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INFRARED REMOTE CONTROL FOR MODEL RAILROADS, PT.3 In this final article on our new remote control for model railroads, we describe the assembly of the transmitter and receiver boards and the connection of the receiver board to the pulse power board. The remote control transmitter is built into a standard plastic case measuring 68 x 130 x 43mm. This is fitted with a Dynamark adhesive label and the PC board inside measures 88 x 57mm and is coded SC15204922. Before mounting any parts on the transmitter PC board, it should be used as a template to mark out the hole positions for the switches on the front panel. In the centre of each of the nine switch locations is a 1mm hole which marks the drilling centre for each switch. Place the PC board on the underside of the lid and with the copper side facing out (ie, as it will be when finally mounted on the lid). Position it so that the end with the By LEO SIMPSON & JOHN CLARKE 24 SILICON CHIP LEDs just clears integral lid pillars. Align the PC board so that it is centred on the case lid and mark and drill out the corner mounting holes through the case lid. Countersink the holes on the outside of the case lid to suit the 2mm countersunk screws. Now secure the countersunk screws to the lid with a nut and temporarily mount the PC board so that the centre hole positions for each switch location can be drilled out with a 1mm drill. This done, remove the PC board and drill the switch holes out to 3mm. The Dynamark adhesive label can now be affixed to the front panel. Before you do that however, you must install and secure each of the four countersunk screws with a nut and lockwasher. Once the label has been affixed, the switch holes can be reamed out to a diameter of 10mm to Transmitter board assembly board. We used white buttons for the faster, forward and 1 and 2 auxiliary switches; black for the reverse and 3, 4 and 5 auxiliary switches; grey for the slower switch; and red for the stop switch. Now mount the IR LEDs. These are mounted with their leads at full length - don't cut them. They are bent over at 90° close to the top of the PC board. Be careful with the orientation of these LEDs (the anode lead is the longer of the two - see Fig.6). Two 5mm holes need to be drilled at one end of the case, to allow the infrared LEDs to protrude. Finally, the battery snap connector can be soldered with the red lead connecting to the positive (+) point and the black lead to the(-) point. The PC board is secured to the lid using the countersunk screws and is mounted on spacers which comprise the nut and lockwasher already in place, a 6mm spacer and a further nut. A final nut on each screw secures the PC board in place. To make the transmitter case easier to handle, we cut it down by 12mm so that its overall depth, with the lid on, is 30mm. To do a neat job of this you need access to a docking saw, radial arm saw or bandsaw. You could do it by hand with a hacksaw and files but it would be a tedious task. You will also need to fashion a bat- You can start the assembly of the transmitter PC board by installing the resistors and the eight wire links. The links can be straight lengths of 0.6mm tinned copper wire or made from the pigtails left over after the resistors have been installed. We suggest that you use the LK3 and LK4 linking options (for transmitter coding), as shown on the PC board component diagram of Fig, 12. Now insert the transistors and capacitors, taking due care with their orientation. To ensure adequate clearance below the front panel, transistor Ql is mounted close to the PC board while transistor QZ is mounted and its leads bent so that it lies over the top of the z.zn resistor. Similarly, the 220µF capacitor is mounted on its side, flat against the board. The ceramic resonator Xl can be mounted now. The 10 pushbutton switches are mounted hcifd against the PC board with the flat side of each switch facing towards the IR LED end of the PC The transmitter PC board is used as a template for marking out the front panel holes before any of the parts are installed. Bend the leads of the infrared LEDs as shown so that they protrude through matching holes in the end of the case. Fig.12: parts layout for the transmitter PC board. Install each switch with its flat side facing towards the IR LEDs & note the mounting arrangement for the 220µF capacitor. provide clearance for the switch tops. By the way, don't attempt to drill the holes out to this diameter. The chances are that the holes will be more triangular than round and you may very well rip the thin metal of the label. tery holder using some scrap aluminium. When complete, you can clip the battery snap to the battery and screw on the case lid. Receiver assembly The receiver PC board is coded SC15204921 and measures 140 x 98mm. You can begin the assembly of the receiver board by inserting all the PC stakes and the links. Note that links LK1 and LKZ are for coding the The PC board is stood off the lid of the case using two nuts, a lockwasher & a 6mm spacer. A final nut on each screw then holds the board in place. JUNE 1992 25 TO PULSE POWER PCB +12V +12V 6 5 ov 4 3 2, 1 • • • • • • • • Fig.14: outputs 3, 4 & 5 are set up for latched or momentary operation by installing solder bridges on the PC board. You can make them all latched, all momentary or choose a mixture of both. A and B rate inputs of ICZ. They must match the coding used in the transmitter. There is one particularly long link on the board, running from one side of the board to pins 1 & 2 of IC9. It should preferably be insulated. You can either use a length of insulated hookup wire or 0.6mm tinned copper wire fitted with plastic tubing. Next, the ICs can be inserted, taking care with their orientation. The resistors, diodes and zener diodes are mounted next and then the capacitors, transistors, resonator Xl and the trimpots. Finally, LED 6, LED 7 and infrared diode IRDl can be mounted. Be careful with their orientation; the longer lead is the anode lead. These three devices should be mounted with their leads at ffitt.Y~ y --- L 0-, -0,.-::::~.,~~ o o-. Fig.15: here is the full-size etching pattern for the receiver PC board. 26 . SILICON CHIP maximum length. This will allow the LEDs to be bent and clipped into the front panel bezels and the infrared diode to mount flush with its front panel opening. Momentary/latched outputs To avoid more work later on, you should now decide whether you want momentary or latched operation of . the auxiliary outputs 3, 4 and 5 (or a mixture of both). These linking options are done on the track side of the PC board by making solder bridges as shown on Fig.14. Do not solder bridge both the momentary and latched connections on the one output - if you do, it won't work. Case assembly details Last month, we described the temporary installation of the pulse power board and a handheld controller intended to let you check the operation. Now we come to the point when the receiver PC board is mounted in the case and married up to the pulse power board. Below: the receiver PC board is secured to four integral pillars on the base of the case using self-tapping screws. Fig.11 (published last month) shows how this board is then wired to the pulse power board & to other external components. The transmitter case can be cut down to an overall depth of30mm (with the lid on) to make it easier to handle. This job should ideally be done using a docking saw, radial arm saw or handsaw but could also be done using a hacksaw & files. After mounting the receiver board on four integral pillars on the base of the case (next to the transformer), you will need to mount all the front panel hardware, including the Dynamark label. If the front panel has not been supplied pre-drilled, it will require holes and cutouts for the power switch, the meter, clip-in bezels for the LEDs, potentiometer VRl and the IR sensor diode. The meter is supplied with a drilling template for the large cutout required. This cutout can be made by drilling a series of small holes around the perimeter of the marked circle and then knocking out the hole and filing it to a smooth finish. The power switch hole can be made by drilling a large hole and filing it to shape. Now the Dynamark front panel label can be affixed to .the front panel. JUNE 1992 27 ••• A UXILIARY 2 •• •• TRACK F/R OFF 3 4 5 OI L e· ACK The infrared receiver diode (IRDl) should be positioned so that its active surface sits flush with the front panel opening. Take care to ensure that its leads are not shorted by the aluminium front panel label. Drill the holes for all the LED bezels and the potentiometer. The hole for the IRDl sensor is made large enough to allow the sensor to protrude slightly into the panel so that it sits flush with the front surface. The meter requires a new scale to be attached. This should be supplied with the kit but if you are not working from a kit, you should purchase the new meter scale when you obtain the Dynamark front panel. To install the new scale you will need to unclip the meter's front escutcheon and remove the two meter scale screws. Remove the old scale by sliding it under the meter pointer, then attach the new one with the meter scale screws. Once all the components are mounted on the front and rear panels, you can complete the wiring by following Fig.11 , presented on page 84 of last month's issue. We used medium-duty hookup wire for all connections, except for the LED wiring and the 1-6 terminal wiring between the pulse power board and the receiver PC board where we used rainbow cable. Note that LEDs 1-5 each require a lkQ resistor in the cathode (K) leg. These resistor leads should be kept short. Note that all wiring must be kept away from the back of the IRDl infrared detector diode. If any wiring is run near this component, the remote control range will suffer drastically. Testing Once the wiring is complete, check your work carefully before switching Fig.15: full size etching pattern for the transmitter PC board. 28 SILICON CHIP on the power. Set all the trimpots initially to mid setting. Once the power is on, you can check the supply rails with your multimeter. We will assume that you have already checked the voltages on the pulse power board but it won't hurt to run through them again now that all the wiring is finalised . For the receiver PC board, connect your common meter lead to earth and check that there is +7V on pins 12, 13 & 14 of ICl, pin 8 of ICZ, and pin 8 of IC3 . There should also be +12V on pin 7 of ICl and pins 5 & 16 of ICZ. Check that there is +12V on pin 16 of IC3, pin 14 ofIC4, pin 8 ofIC5, pin 14 ofIC6, pin 14 ofIC7 and pin 14 ofIC8. If these measurements are not within about ±10% of the nominal value, switch off the power and check for wiring mistakes. Now checks can be made with the remote control. Pressing any button should light up the acknowledge LED. The faster button should bring the meter reading up while the slower button should bring the meter reading down. The auxiliary LEDs should operate when the relevant auxiliary switch is pressed. They should light only briefly if you have selected momentary operation and should stay on until the next button press if you have selected latched operation. Setting the trimpots The first trimpots to adjust are on the pulse power board. Connect your multimeter across the output terminals of the controller and press the faster switch until the voltage is at maxim1,1m. Adjust VRl for a reading of +12V. Now press the slower switch until the voltage reading is at a minimum. Adjust VRZ for an output of 1.5V or thereabouts. This trim.pot may need further adjustment when you start operating trains. If your locomotives start with a very small voltage across the track, you may want to set VRZ for 0V to stop the locos buzzing or creeping forward very slowly when they are supposed to be stationary. Trimpot VR6 adjusts the full scale calibration of the throttle setting meter. To adjust this, rotate the inertia control VR4 fully anticlockwise and then press the faster switch on the remote control to bring the throttle setting to a maximum. Now adjust VR6 until the meter reads full scale. Telecom would like to help you develop it. 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If you'd like to know more about the Telecom Product Development Fund, call Telecom's Technical Liaison Office on 008 033 673 or send in the attached coupon. = r---------~-------, Telecom Australia I I I I I I I I I I I I I I Please send me an information package NAME COMPANY A~ru POSTCODE L Send to: Manager Telecom Product Development Fund PO Box 249, Clayton, Victoria 3168 ccoso;sc I -----------------ii.I Australian and O verseas Te!ecommu nica tions C orporati on Limited A. C.N . 051 775 556 TRAIN + + SLOWER FASTER + STOP + + REVERSE FORWARD REMOTE TRAIN CONTROLLER ~ Fig.16: here are the full size artworks for the two front panels for the meter scale. & Note that any change in adjustment of VRl and VR2 on the pulse power PC board will affect this calibration and VR6 will then require re-adjustment. Trimpot VR4 sets the forward/reverse disable threshold. It should be set so that the FIR Off LED comes on when your locos are barely moving forward or have just come to stop. Adjustment is easier when the inertia control (VR4) is set to a minimum. Trimpot VR5 sets the rate of braking. We suggest that you leave this at mid-setting until you have had a chance to run your trains for a while. After that, you will probably want to increase the braking distance as you become more experienced with the remote controller. SC 30 SILICON CHIP