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SIMPLE PROJECTS FOR MODEL RAILROADS Most model railroad layouts are fairly basic but by spending just a few dollars and a little time with a soldering iron, you can make your layout far more realistic and interesting. These three circuits are easy to build and can be added to virtually any model railroad layout. 1. Train Controller Our first circuit is for a Low-Cost Model Train Controller with simulated inertia - see Fig.1. Many model railroad sets come with a simple rheostat controller but these give poor lowspeed running characteristics. They also give rise to jack rabbit starts and a model that slows or even stalls on curves and gradients. Unlike a rheostat controller, the circuit of Fig.1 behaves as a constant voltage source at any given throttle setting and this gives much improved control at low running speeds. In particular, starting is much smoother and the model no longer stalls or slows when the going gets a little tough. Of course, a pulse power controller gives even better control but is much more expensive than the controller described here. As a bonus, our low-cost controller 26 SILICON CHIP These three low cost projects will enhance the appeal of any model railroad layout. They include a low-cost train controller, a traffic lights simulator & a points controller. By TERRY MOWLES provides simulated inertia and braking. This is just a fancy way of saying that the train adjusts its speed gradually when you vary the throttle and slows gradually when the brakes are applied, just like a real train. A couple of preset pots allow you to adjust the amount of inertia to suit your layout. How it works Fig.1 shows the circuit details. It's basically a beefed-up version of the controller published in the November 1990 issue. The original circuit could supply up to 1.2A whereas this new version can supply up to 3A. This is useful if you want to multiple-head locos, particularly if they have smoke generators, lighting and sound generators. Power is derived from a 3A 12V AC source (eg, via a mains transformer) and this is rectified by diodes D1-D4 to provide about 17V DC. Alternatively, the bridge rectifier can ,be bypassed and the unit operated from a 12-18V DC source. This voltage is then tapped off by throttle control VRl and applied to the base ofQl via Sla, D5, VR2 and a series 5.6kQ resistor. Ql and Q2 form a Darlington output stage and this is forward biased as soon as the voltage on Ql 's base reaches 1.3V. Q2 then conducts and supplies voltage to the track via a 0.22n 5W resistor. Double pole switch B 12-18VAC 05 1N4007 SPEED VR1 5k 0 INERTIA VR2 1k EOc VIEWED FROM BELOW 0 PLASTIC SIDE m BRAKE S1a 0 B A~K ECB 47 + 25VW_ S1b + 4700 25VW- FORWARD S2a 4700 REVERSE BRAKE LEVEL VR3 1k FORWARD S2b TO TRACK REVERSE LOW COST 3A TRAIN CONTROLLER Fig,1: the circuit uses Ql & Q2 to buffer the output of throttle control VRl. Q3 provides overload protection by reducing the drive to Ql when the voltage across the 0.22Q resistor reaches 0.65V. S2 provides forward/reverse switching by swapping the supply polarity to the track. Q3, LED 1 and the 0.22Q resistor provide overload protection. Normally, the voltage across the 0.220 resistor is less than 0.65V and Q3 has no affect on the circuit operation. When a short circuit occurs, the output current shoots up until there is about 0.65V across the 0.220 resistor. Q3 then turns on and reduces the drive to Ql, thus limiting the output current to about 3A. LED 1 indicates that an overload has occurred. VR2 and its associated 4700µF capacitor provide simulated inertia for the throttle. This inertia effect occurs TO TRACK a~ S1 s2[ ~ ~ because it takes t1me for the capacitor to charge or discharge to its new level each time the throttle is varied. D5 prevents the 4700µF capacitor from discharging through VR1 when the throttle setting is reduced. VR3 and the 4700µF capacitor provide the braking inertia. When braking switch Slb is closed, Sla opens and the 4700µF capacitor discharges via the 4700 resistor and VR3. This gradually reduces the voltage on the base of Ql so that the train slows to a stop. When the brake is subsequently released, the train builds up speed to its previous setting (assuming that VR1 is not touched in the meantime). Note that it is not necessary to reFig.2: wire up the Thain Controller as shown in this diagram, The circuit shows the pin connections for transistors Ql, Q2 & Q3. Note that Q2 should be fitted to a large finned heatsink for cooling. duce the throttle to zero before applying the brakes. That's because Sla switches the throttle out of circuit when braking is applied. Building the controller Fig.2 shows the wiring details for the controller. Mount the parts on the TRAIN CONTROLLER PARTS LIST 1 PC board, 106 x 48mm 1 5kO linear potentiometer (VR1) 2 1kO PC-mounting trimpots (VR2,VR3) 2 DPDT miniature toggle switches (S1 ,S2) 1 finned heatsink (see text) 1 TO-3 mounting kit (mica washer plus insulating bushes) Semiconductors 1 BD139 NPN transistor (Q1) 1 2N3055 NPN transistor (Q2) 1 BC337 NPN transistor (Q3) 4 1N5404 silicon diodes (D1-D4) 2 1N4007 silicon diodes (D5,D6) 1 red ~ED (LED 1) Capacitors 1 4700µF 25VW PC electrolytic 1 47µF 25VW PC electrolytic Resistors (0.25W, 5%) 1 5.6kO 1 4700 10.2205W FEBRUARY 1993 27 It's also possible to bolt the transistor directly to the heatsink, provided that you make sure that the heatsink does not touch any other component. That's because the heatsink will now float at the full supply voltage if there is no isolation. 2. Traffic Light Simulator The Train Controller PC board can be hidden under the layout, while the controls can be mounted in a small plastic case to give a walkaround throttle or they can be mounted on the main console. If you intend operating the unit from a DC source, install D1-D4 anyway so that the supply can be connected with either polarity. The 5W resistor should be mounted about 5mm proud of the T03 -....;;;:::.;;;;:;~;:::;::;:;;::::;;:~ DEVICE board, so that the air can circulate beneath it to provide additional coolMICA ing. We mounted the LED directly on ~WASHER the board but it could also be mounted ~ elsewhere (eg, on a control panel) and C connected by flying leads. C> C> HEATSINK C Be sure to install the LED with the correct polarity, otherwise the overload protection circuitry won't work ~ INSULATING ~ BUSHES (its anode lead is the longer of the two). Use medium-duty hook-up wire tfltJ-R<at> for the connections to the power supS~~~EA~ ply, track and switch S2, since these <at> <at>w~m~s leads carry currents up to 3A. The remainder of the wiring (ie, to the ©> LED, Sl and VR1) can be run using <at>NUTS rainbow cable or light-duty hook-up Fig.3: here are the mounting details wire. for Q2. It should be isolated from the Finally, power transistor Q2 must heatsink using a mica washer & be mounted on a large finned heatinsulating bushes. sink, since it dissipates quite a lot of power. Fig.3 shows the mounting dePC board exactly as shown, taking . tails. Note that the transistor is electricare to ensure that all polarised parts · cally isolated from the heatsink using are correctly oriented. In particular, a mica washer and two insulating note that the metal face of the BD139 bushes. Smear all mating surfaces with (Ql) faces towards the 4700µF capaci- heatsink compound before bolting the assembly together. tor. e s~::~:~iF 28 SILICON CHIP Fig.4 shows the circuit for the Thaffic Light Simulator. This was first published in SILICON CHIP in November 1989. It drives green, red and yellow LEDs to accurately simulate traffic light cycles at an intersection. 555 timer IC1 is wired as an astable oscillator and this provides a clock signal for IC2, a 4017 decade counter. IC2 's 0-9 outputs go high in turn on each successive clock signal and drive several sets of OR gates made up by diodes D1-D20. These OR gates then drive transistors Q1-Q6 to control the traffic light LEDs (LEDs 1-12). Note that each transistor drives two LEDs of the same colour, one for each opposing light set. When pin 3, pin 2 or pin 4 of IC2 is high, Ql turns on and lights LEDs 1 & 2 (green) for one set of lights. Q4 will also be turned on during this time TRAFFIC LIGHTS PARTS LIST 1 PC board, 92 x 78mm 9 PC stakes Semiconductors 1 555 timer (IC1) 1 4017 decade counter (IC2) 1 7805 3-terminal regu lator (REG1) 6 BC548 NPN transistors (0106) 4 green LEDs (LED1 ,2, 11, 12) 4 yellow LEDs (LED3,4,9, 10) 4 red LEDs (LED5,6,7,8) 20 1N914 silicon diodes (D1 D20) 1 1N4007 silicon diode (D21 ) Capacitors 1 220µF 25VW PC electrolytic 1 100µF 16VW PC electrolytic 2 10µF 16VW PC electrolytic 1 0.1µF metallised polyester Resistors (0.25W, 5%) 6 100kO 6 4700 1 82kO 1 2200 1 4.7kO 1 1500 100k ~ ~ 16 ~ ~ D4 1N914 1 2 4 7 Vk s ~ IC2 4017 D5 10 4 5 1 6 5 14 82k 7 6 9 IC1 555 11 13 ~ ~ 10 + ~ D17 1N914 16VW+ +9V D21 1N4007 +12V 100 + 2200 16VW+ LED7-8 GREEN LED9·10 YELLOW 1500 ~ B ROC VIEWED FROM BELOW ~ Jt 100k 100k ~ ~ ~ ~ ~ I G0 TRAFFIC LIGHT SIMULATOR Fig.4: the Traffic Light Simulator uses 555 timer IC1 to clock decade counter IC2. This device then drives the traffic light LEDs via transistors Q1-Q6 & a number of OR gates formed by diodes D1-D20. Fig.5 (right) shows how the parts are installed on the PC board. Each output driv~s tw,p LEDs of the same colour, one for each opposing set of lights. HIGH12J (via an OR gate consisting ofD11-D16) and this turns on the two red LEDs for the other set of lights. The other diode OR gates ensure that the remaining LEDs for each set of lights turn on and turn off in the correct sequence as the 4017 counts up. For example, when pin 7 is high, Q2 and Q4 are on and this lights LEDs 3-4 (yellow) and LEDs 7-8 (red) . As with real traffic lights, there is a brief period of time when both sets of lights are red (ie, pin 10 or pin 11 high). Each complete cycle takes about 25 seconds and is then repeated. The timing period can be altered by .changing the timing components in the oscillator (ICl) . Power for the circuit can come from any +12V DC source and this is applied to REGl to derive a regulated +9V rail. Diode D21 protects the circuit against reverse supply polarity. Finally, a lOµF capacitor and 4. 7kn resistor are used FEBRUARY 1993 29 Protect your valuable issues Silicon Chip Binders These beautifully-made binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a distinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. * High quality * Hold up to 14 issues * 80mm internal width * SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A 11 .95 plus $3 p&p each (NZ $6 p&p). Send your order to: Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 979 6503; or ring (02) 979 5644 & quote your credit card number. Use this handy form l ----------Enclosed is my cheque/money order for $._ _ _ or please debit my □ Bankccird □ Visa □ Mastercard Card No : Card Expiry Date _ _/_ _ Signature _ _ _ _ _ _ _ __ Name _ _ _ _ _ _ _ _ __ Address_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ P/code_ __ ., _ _ _ _ _ _ _ _ _ _ _ ,1 30 SILICON CHIP This is the finished Traffic Light Simulator board. Take care with component orientation & note that diode D21 is a 1N4007 type. The remaining diodes are all 1N914 types & are installed with their cathodes towards transistors Q1-Q6. to provide a power-on reset signal for ICZ. This is necessary to ensure that the 4017 starts reliably each time power is applied to the circuit. capacitor's charge is dumped via DZ into one of the two solenoids that are used to control the points (one to open them and one to close them). During Construction Fig.5 shows the PC board parts layout for the traffic light simulator. You can install the parts in any order but take care with component orientation. The outputs that drive the LEDs are all marked on the PC board. Note that each output drives two LEDs of the same colour, one for each opposing set of lights. The LED anodes are all connected together and wired to the +9V output on the PC board. 3. Points Controller The final circuit is the Points Controller - see Fig.6. It can be powered from any 12-15V AC or DC source. Dl half-wave rectifies the incoming voltage in the case of an AC supply, or provides reverse polarity protection in the case of a DC supply. When power is applied, Ql conducts and quickly charges the 2200µF capacitor. At the same time, LED 1 lights to indicate that the circuit is ready. The points can now be opened or closed by pushing one of momentary-contact pushbutton switches (either S1 or S2). As soon as S1 or S2 is pushed, the There is room on the Points Controller PC board for a second 2200µF discharge capacitor, should this prove necessary to operate the solenoids. POINTS CONTROLLER PARTS LIST 1 PC board, 54 x 36mm 1 TIP41 C NPN transistor (01) 3 1N4007 silicon diodes 1 red LED (LED1) 1 2200µF PC electrolytic 1 2.2kQ 0.25W resistor 1 3900 0.25W resistor Why pay $1000's for encyclopedias? If you own a computer with a CD drive, then you can own the 22 vol NEW 1991 Grolier Electronic Encyclopedia for $160. Let the computer do the scanning! LQQK PARENTS SQNy; Computer Requirements either, 1) IBM PC. PS2 or compatible, 512K. MSDOS 3.0, VGA card & Monitor CD ROM Drive OR 2) Apple Macintosh with CD Rom Drive. LQQK PARENTS CD\ROM & SOFTWARE ~ s: ~ II MIXED-UP MOTHER GOOSE* SONY LASER LIBRARY FAMILY. 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PACKAGE CONTENTS Sony internal drive CDU 535 which supports CD Rom mode 1 & 2 & Audio Value $540 (one year warranty) Sony bus interface card (half card value $180) Software - 6 CD's as detailed - Value $998 Microsoft CD - Rom Extensions SPECIAL OFFER - all for IBM (also Mac where shown) ORDER PRICE Chess with sound and animation D $90 Microsofts musical journey (also MAC) D $135 9 Bibles 3000 Sermons, 6 dictionaries D $90 Classic story - music and sound effects D $90 A classic game - now a classic CD D $90 - see above as above plus animated sequences see above - (also MAC) Invaluable Information, 1500 Q & A's - (also MAC) USDA's database, nutrients, calories- analyse foods Games - inc Chessmaster, Bruce Lee, Black Hole Games - inc Loopz, Puzzle Gallery, Robot Tank Tour London, New York, Sydney and 7 others Tour Berlin, Chicago, Rome, and 7 others Multimedia - the best seller plus pictures and sound A living book - childrens' interactive fun A classic game - now a classic CD See above Windows version - see above see above see above 600MB of IBM compatible code, 10,000 programs Nursing literature from Medline 1962-89 Text and Images on horticulture. weeds, etc DTP Program incl, WP, 69 fonts, 1000 clips Consulting Detective - interactive game Interactive Fairytale - adventure game Timelines with sound and animation (also MAC) Clip art, animations, games, digitized music Deluxe version of the bestseller The best seller in•compact format Popular game plus Secret Missions 1 & 2 Popular game plus Ultima V1 see above - (also MAC) D D D D D D D D D D D D D D D D D D D D D D D D D D D D D $410 $690 $160 $135 $90 $70 $70 $135 $135 $159 $90 $90 $159 $159 $90 $90 $90 $190 $90 $135 $90 $90 $90 $90 $135 $135 $90 $90 $90 I'll MICROSOFT • 1M BOOKSHELF 1991 ., · . _- This indispensable collection of reference materials includes the American Heritage Dictionary, Roget's II Electronic Thesaurus, the World Almanac and Book of Facts, Barlett's Familiar Quotations, and more. For added efficiency, all reference volumes interface directly with more popular word processing programs. CDU 535 DRIVE SPECS 5¼" Half-Height Internal 340ms avg. access time 150KB sustained data transfer rate 600KB burst data transfer rate 8KB buffer Output jacks for stereo and head phones r - MAILTH,scouPONroDAv- , I I (Allow 14 days for delivery) I I I I I I .:~.(~:>........... . . I D D I D I I I I I I I I I I II I I I II I PELHAM PTY LTD I enclose cheqoe, money order for$..................... 1 :r~:r:~;~::r::.. Address ............................................................ :........... ............................................... Postcode .................... . Phone ..................................... Fax no ........ ,................ . BANKCARD MASTERCARD VISA Card Number: Expiry date.................................................................... Cardholders Signature ............................... .................. . L 1at Floor, 100 y.,.... Road, Pennant HIiia 2120 Ph (021 HO 8988 Fax (02t 980 n91 See ue II Booth 141, HOME COMPUTER SHOW, Melbourne I I I I II I II I I .J D1 1N4007 12-15V AC OR DC Q1 TIP41C Fig.6 (left): the Points Controller uses the discharge qirrent from a 2200µF capacitor to control the points solenoids. This capacitor is charged via Ql when power is applied. The capacitor discharges & Ql turns off each time one of the pushbutton switches is press_ e d. Fig.7 (below) shows the parts layout on the PC board. ~ J ---------e--o BCE $1 E D2 1N4007 ~ TO POINTS SOLENOIDS ----------e--o + GND 12-15V AC OR DC +V TO 51 AND 52 GND 2200 25VW_ LED1 GNDo-------------t------oGND POINTS CONTROLLER this time, DZ also pulls Ql's base below its emitter and so Ql is turned off. This ensures that the points solenoid only receives a brief current pulse from the charged capacitor and prevents it from burning out if the button is held down for too long. The ZZ00µF capacitor charges via Dl and Ql again as soon as the pushbutton switch is released. D3 protects Ql against any large negative-going spikes that are generated when the solenoid turns on. By the way, you can use this circuit to control as many sets of points as you wish - just wire in additional m,omentary contact pushbutton switches to control their solenoids. Construction Assemble the parts on the PC board as shown in Fig. 7, making sure that Where to buy the kits Kits for these projects are available from T. A. Mowles, PO Box 491, Noarlunga Centre, South Australia, 5168; or from Force Electronics stores in Adelaide, South Australia. The prices are as follows: (1 ). Train Controller (does not include heatsink or TO-3 mounting kit) .. $27.95 (2). Traffic Light Simulator (includes 12 miniature LEDs) ..... .......... ....... $22.95 (3). Points Controller (does not include switches) ..... .. ....... ....... .. ..... ....... $9.95 Payment should be made by cheque or money order. Please add $3.50 for p&p or $5 for 2-5 kits. Note: copyright of the PC board patterns is retained by T. A. Mowles. all polarised parts are correctly oriented. Note that some points solenoids may require more current than can be delivered from a single ZZ00µF capacitor. For this reason, there's space on the board for a second capacitor if required. No heatsink is required for the TIP41C since it only dissipates a few milliwatts. If the LED brightness is insufficient, reduce the value of the series 2.ZkQ current limiting resistor. In some cases, it may be necessary to come down to 1.ZkQ. SC RESISTOR COLOUR CODES No. TRAIN CONTROLLER 0 0 0 0 1 1 1 Value 4-Band Code (5%) 5-Band Code (1%) 5.6kQ 470Q 0.22Q green blue red gold yellow violet brown gold not applicable green blue black brown brown yellow violet black black brown not applicable 100kQ 82kQ 4.7kQ 470Q 220Q 150Q brown black yellow gold grey red orange gold yellow violet red gold yellow violet brown gold red red brown gold brown green brown gold brown black black orange brown grey red black red brown yellow violet black brown brown yellow violet black black brown red red black black brown brown green black black brown 2.2kQ 390Q red red red gold orange white brown gold red red black brown brown orange white black black brown TRAFFIC LIGHTS SIMULATOR 0 0 0 0 0 0 6 1 1 6 1 1 POINTS CONTROLLER 0 0 32 1 1 SILICON CHIP