “ssshhhHHHh-thump” sound that always accompanied the sliding power doors opening or closing on the “Starship Enterprise” and can be triggered by either pressing a pushbutton or closing the contacts of an external switch (eg, a reed switch activated by a bedroom door or sliding wardrobe door). It’s also quite easy to build and can be operated from a 9V battery or 12V plugpack. Coming up with the sound When I was first asked (by Jaycar) to develop this project, I initially spent some time watching old “Star Trek” episodes and listening to the sound of “Starship Enterprise” doors opening and closing (hard work, but somebody siliconchip.com.au had to do it!). I also examined the shape of the waveform envelope and did a few spot checks of the frequency components present at various points in the waveform. Armed with this information, I then set to work and came up with quite a fancy circuit which generated a burst of white noise, shaped its envelope to produce a “ssshhhHHHh” sound and then mixed in some low-frequency components to produce the required thump as the door closed at the end. Well, to cut a long story short, it did work and the sound it made was a reasonable reminder of an Enterprise door operating. Since this sound was less than one second long, it could easily be recorded in a solid-state voice recorder chip, like the HK828 device used in the Voice Recorder module described in the May 2005 issue of SILICON CHIP. That way, constructors would not have to build the original circuit which was rather complicated. Instead, the synthesised sound produced by that circuit would be pre-programmed into HK828 devices and supplied with the kits (Jaycar has copyright – see panel). In fact, the HK828 is capable of recording about 30 seconds of sound at its highest sampling rate, so it can easily store as many as four different sound “files” like the “Starship Enterprise” door sound. So that’s the basis of this project. It’s essentially a stripped-down version of the May 2005 Voice Recorder, able to play back two slightly versions of the “Starship Enterprise” door sound from pre-programmed HK828 chips. How it works Fig.1 shows the circuit diagram of the unit. It’s very similar to the Voice Recorder, the main difference being that here we’re using the HK828 chip for playback only. That’s because it June 2006  93 Fig.2: this block diagram shows what’s inside the HK828 sound recorder chip. The circuit blocks associated with recording are not used in this particular application, since we are using the playback function only (the chip is supplied pre-recorded). will be supplied pre-programmed with the sound effect “recordings”. Because the HK828 chip still forms the functional heart of the project, we’ll give you a quick rundown on what’s inside it. You can see the chip’s basic architecture from the block diagram of Fig.2. We won’t worry about the internal circuit sections used for recording, because they’re not being used in this case (if you want to understand how they work, refer to the May 2005 article). In fact, the only section on the lefthand side of Fig.2 we’re making use of here is the “Internal Oscillator”. This section actually generates the HK828’s sampling clock for playback, as well as recording. Its frequency is determined by an external resistor (from pin 7 to ground), which in this case has a value of 22kW to give a sampling rate of about 8.7kHz – about as fast as the HK828 can operate, to achieve its best audio bandwidth. Now although the recorded audio is stored as samples inside the HK828, this is done using an analog sampleand-hold system rather than the more common digital sampling. This is because it stores the samples in an array of 262,144 (256K) Flash EEPROM analog storage cells, each of which can store any of 256 different voltage 94  Silicon Chip levels. This gives the equivalent of 8-bit digital recording. As shown in Fig.2, the recording and playback of samples in the storage array is controlled by analog write and read circuits, along with the message control and message addressing circuits. When a recorded sound is being played back, the signals are fed through a low-pass filter to remove sampling noise and then fed to the internal output amplifier. The rest of the circuitry inside the HK828 chip is used for overall device control and mode switching, etc. As mentioned above, the HK828 can be configured to store and play back either a single sound “recording” (like a tape recorder) or a fixed number of shorter recordings. In this case, it’s configured to play back either of two shorter recordings. Main circuit Now let’s go back to the main circuit – see Fig.1. As shown, the replayed audio signal is taken from pin 14 of the HK828 (IC1) and fed via a 10kW series resistor and 10mF capacitor to trimpot VR1 which is used to adjust the output volume. The audio signal is then fed via a 2.2mF capacitor to the non-inverting input of IC2, a TDA1905 audio power amplifier. This is config- ured to have a voltage gain of 100, as set by the 10kW and 100W resistors in the negative feedback divider. IC2 can deliver about 800mW of audio power to an 8W speaker with a 9V DC supply and about 1.4W of power with a 12V DC supply – enough to produce a convincing sound level from the 57mm mini-speaker. Of course, it will produce an even more convincing sound from a larger speaker. As stated, the HK828 chip can be configured to split its internal memory into either two or four chunks. This is done by connecting either one or the other of its MSEL pins (pins 24 & 25) to ground. In this case, the device is configured for two recorded sounds by connecting pin 24 to ground, via a small copper track on the underside of the PC board. To trigger the HK828 into replaying one of its sound recordings, a negativegoing pulse with a duration of about 500ms is applied to one of its trigger inputs – ie, M1-bar to M4-bar. In this circuit, only M1-bar (pin 1) and M2bar (pin 2) are used, to replay the two recorded sounds. The actual triggering pulses are provided by closing the contacts of either remote switch S1 or remote switch S2. In each case, this applies a negative-going pulse to the corresiliconchip.com.au Fig.3 (left: follow this parts layout diagram and the photo above when installing the parts on the PC board. The LED can either be mounted on the PC board (and used for testing purposes only) or it can be mounted on the front panel and connected to the PC board via flying leads. Make sure that all polarised parts are correctly installed and that IC1’s pins all go into the socket and are not bent underneath the device or splayed out. sponding chip input via an associated 2.2mF capacitor. The capacitor then subsequently discharges again via its associated 220kW resistor when the switch contacts open again. This prevents the chip from being repeatedly triggered if the switch contacts remain closed. In fact, they must be opened and the capacitor allowed to discharge, before being closed again in order to retrigger the circuit. The main idea of this is to allow you to use remote reed switches or micro­ switches, so that the unit can be wired to operate automatically when you open or close a bedroom door, etc. When the HK828 is playing back a sound, it switches its Strobe-bar pin (pin 22) low once every 200ms or so. This drives LED1 via a 680W current-limiting resistor, so that the LED “blinks” during playback. Power supply The HK828 has a maximum supsiliconchip.com.au ply voltage of 6V. As a result, a 7806 3-terminal regulator (REG1) is used to derive a +6V rail from the 9-12V DC supply used to power audio amplifier IC2. Diode D1 prevents damage due to accidental reversed polarity. The 9-12V DC source used to power the project can be either a plugpack or battery. This must be capable of supplying about 25mA continuously when the circuit is at idle and up to 150mA or so when it is producing sound. Construction Apart from the loudspeaker (and possibly LED1), all the components are mounted on a PC board coded 01206061 and measuring 111 x 57mm. This board has rounded corner cutouts at one end, so that it fits snugly inside a standard UB3-size jiffy box at that end. The speaker is mounted on the box lid, while the 9-12V DC power source is fed in through a 2.5mm concentric DC connector mounted on the PC board. Also on the board is a small terminal block. This accepts the leads from remote trigger switches S1 & S2, the leads entering via small holes in the side of the box. Fig.3 shows the parts layout on the PC board. Begin by fitting two PC board terminal pins at one end of the board for the connections to the speaker. Once these are in, you can also fit connector CON1 and the small terminal block. Next, fit trimpot VR1, making sure you orientate it correctly, then fit the resistors. Follow these with the capacitors, beginning with the small monolithic ceramics and then working your way through the MKT, tantalum and aluminium electrolytic types. Remember that while the monolithic and MKT types are not polarised, the tantalum and aluminium electrolytics are indeed polarised and must June 2006  95 (as in Fig.3). If you choose the latter option, you will have to drill an extra hole in the front panel and secure the LED using epoxy adhesive. Note that the flying leads for LED1 are soldered directly to the board rather than to PC board pins. The final component to fit to the board is regulator REG1, which is mounted horizontally. To do this, first bend its leads downwards by 90° about 6mm from the regulator package. That done, fasten it in place using an M3 x 6mm machine screw and nut before soldering its leads to their respective board pads. The PC board assembly is now complete and you can fit the wires used to connect the speaker. These speaker wires can be made from a 110mm length of light-duty figure-8 flex. Par t s Lis t 1 plastic utility box, UB3 size (130 x 67 x 44mm) 1 PC board, code 01206061, 57 x 111mm 1 57mm mini speaker, 8-ohm impedance 1 3-way screw terminal block, PC-mount 1 28-pin IC socket, 0.6-inch PCmount 1 2.5mm concentric DC connector, PC-mount (CON1) 2 PC board terminal pins 4 M3 x 10mm machine screws, countersink head 1 M3 x 6mm machine screw, round head 9 M3 nuts 1 20kW horizontal trimpot (VR1) Semiconductors 1 HK828 sound recorder chip, pre-recorded (IC1) 1 TDA1905 audio amplifier (IC2) 1 7806 +6V regulator (REG1) 1 5mm green LED (LED1) 1 1N4004 power diode (D1) be fitted the correct way around. The wiring diagram indicates the positive lead of each polarised capacitor with a small ‘+’. One point to watch with the 100nF capacitors is that two of these are multilayer monolithic ceramics, while the remaining four are the larger rectangular MKT type. The monolithic capacitors go in the indicated positions at either end of IC1, while the MKT types go in the remaining positions. Once the capacitors are all in position, fit diode D1. This is again polarised, so make sure you orientate it as shown. That done, install IC2, which Capacitors 1 2200mF 16V RB electrolytic 1 1000mF 16V RB electrolytic 1 220mF 10V RB electrolytic 1 100mF 16V RB electrolytic 1 47mF 16V RB electrolytic 2 10mF 10V RB electrolytic 1 4.7mF 25V tantalum 4 2.2mF 25V tantalum 1 220nF MKT metallised polyester 4 100nF MKT metallised polyester 2 100nF multilayer monolithic Resistors (0.25W 1%) 3 220kW 2 100W 6 22kW 1 47W 2 10kW 1 1W 1 680W Final assembly The PC assembly is now ready to be mounted into the box. Before doing so though, give it a careful inspection to make sure that you haven’t made any bad solder joints or left solder bridges shorting between tracks or IC pads. It’s also worth double-checking that you’ve fitted all polarised parts with their correct orientation. Once you’re satisfied that everything is OK, the board can be mounted inside the box. This is secured using four M3 x 10mm countersink-head machine screws, which are passed up from the underside and secured using star lockwashers and M3 nuts which also act as spacers. The board is then lowered onto these “spacers” and secured using four more M3 nuts. The speaker is mounted on the rear of the box lid, behind an array of holes which are provided to let the sound out. It is held in place using “Araldite” or similar epoxy cement, which is applied to the front of the speaker’s outer rim before introducing it to the Where To Buy A Kit This project was sponsor­ ed by Jaycar Electronics, who own the design copyright. A complete kit of parts is available from Jaycar for $39.95 – Cat. KC-5423. should be soldered directly into the board. This is important for its stability and also improves heat dissipation. By contrast, IC1 plugs into a 28-pin socket. Be sure to install this socket with its “notched” end towards the 47W resistor, to guide you in plugging in the HK828 chip. When the socket pins are all soldered to the board pads underneath, you can plug IC1 into the socket. Be sure to do this without damaging any of its pins. LED1 can either be mounted on the PC board (as in the prototype), or it can be mounted on the front panel and connected to the PC board by flying leads Table 1: Resistor Colour Codes o o o o o o o o No.   3   6   2   1   2   1   1 96  Silicon Chip Value 220kW 22kW 10kW 680W 100W 47W 1W 4-Band Code (1%) red red yellow brown red red orange brown brown black orange brown blue grey brown brown brown black brown brown yellow violet black brown brown black gold gold 5-Band Code (1%) red red black orange brown red red black red brown brown black black red brown blue grey black black brown brown black black black brown yellow violet black gold brown brown black black silver brown siliconchip.com.au rear of the lid. Once it’s in place, you can apply a bead of the cement around the rim for good measure. Place the assembly aside for a few hours to allow the cement to cure. When the epoxy cement has cured, solder the free ends of the speaker connection wires to the speaker lugs. That done, pass the bared ends of the connecting leads for the remote trigger switches (S1 and S2) through the holes in the lower side of the box and connect them to the terminal block using the screws. Note that the “earth” wires from both switches connect to the centre hole of the terminal block. It’s a good idea to twist them together before pushing them in and tightening the screw. The project is now ready for checkout and adjustment. Checkout & adjustment Before applying power, adjust trimpot VR1 to roughly the middle of its range. That done, connect a 9-12V DC power supply to CON1 and touch the ends of the connection wires for S1 together briefly. You should immediately hear the recorded door sound, lasting almost a second. When it ends, try touching the ends of the wires for S2 together, to produce the second sound recorded on the HK828. LED1 should blink while either sound is being played. You should be able to adjust the Fig.2: the circuit board fits neatly inside a standard UB3-size plastic case and is secured using M3 x 10mm machine screws and nuts – see text. The loudspeaker is secured to the lid using epoxy adhesive. volume of the sounds up or down to the level you want using trimpot VR1. This is the only adjustment to be made, so once you’ve found the right volume setting, the unit can be completed by screwing on the box lid using the four self-tapping screws provided. That’s it! Your Door Sounder is now finished and ready for use. Beam me SC up, Scotty! Looking for real performance? NOT A REPRINT – Completely NEW projects – the result of two years research & development • Learn how engine management systems work • Build projects to control nitrous, fuel injection and turbo Fro m the pu bli sh ers 160 PAGES 23 CHAPTE RS of boost systems • Switch devices on and off on the basis of signal frequency, temperature and voltage Intelligen t turbo timer • Build test instruments to check fuel injector duty cycle, fuel mixture and brake and coolant temperatures • Speedo Corrector, Turbo Timer & Digital Thermometer Projects Mail order prices: Aust. $A22.50 (incl. GST & P&P); Overseas: $A26.00 via airmail. I SBN 095 852 294 9 7809 5 8 5229 4 $19.80 (inc GST) -4 s fuel cont rollers 6 NZ $22.00 (inc TURBO B OOST & nitrou GST) How eng in managemene t works Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. siliconchip.com.au June 2006  97