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INFRARED REMOTE CONTROL FOR MODEL RAILROADS, PT.2 In this second article on our new remote control for model railroads, we present the circuitry for the remote control receiver. This mates up to the pulse power board described last month. It also providesJatched and momentary outputs which can be used to control signalling, points and lighting on a model railway layout. The receiver circuit comprises eight ICs plus quite a few transistors and diodes, as shown in Fig.7. IC5 and IC6 are . the infrared remote control devices, while IC7, IC8, IC9, IC10a and ICl la provide the control signals for the pulse power circuit. Finally, IC10b, ICllb and IC12 are used for the various latched outputs. IC5 , a Plessey SL486 infrared preamplifier IC, is specifically designed for processing infrared control signals. This device features a differential photodiode input to reduce noise pickup and an automatic gain control circuit for improved operation in noisy By LEO SIMPSON & JOHN CLARKE" 76 SILICON CHIP ·' environments. It also incorporates two gyrator circuits and these allow the device to receive signals in high ambient lighting conditions, such as from incandescent lamps. The incoming IR signals from the remote control transmitter are picked up by photodiode IRDl which is connected across the differential inputs of IC5. The received pulses are then amplified and filtered before they appear at pin 9. Capacitors connected to pins 2, 3, 5, 6 and 15 ofICl roll off the frequency response of the gyrator and gain stages below about 2kHz. This effectively filters out any 100Hz signals produced by mains-powered lamps. Automatic gain control is provided by an internal peak detector which measures the output signal appearing at pin 9. A O. lµF capacitor at pin 8 filters the output of the peak detector and the resulting signal is used to control the gain of the first three amplifier stages. Signal decoding The signal from pin 9 of IC5 is directly connected to pin 1 of IC6, the decoder IC. This provides five BCD (A, B, C, D & E) outputs which can be either momentary or latched, depending on whether pin 5 is high or low. We have selected momentary operation by tying pin 5 high. In addition to the five BCD outputs, IC6 provides a Data-bar signal which goes low whenever a valid code is present on the A, B, C, D & E outputs. This signal is used to drive the ACKnowledge LED (LED 6) via a 3300 resistor. This LED therefore indicates whenever the remote control circuitry is receiving a valid signal from the transmitter. Pins 3 and 4 are the A and B rate inputs and must be connected to match the transmitter rate input connections. When the links to these inputs are left open, internal resistors tie them high (ie, to +12V). Three of the BCD outputs from IC6 are connected to IC7, a 4051 3-8 decoder (also known as an analog multi- plexer). Depending on the BCD code presented to its inputs, IC7 pulls one of its eight outputs (pins 1, 2, 4, 5, 12, 13, 14 & 15) high. Actually, what really happens is that one of the eight pins is connected to the common pin (3) which is tied to +12V via a 2.ZkQ resistor. The A, B and C inputs of IC7 are only decoded when the INHibit input (pin 6) is low. This input is connected to the Data-bar output of IC5 via a lOkQ resistor so that decoding is done only when valid data (low output) is present on the A, B and C inputs. Note that pin 6 of IC7 is also controlled by the D and E outputs of ICZ via diodes D15 and D16. Thus, when either the D or E output goes high, it inhibits IC7 and prevents any of its outputs from going high. Logic level conversion IC5 and IC6 operate between the +12V and +7V supply rails, while IC7 operates from +12V, +7V and 0V. The reason for this messy arrangement is because IC6 requires a 5V supply while the rest of the circuit needs to be compatible with the pulse power PC board which operates at 12V. Thus, IC7 not only decodes the signals from IC6 but also provides logic level conversion so that its output signals swing between 0V and +12V. The +12V supply for the circuit is · obtained from the +12V regulator on the pulse power PC board, while the +7V supply is derived from a separate -5V 7905 2-terminal regulator. This may seem a little unusual but the 7905 effectively operates as a current sink and subtracts its 5V from the 12V rail to give the +7V rail. Auxiliary outputs The five auxiliary control outputs are derived from the "5", "6" and "7" outputs of IC7 and the D and E outputs of IC6. The "5", "6" and "7" outputs of IC7 connect to the clock inputs of D-flipflops IC12a, ICl0b & ICl lb respectively. These are each Shown below is the completed pulse pow.er board, together with the handheld controller that's used to test it. These two items are identical to the Railpower project published in the April 1988 issue of SILICON CHIP, which means that you can easily convert the original project to remote control. MAY1992 77 "O ~ C") % Q n (/) C:: ~ I . 0 ~ v 1 CASE - • l 8 .1. O· - 6 a, 16VW .01s _ 40f!Jw<~~ -,- "':r DISABLE LEVEL· VR310k ,ra 9 100pF '" . GNO · IN. l T l A .1. 10M¾ .,. ' MOM' TiJT=F- + METER SET VR!ii2.2k ~~ (L, 1~\ "" 8 " , 9 ·--, I - INFRAREO RECEIVER BOARD RAILPOWER · 11 .,. 16 -,f -i/:,17 -1il!i 1 L R Js I ~~ ~ I I c .l I I "' . 100k~ I • I :3: ~ I 0.1 I .,. . t • C·~'" .,. .,. • I " _.,, .... '· t IC10b - . - -r---..::~.,___:!;i~---100k . 11• t J L r-c:_.,_____ "i ,--·· -1 I 0.1 r--+-- 1 l - 4 7 6 n sl 5 +12V I ~ ::1w 3' e !:i 14 1s 12 013 a: 1a: 2.._ 30 4w 7 IC 4051 ' COM '" II I MOMENTARY t='.f-· 100k 0.1 1- ~ +12V· ·"' OH 1N4002 .,_""'°''Nr-....-OUTPUTl1 15 016 r--:r+H-4----_J E ,~..a...l....JD15 2x1N4148 16 .,.7 a '•• 11 A 10 B C,t1"'"3------~-Jc 8 12 A 11· DISCHARGE ECB """ ACKNOWLEOGE ,t-'----4--¥,~---.!J ' 1N4002 204 6.8V ""'~" 400mW PLASTIC SIDE·1 .,. CLR 2 0.11 IC6 MV601 ,__ _ _ ___!!!U .,. r------~--41--J +12V ' K~ BPW50 "" LK1 1 OPEN=1 CLOSED=O T 6.BV 400mW 00pF 1 l 22 -+ 16VWT +7V <at>~"'-"""-"""'"~'"--'"~' 8.2k OUT .. 00, . ••• I 7905 r,.;,..-_. _.,. ___J ~ ~ 5 I 4 = ml 16VW SL486 3 1· FORWARD/REVERSEh E C VIEWED FROM BELOW OV +12V + 1 8P104 J~ ·" 10; • 16Vwr· >. L ~ i. ~ • ..j. .,. ,.;;;, 'q LEDS , .. . '"' ' +12V !~k l1N4002 +12V ' 019 ,020 1N4002 rt· . rt; ,moo, 021 ·'" ◄ Fig. 7 (left): the receiver board decodes the signals from the infrared transmitter. IC5 (preamplifier) & IC6 (decoder) are the infrared remote control devices; while IC7, IC8, IC9, IC10a & IClla provide the control signals for the pulse power circuit. IC10b, ICllb & IC12 are used to provide latched outputs for signalling, points switching & lighting. OV +12V BUZZER + connected with the D input tied to the Q-bar output so that each time their clock input goes high, the Q output changes state, from a low to a high or from a high to a low. This provides the latched output facility so that the first press of a button on the transmitter latches the relevant output on and the next press latches it off. The Reset inputs of these flipflops are all tied to an RC netw ork consisting of a O. lµF capacitor and lOOkQ resistor. This provides a power-on reset facility. At power-on, the O. lµF capacitor is discharged and so the reset line is momentarily held high until the voltage drops to OV via the lOOkQ resistor. This resets each flipflop so that its Q output is low. The Q outputs of IC12a, IClOb and ICl 1b are connected to transistors Q13, Q12 and Q11 to provide the latched outputs. Alternatively, the flipflops can be bypassed, via a link option, for momentary operation. Each of the three transistors can drive a 12V relay, connected between the collector output and the+ 12V supply. Each transistor has an associated diode to provide protection against any spike voltages that may be generated when a relay is switched off. Also associated with each transistor is a LED (LEDs 5, 6 & 7) which is lit when the output is on. The D and E outputs of IC6 drive transistors QlO and Q9, each via a 6.8V zener diode (ZD5 and ZD4) and a 2.ZkQ resistor. These provide momentary outputs only and, as with the other three outputs, have LEDs (LED4 and LED3) to indicate when they are on. The 6.8V zener diodes are used because the D and E outputs ofIC6 are at +7V when off (low) or +12V when on (high). When the outputs are at +7V, the zener diodes prevent the transistors from turning on. Note that Q9 and QlO are high gain Darlington tran- LE02 vdf I Fig.8: this is the parts placement diagram for the pulse power PC board. Note that IC2 is oriented differently to the other !Cs & take care to ensure th~t the two heatsinks used for transistors Q1-Q4 do not touch each other. Tnmpots VRl & VR2 set the maximum and minimum track voltages & must be adjusted as described in the text. sistors which are needed due to the limited base drive available from the D and E outputs of IC6. Train control The remaining circuitry on the receiver board is used to provide the various throttle functions via the pulse power board. You will need to refer to the circuit diagram of the pulse power board published last month to be able to fully understand the circuit description to follow. There are six connections from the receiver board to the pulse power board. Terminals 1 and 2 provide connections for the minimum and maximum speed setting voltages (from VRl, VRZ , ICla & IClb on the pulse power board). Terminal 3 is the speed control voltage (fed to pin 3, IClc on the pulse power board), while terminals 4, 5 and 6 provide the OV connection and the forward/reverse control. Each of the terminal 1, 2 and 3 points on the receiver board feature input protection for the CMOS circuitry. This takes the form of a 12n series resistor and 12V zener diode to ground (OV). The "O" and "1" outputs of IC7 (pins 13 & 14) correspond to the "faster" and "slower" buttons on the remote control transmitter. They con- nect to the control inputs of CMOS analog switches IC8a and IC8b. When pin 13 ofIC7 goes high (corresponding to the "faster" button being pressed), switch IC8a closes and the 2.ZµF capacitor at pin 3 of IC9a is charged via a 1OMQ resistor connected to the +12V rail. When pin 14 of IC7 goes high (when the "slower" button is pressed), switch IC8b closes and discharges the 2.ZµF capacitor via the lOMQ resistor connected to OV. The 2.ZµF capacitor can charge no higher than the voltage at Terminal 2 and can discharge no lower than Terminal 1. This is achieved by clamping diodes DlO and Dll and the associated resistive voltage divider between Terminals 1 and 2. The reason for using this fairly complicated capacitor charging, discharging and clamping arrangement is to give more linear charging and discharging and thus a better throttle response from the transmitter buttons. Sample and hold The voltage across the 2.ZµF capacitor is buffered by FET-input op amp IC9a which acts as a sample and hold circuit. This is desirable because the capacitor voltage is the throttle setting; you don't want it changing after it has been set. Since the op amp MAY 1992 79 - ' J f vO • Ov o o o _, V · OO c, OOOo VR5 000 following 4 7µF capacitor on the pulse power board will take several minutes to charge to the throttle setting, thus simulating the inertia of a real train. Conversely, if VR4 is set for minimum resistance, there will no inertia, which might be desired for shunting manoeuvres. Braking Fig.9: this is the wiring diagram for the temporary handheld controller. The numbers on the leads correspond to the numbers on the terminal block at the top of Fig.8. VR4 and VR5 set the running & braking inertia. FROM MAIN BOARD IC10a, IC8d and VR5 control the braking. IC10a is a D-flipflop which is normally set with its Q output (pin 1) low and its Q-bar output (pin 2) high. The high on pin 2 closes switch IC8c for the normal run mode (ie, normal running, brake not applied). When the stop output (pin 15) of IC7 goes high, flipflop IC10a changes state. Thus, pin 2 of IC10a goes low, causing analog switch IC8d to open. , At the same time, pin 1 of IC10a goes high and closes analog switch IC8d to discharge the 47µF capacitor connected to Terminal 3 of the pulse power board via trimpot VR5. This is the braking mode. The degree of braking is set by adjusting VR5. Hence, pushing the Stop button on the transmitter will cause the braking circuit to activate and it then stays that way until the Faster button is depressed (a momentary press is all that is required). When this happens, the "Faster" output of IC7, pin 13, goes high and pulls reset pin 4 of IC10a high via diode Dl4. This resets IC10a's Q output to low and the Q-bar output high. Switch IC8d now opens and switch IC8c closes to revert to normal running. Forward/Reverse This view shows how everything fits together inside the hand-held control unit that's used to test the pulse power board. A 6-way telephone cable makes a handy connecting lead. dr'aws an extremely low current (typically 50 picoamps), the rate at which the capacitor discharges will be almost solely due to its own leakage current. In practice, a typical 2.2µF tantalum capacitor should hold a voltage across it for five minutes or more before any noticeable reduction occurs. The output of op amp IC9a is at the 80 SILICON CHIP same voltage as the capacitor and is used to drive the speed setting meter via trimpot VR6. IC9a also drives inertia pot VR4. Normally, the following analog switch, IC8c, is closed and the run inertia pot connects to Terminal 3 of the pulse power board. This input has a 47µF capacitor which is charged via VR4 to set the train speed. If VR4 is set for high resistance, the Forward/reverse control is provided with flipflop ICl la. This is initially set at power-on with its Q output (pin 1) high and th~ Q-bar output (pin 2) low. These outputs are connected to Terminals 5 and 6 and thence to the pulse power board. Thus, when power is first applied, the circuit is set in the forward mode. When the Reverse output - pin 1 of IC7 - goes high, it pulls pin 4 of ICl la high to reset it. This causes the Q output to go low and the Q-bar output to go high. This is the reverse mode. Forward/reverse lockout However, there is more to the forward/reverse control than this. IC9b is an op amp connected as a comparator. It compares the voltage at Termi- nal 3 with the voltage set by VR3. In practice, VR3 is adjusted so that the output ofIC9b goes low only when the voltage at Terminal 3 is so low that the train is either running very slowly or has completely stopped. If the voltage at Terminal 3 is higher than the setting ofVR3, IC9b's output will be high; this is the normal condition while the train is running. The high output from IC9b turns on transistor Q14 and thereby pulls both the set and reset of IC11a low via diodes D12 and D13. This prevents ICl la from changing state and so prevents a change in direction; ie, gives forward/reverse lockout unless the loco speed is zero or very low. This condition causes the For/Rev Off indicator, LED 9, to light. If the For/Rev Off indicator is alight, you cannot change the direction of the loco. Construction We now come to the construction procedure for the pulse power controller. It is housed in a standard plastic instrument case and has two PC boards, as already mentioned. The power transformer and the receiver board are mounted on the base of the case, while the pulse power board is mounted on the lid. We will first describe the assembly of the pulse power board and show you how to get it going as a selfcontained train controller. After that, we will tackle the construction of the transmitter and receiver and marry them to the pulse power board. Fig.8 shows how the parts are mounted on the pulse power board. The 6-way connector is for the connections to the receiver board (Terminals 1-6), while the 16-way connector (actually two 8-way units) is for the rest of the connections. Assembly of the board can start with the wire links, small diodes and the resistors. When these have been installed, you can concentrate on mounting the four output transistors, the 3terminal regulator and their associated h eatsinks. Three heatsinks are required. Ql and Q3 are mounted on one heatsink while Q2 and Q4 are mounted on another. We made ours from 0.8mm aluminium (equivalent to 22 gauge), although the thickness is not important. For each two-transistor heatsink, we RESISTOR COLOUR CODES Value 4-Band Code (1%) 5-Band Code (1%) 10MQ brown black blue brown green blue yellow brown red red yellow brown brown red yellow brown brown black black green brown green blue black orange brown red red black orange brown 560kn 220kQ 120kQ 100kQ 47kQ 27kQ 22kn 15kQ 10kQ 8.2kQ 5.6kQ 4.7kQ 2.2kQ 1kO 8200 3300 1000 47Q brown black yellow brown yellow violet orange brown brown red black orange brown brown black black orange brown yellow violet black red brown red violet orange brown red red orange brown brown green orange brown brown black orange brown grey red red brown red violet black red brown red red black red brown brown green black red brown brown black black red gold grey red black brown brown green blue red brown yellow violet red brown red red red brown brown black red brown grey red brown brown orange orange brown brown green blue black brown brown yellow violet black brown brown brown black brown brown yellow violet black brown 120 2.20 brown red black brown red red gold brown used a piece of aluminium 30mm wide and 55mm long, with a rightangle bend 9mm from one end, which becomes the foot. Four 3mm holes need to be drilled in each heatsink, to take the two mounting screws for the foot and the mounting screw for each transistor. For the 3-terminal regulator heatsink, we used a piece of aluminium CAPACITOR CODES Value IEC Code EIA Code 0.1µF 100n 104 0.022µF 0.015µF 0.01µF 0.0047µF 22n 15n 10n 223 153 103 4n7 n10 472 101 100pF TRIMPOT CODES Value 220kO 100kQ 10kO 2.2kQ EIACode 224 . 104 103 222 red red black brown brown brown black black brown brown grey red black black brown orange orange black black brown brown black black black brown yellow violet black gol~ brown brown red black gold brown red red black silver brown 20mm wide by 45mm long, with a rightangle bend 9mm from one end. Three 3mm holes need to be drilled in it, two for mounting screws and one to secure the regulator. The three heatsinks should be secured to the PC board before the transistors and regulators are soldered into place. Note that the two transistor heatsinks must not touch each other otherwise they will short out the DC supply. Attach the regulator and the power transistors to their respective h eatsinks and then you can solder their leads to the board. Note that mica washers are not necessary for the transistors or for the regulator. Once the transistors and regulator are in place, the rest of the components can be mounted on the PC board. We suggesrthat you solder in the small transistors first , then the two trimpots, the 5W wirewound resistor, the four ICs, the four rectifier diodes and the capacitors. Leave the connector strips till last, otherwise they tend to get in the way when you are soldering other components. Note that ICl and ICZ, the two LM324 op amps, are oriented differMAY 1992 81 PARTS LIST FOR IR MODEL TRAIN CONTROLLER Case & hardware 1 plastic instrument case, 260 x 190 X 80 1 aluminium front panel 1 Dynamark front panel label, 250 x 75mm 1 M2165 60VA transformer 1 piece of 1.5mm gauge aluminium, 120 x 165mm 1 piece of 0.6mm gauge aluminium, 80 x 60mm 1 MU45 1mA meter 1 meter scale, 51 x 41 mm 9 5mm LED bezels 1 16mm nylon bushing 1 1MQ linear pot (VR4) 1 15mm diameter knob 1 9.5mm nylon cable clamp 1 3-way mains terminal block 1 cordgrip grommet for mains cord 1 panel mount 3AG fuse holder 1 1A 3AG fuse 2 solder lugs 2 panel mount banana sockets 1 12V buzzer 6 4BA 9mm Nylon screws plus nuts 4 6mm standoffs Wire & cable 1 mains cord with moulded 3-pin plug 1m 5-way rainbow cable 400mm 4-way rainbow cable 400mm brown medium duty hookup wire 400mm blue medium duty hookup wire 150mm blue mains rated wire 400mm brown mains rated wire 200mm green/yellow mains (earth) wire 200mm red light duty hookup wire 200mm black light duty hookup wire 200mm green light duty hookup wire 200mm red medium duty hookup wire 200mm yellow medium duty hookup wire 200mm blue medium duty hookup wire Miscellaneous Tinned copper wire , solder, 82 SILICON CHIP screws, nuts, self tapping screws, heatshrink insulating tubing, etc. Pulse power board 1 PC board, code SC91488, 117 x 125mm 2 8-way PC board mount screw connectors 1 6-way PC board mount screw connector 2 100kQ miniature vertical trim pots (VR1, VR2) Semiconductors 2 LM324 quad op amps (IC1, IC2) 1 4093 quad Schmitt NAND gate (IC3) 1 4049 hex inverter buffer (IC4) 2 BD650 PNP Darlington transistors (01 , 02) 2 BD649 NPN Darlington transistors (03, 04) 3 BC547 NPN transistors (05, 06, 08) 1 BC558 PNP transistors (07) 1 7812 12V 3-terminal regulator 5 1N914, 1N4148 signal diodes (D1-D5) 4 1N5404 3A diodes (D6-D9) 1 5mm bicolour LED (LED1) 1 5mm red LED (LED2) Capacitors 2 2200µF 25VW PC electrolytic 1 47µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 1 4.7µF 16VW PC electrolytic 1 2.2µF 25VW PC electrolytic 1 2.2µF 16VW PC electrolytic 2 0.1 µF MKT polyester or greencap 1 0.01 µF MKT polyester or greencap Resistors (0.25W or 0.5W, 1 560kQ 1 220kQ 2 120kQ 5 100kQ 1 27kQ6 1 22kQ1 2 15kQ1 1%, 7mm body) 5 10kQ 1 8.2kQ 2 5.6kQ 6 2.2kQ 1kQ 100Q 0.1Q 5W Transmitter board 1 plastic case, 68 x 130 x 43mm 1 PC board, code SC15204922, 88 X 57 1 front panel label, 63 x 125mm 4 black PC board mount momentary switches 4 white PC board mount momentary switches 1 grey PC board mount momentary switch 1 red PC board mount momentary switch 1 216 9V battery 1 216 9V battery clip 4 6mm standoffs 4 2mm x 20mm countersunk screws 12 2mm nuts 4 2mm washers 1 160mm-length 0.8mm tinned copper wire 1 CSB615A 615kHz Murata ceramic resonator (X1) Semiconductors 1 MV500 Plessey remote control transmitter (IC1) 1 BC338 NPN transistor (01) 1 B0140 PNP transistor (Q2) 2 COY89A, LD271 infrared LEDs (LED1, LED2) Capacitors 1 220µF 16VW PC electrolyfic 2 100pF ceramic Resistors (0.25W or 0.5W, 1%, 7mm body) 1 10kQ 1 100Q 1 1kQ 1 2.2Q 1 820Q lnfrared receiver board 1 PC board, code SC15204921, 140x98mm 1 CSB615A 615kHz Murata ceramic resonator 1 220kQ miniature horizontal trimpot (VR5) 1 10kQ miniature horizontal trimpot (VR3) 1 2.2kQ miniature horizontal trimpot (VR6) Semiconductors 1 SL486 Plessey infrared receiver amplifier (IC5) 1 MV601 Plessey remote control receiver (IC6) 1 4051 8-channel analog mutiplexer (IC?) 1 4066 quad analog switch (IC8) 1 LF351, TL072 dual FET input op amp (IC9) 3 4013 dual D flipflops (IC10,IC11,IC12) 2 BO681 NPN Darlington transistors (09, 010) 4 BC338 NPN transistors (011014) 1 BP104, BPW50 infrared detector diode (IRD1) 7 1N4148, 1N914 signal diodes (D1 0-D17) 5 1 N4002 1A rectifier diodes (D18-D22) 3 12V 400mW zener diodes (ZD1-ZD3) 2 6.8V 400mW zener diodes (ZD4-ZD5) 1 7905 5V negative regulator 7 5mm red LEDs (LED3-LED9) 00 00 "f ,... I en Capacitors 1 68µF 16VW PC electrolytic 1 22µF 16VW PC electrolytic 3 10µF 16VW PC electrolytic 1 6.8µF 16VW PC electrolytic 1 2.2µF tantalum electrolytic 6 0.1 µF MKT po lyester 1 .022µF MKT polyester 1 .015µF MKT polyester 1 .0047µF MKT polyester 2 100pF ceramic Resistors (0.25W or 0.5W, 2 10Mn 5% 11 100kQ 1 47kQ 410kn 1 8.2kQ 1 4.7kn 1%, 7mm body) 3 2.2kQ 10 1kQ 1 3300 1 47Q 3 12Q Parts for hand controller (for testing pulse power board) 1 plastic case, 83 x 54 x 28mm 1 1 0kQ linear pot. (VR3) 1 1 MQ trimpot (VR4) 1 220kQ trimpot (VR5) 2 SPOT togg le switches (S1 ,S2) 1 piece of Veroboard (50 x 20mm) 1 6-way cable (to connect to pulse power board) u en ~ Fig.10: compare your etched PC board against this full-size artwork & correct any defects before mounting any of the parts. ently on the board (ie, they point in different directions). Testing Instead of now proceeding to assemble the infrared transmitter and receiver, we suggest that the pulse power board be assembled into the case, along with the power transformer, some of the LEDs and so on. We will assume that you have purchased the full kit so there will be no need to do any metalwork, although you may have to drill holes in the plastic instrument case - see Fig.11. In effect, you will initially be wiring up the complete project minus the receiver board. We will then show you how to wire up a simple hand control (the same as published in our April 1988 issue) so that you can put the pulse power board through its paces. The 60VA transformer is mounted on a metal plate in the lefthand side of the case. The metal plate (we used 20-gauge aluminium sheet) is then secured to the case using four of the integral plastic pillars in the base. A 3-way insulated terminal block is required to terminate the mains wiring to the power switch and transformer. The mains Earth (green/yellow) wire is terminated to a solder lug which is attached to the transformer mounting plate. The mains wires to the power switch and fuseholder should be fitted with heatshrink sleeving to prevent any accidental contact. When fitting the mains cord, make sure it is anchored to the rear panel of the case using a cordgrip grommet. Mount the pulse power board on the lid of the case with four screws and nuts. We used nylon screws for this job since they are safer and the screw heads are less noticeable on the lid. Lay the lid, with the pulse power board fitted to it, to the right of the base and run the necessary wiring. The two transformer secondary windMAY 1992 83 Fig.11: this diagram is provided to enable you to initially install the pulse power board, power transformer & mains wiring. The pulse power board can then be tested with a hand-held throttle (see Fig.9). The installation of the receiver PC board & the rest of the wiring will be described next month. PULSE POWER PCB ON l:ASE LIO 11 ALUMIN IUM FRONT PA~NEL LED7 A - PLASTIC REAR PANEL 6 5 - )A 5 pf-A TRACK OUiPUT TERMINALS INFRAREO RECEIVER PCB p=ol LEDB A I LED9 ~ K L~ f~ 4-~A 1~1/1 K 2 LED1 K I OUTPUTS TO RELAYS ALUMINIUM BASE PANEL F1 84 SILICON CHIP LEO4 . . LE~) -e ~ 1.,,.,.. A. ~ ~~ A GROMMETG e 3 ~===================~s1 1 6 , r~ . The run & stop inertia adjustment pots (VR4 & VR5) in the hand-held controller are mounted on a small piece of Veroboard. Note: these pots are optional for testing purposes & could be replaced by wire links. ings are connected in parallel (0V to 0V and 12V to 12V) before being connected to the relevant points on the connector strip. You can also wire in the overload buzzer and the output (track) leads which connect to binding post terminals on the rear panel. The LEDs can be connected directly to the connector strip at this stage, leaving the permanent wiring till later. Handheld control To test the pulse power board, you will need a handheld control and we have shown one wired up on Veroboard in Fig.9. It is wired up to Terminals 1-6 on the pulse power board. Switch Sl functions as a Run/Stop switch while switch S2 provides forward and reverse. VR3 becomes the main speed control, VR4 the inertia control, and VR5 the braking control. However, don't wire in the control until you have made the following voltage checks. Powering up Having completed the wiring, check your work carefully and then apply power. A number of voltage checks should now be made. To make these easier, orient the pulse power board in the same direction as the diagram of Fig.8 and have last month 's issue open at the circuit diagram on page 70. That way, it will be easier to find your way around the board. Switch your multimeter to the 20V DC range and check that + 17V is present at the IN terminal of the 3terminal regulator (you can pick it up at the end of the adjacent 2.2kQ resistor) and at the emitters of Ql and Q2. Depending on the incoming mains voltage, this measurement is likely to be anywhere between+ 17V and +21 V, or even a little more. TABLE 1 IC Pins Voltage IC1 1, 2, 3 +1.2V IC1 5,6, 7 +4.8V (triang le waveform at pin 9, square wave at pin 7 IC1 8, 9, 10 Same as wiper of VR1 IC1 12, 13, 12 Same as wiper of VR2 IC2 1 +11V IC2 2 ov IC2 3 +0.6V IC2 5 10.1V IC2 6 +9.8V IC2 7 +12V IC2 8,9, 10 Close to 0V IC2 12 +1 .8V IC2 13 Same as pin 6, IC1 IC2 14 ov Now check for +12V at the output of the 3-terminal regulator and on each of the supply pins of the ICs: pin 4 of ICl and IC2, pin 1 ofIC4, and pin 14 of IC3. Again, the actual voltage will vary between +ll.4V and +12.6V, depending on the actual 7 812 (or LM340T-12) used. The voltages around !Cl and IC2, as shown in Table 1, should now be checked with the handheld throttle disconnected. These voltages are "ballpark" figures only but should be a good guide to see that things are working. Now you can wire in the handheld control and check that the voltages at pins 3 and 4 swap from high to low or vice versa when the forward/reverse switch is operated. Check that the voltages at pins 6, 7, 9, 10, 11, 12, 14 & 15 also change state when the forward/reverse switch is operated. Now connect your multimeter across the output terminals of the controller and wind the throttle control up to maximum. Adjust VRl on the pulse power board so that the voltage is 12V (or whatever is the maximum recommended operating voltage for your locos). Now rotate the throttle to the minimum and adjust VR2 for an output of 1.5V (you will want to "fine tune" this minimum setting once you start operating trains). Now note that the polarity of the output voltage changes when you operate the forward/reverse switch and that the colour of the track LED changes (from red to orange or vice versa). Now wind the throttle to about the half-way mark and briefly short the output terminals. The overload LED should light and the buzzer should sound. You can also listen to the operation of the controller by connecting a loudspeaker to the output terminals via a l00Q resistor. (Don't connect it directly otherwise you'll probably blow the loudspeaker). At low throttle settings, the loudspeaker will have a thin, reedy sound. At higher settings, the sound will be louder but more mellow. With all those checks made, you can now run trains if you like. After all, you probably want a break from soldering at this stage. Next month, we shall complete the project by presenting the assembly details of the infrared transmitter and receiver. SC MAY 1992 85