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Remote controller for garage doors The circuit presented here has all the required elec­tronics for a garage door opener or other motorised device. It features a 304MHz UHF remote control transmitter, the receiver & decoding circuitry, door logic & motor switching relays. Design by BRANCO JUSTIC We last featured a remote controller for garage doors in the March and April 1991 issues of SILICON CHIP. This new project updates that design with completely new circuitry and the main PC board has fewer components on it too. The main features of the circuit are provision for upper and lower limit door travel switches and over-current sensing for UP and DOWN modes of 16  Silicon Chip operation. This latter feature can be used to detect obstructions and immediately stop door operation to prevent damage to the motor, drive mech­anism or possibly even your car. The unit is based on a pre-built (and pre-aligned) UHF receiver module and features a small keyring transmitter that has more than half a million possi­ble codes – 531,441 to be precise. You press the button on the transmitter and the door goes up; press it again and the door goes down – no more getting out of the car to open the garage door! The circuit has provision for a manual switch which can be mounted somewhere on the wall inside the garage. This works in a similar way to the button on the transmitter: press it once for the door to go up and press it again to make the door go down. If you press the button before the door reaches the end of its travel, it will stop. You then have to press the button again to make the door go in the opposite direction. This applies also to operation via the transmitter. Rather than re-invent the wheel, both the transmitter and the pre-built receiver front-end are the same as used in the UHF Remote Switch project that was featured in the December 1992 issue of SILICON CHIP. The front-end D1 1N4148 18 S1 HIGH LOW A LED1 λ K 12V R4 82 Ω 1 2 3 4 5 6 7 8 10 11 12 13 L1 ETCHED ON BOARD C1 .001 A1 A2 R2 6.8k 17 C B E R3 1k A3 C2 .001 A4 C4 6.8pF C3 2-7pF 304MHz SAW FILTER C5 4.7pF Q1 2SC3355 R5 150 Ω A5 A6 IC1 AX5026 A7 A A8 K A9 15 A10 C E B VIEWED FROM BELOW 16 R1 1M A11 A12 UHF REMOTE CONTROL TRANSMITTER 9 14 Fig.1: the transmitter is based on trinary encoder IC1. When S1 is pressed, IC1 generates a series of pulses at its pin 17 output to switch transistor Q1 on & off. This transistor is wired as an oscillator & operates at 304MHz due to its tuned collector load & the SAW filter in the feedback path. module of the receiver comes prealigned (to 304MHz) and uses surface mount components to give an assembly that measures just 35 x 25mm. It is fitted with a pin connector along one edge and plugs into the receiver PC board just like any other component. This eliminates alignment hassles and means that you don’t have to wind any tricky coils. How it works – transmitter The transmitter is based on an AX5026 trinary encoder IC – see Fig.1. When pushbutton switch S1 is press­ ed, this IC gener­ ates a sequence of pulses at its output (pin 17). The rate at which these pulses are generated is set by the 1MΩ timing resis­tor between pins 15 and 16 (R1), while the code sequence is set by the connections to the address lines (A1-A12). Each of these address lines can be tied high, tied low or left open circuit (O/C), giving 531,441 possible codes. The pulse coded output from IC1 drives RF transistor Q1. This transistor is connected as an oscillator and operates at 304MHz, as set by a tank circuit consisting of L1 (etched on the PC board), C3, C4 and C5. In addition, a SAW (surface acoustic wave) resonator is used to provide a narrow-band feedback path. Its lowest impedance is at its resonant frequency of 304MHz and thus the tuned collector load must be set to this frequency in order for Q1 to oscillate. The SAW resonator ensures frequency stability and makes the transmitter easy to align. It ensures that the oscillator will only start and pulse LED 1 when the tuned circuit is virtually dead on frequency. C3 is used to adjust the centre frequency of the tuned circuit. This point corresponds to maximum current consumption and is found by adjusting C3 to obtain peak brightness from the indicator LED (LED 1). Power for the transmitter is derived from a miniature 12V battery (GP23 or equivalent) and this is connected in series with the pushbutton switch (S1). When S1 is pressed, the current drawn by the circuit is only a few milliamps, the exact figure depend­ing on the code word selected at address lines A1-A12. How it works – receiver Fig.2 shows the circuit details of the receiver. Its job is to pick-up the coded RF pulses from the transmitter and decode these pulses to generate an output. As already mentioned, the receiver is based on a complete “front-end” module. This processes the received signal via a bandpass filter, an RF preamplifier, a regenerative detector, an amplifier and a Schmitt trigger. Its input is connected to a short antenna, while its output delivers a digital pulse train to the input (pin 14) of IC1. IC1 is an AX-528 Tristate decoder and is used to decode the 12-bit pulse signal that’s generated by the transmitter. As with the AX-5026 encoder, this device has 12 address lines (A1-A12) and these are connected to match the transmitter code. If the code sequence on pin 14 of IC1 matches its address lines, and the code sequence rate matches its timing (as set by R1), the valid transmission output at pin 17 switches high. This output connects via diode D1 to the December 1993  17 18  Silicon Chip +12V 0.1 2 7 RLA1 5 CODING LINES M 0. 22 5W RLB2 DOOR MOTOR 0. 22  5W RLB1 1,3,6,8,10, 11,12 RECEIVER MODULE RLA2 ANTENNA 0.1 3 14 13 12 11 10 8 7 6 5 4 10 100k 100k 10 100k 100k +12V 1 2 100k VR2 220k 180k 100k VR1 220k 180k 9 IC1 AX528 18 6 5 2 3 1M IC4b IC4a LM358 15 16 17 4 8 D1 1N914 MANUAL S1 7 10k 1 10k +8V .01 0.1 D13 1N914 +8V D12 1N914 1M LIMITS S2,S3 3.3M 10M IC3b 6 5 AC INPUT +8V D10 1N914 100k 100  5W D11 1N914 D16 D17 220k D3 1N914 13 14 10 15 D15 D14 Q3 Q1 2 1 1000 100k IC3a 8 IC2 4017 4x1N5402 10 3 ENA CLK Q4 RST 16 GARAGE DOOR CONTROLLER 4 D2 1N914 0.1 7 2 B1 12V 100k 0.1 0.1 13 1000 D18 1N4004 IC3d 100k D4 1N914 4.7k B 12 D6 1N4004 D5 1N914 +8V E 11 OUT GND 10 IC5 78L08 D8 1N914 D9 1N914 D7 1N4004 4.7k GND C IN VIEWED FROM BELOW IN B 10M Q1 BC337 10 E C RLA OUT +8V +12V 9 IC3c 4093 8 Q2 BC337 B 7 14 E C D 10 +8V GDS RLB 10  +12V LAMP G Q3 MTP3055 S D +12V PARTS LIST Transmitter 1 transmitter case 1 PC board, 30 x 37mm 1 miniature PC-mount pushbutton switch 1 12V battery, GP23 or equivalent 1 304MHz SAW resonator Semiconductors 1 AX-5026 trinary encoder (IC1) 1 2SC3355 NPN transistor (Q1) 1 1N4148 silicon diode (D1) 1 3mm red LED (LED1) Capacitors 2 .001µF ceramic 1 6.8pF ceramic 1 4.7pF ceramic 1 2-7pF miniature trimmer Resistors (0.25W, 5%) 1 1MΩ 1 150Ω 1 6.8kΩ 1 82Ω 1 1kΩ Receiver 1 PC board, 144 x 87mm ▲ clock input (pin 14) of IC2, a 4017 decade counter. This counter can also be clocked by manual switch S1 and by limit switch­ es S2 and S3. The length of the clock pulses produced by the operation of S2 and S3 is limited by the time constant of the associated 0.1µF capacitor and 3.3MΩ resistor. The .01µF capacitor filters out any noise picked up by the wires used to connect S1, S2 and S3, while the 10MΩ resistor discharges the 0.1µF capacitor after S2 or S3 has been operated. Fig.2 (left): the heart of this circuit is IC1 & IC2. IC1’s output at pin 17 goes high when a valid code is detected. Pin 17 then clocks IC2 which controls the switching of relays RLA & RLB via transistors Q1 & Q2. IC4a & IC4b provide over-current monitoring & they can clock IC2 into a STOP mode whereby the relays are not energised. IC3d, IC3c & Q3 light the lamp for about two minutes after the transmitter button is pressed. 1 front-end module (aligned to 304MHz) 2 12V DPDT relays 1 momentary contract pushbutton switch (S1) 2 microswitches (S2,S3) 1 12V SLA battery 1 12V lamp 4 2-way insulated terminal blocks 1 3-way insulated terminal block 2 100kΩ trimpots (VR1,VR2) Semiconductors 1 AX-528 tristate decoder (IC1) 1 4017 decade counter (IC2) 1 4093 quad Schmitt NAND gate (IC3) 1 LM358 dual op amp (IC4) 1 78L08 3-terminal regulator 2 BC337 NPN transistors (Q1, Q2) 1 MTP3055 Mosfet (Q3) 4 1N5404 rectifier diodes (D14-D17) 11 1N914, 1N4148 signal diodes (D1-D5,D8-D13) 3 1N4004 rectifier diodes (D6,D7,D18) Note that when the power is first applied, IC2 is reset by a short pulse on the reset line, by virtue of the 0.1µF capacitor connected to the +8V supply line. The counter is also reset when its Q4 output goes high; a pulse is applied to the reset input via diode D3. This means that IC4 can only have four exclusive output states: Q0 high, Q1 high, Q2 high or Q3 high. Outputs Q0 and Q2 do not drive anything so they correspond to “Stop” modes while outputs Q1 and Q3 switch the “Up” and “Down” relays (via transistors Q1 & Q2). Thus, a succession of clock pulses from decoder IC1 correspond to the following modes: Stop, Up, Stop, Down, Stop, Up, etc. Two separate over-current detectors, comprising op amp com­parators IC4a and IC4b, detect higher than normal motor currents that would result when the door reaches its Up or Down stop positions or if the door is obstructed. The outputs of these over-current detectors then apply a pulse to the clock input of IC2, which causes it to go into the Stop mode. Capacitors 2 1000µF 16VW PC mount electrolytic 5 10µF 16VW PC mount electrolytic 6 0.1µF monolithic 1 .01µF monolithic Resistors (0.25W, 5%) 2 10MΩ 2 10kΩ 1 3.3MΩ 2 4.7kΩ 2 1MΩ 1 100Ω 5W 3 220kΩ 1 10Ω 2 180kΩ 2 0.22Ω 5W 8 100kΩ Where to buy the parts A kit of parts for this garage door controller is avail­ able from Oatley Electronics, PO Box 89, Oatley, NSW 2223, Aus­tralia. Phone (02) 579 4985. The prices are as follows: (1) Receiver kit (PC board and all on-board com­ ponents) $79; (2) Transmitter kit (including case & battery) $19; (3) 17V AC plug­pack $18. Add $2.50 for postage & packing. The counter can be disabled from clocking by its ENA-bar input being held at “0”. The output of the mono­ stable comprising Schmitt NAND gates IC3a & IC3b is normally high, thus enabling the counter to clock. However, this monostable is triggered via isolating diodes D4 & D5 each time Q1 (up) or Q3 (down)of IC2 first go high. This monostable therefore prevents the counter from stepping for approximately two seconds after the Up or Down modes are first activated. This two-second disabling of the counter prevents it being triggered by the over-current detectors, which would otherwise happen since a motor draws relatively high cur­rents when it first starts up. Courtesy lamp driver A second monostable made up of gates IC3c & IC3d is used to switch a lamp via Mosfet Q3. This monostable is also operated via diodes D4 and D5 each time Q1 (up) or Q3 (down) of IC2 goes high. The time constant of the monostable causes the lamp to light for just under two minutes. December 1993  19 A .001 S1 D1 K 6.8k C3 6.8pF LED1 K 82  A 1k 1M Q1 4.7pF SAW 150  .001 IC1 AX5026 1 12V BATTERY Fig.3: keep all leads as short as possible when installing the parts on the transmitter PC board & take care with the orientation of the encoder IC. A combination of a 12V battery and a 17V 1A AC plugpack are used to power the controller. The 100Ω 5W resistor in series with the bridge rectifier limits the charging current to the battery. Note that the two 1000µF capacitors in the power supply are rated at 16VW but if the 12V battery is not present that voltage rating will be exceeded. A 7808 3-terminal regulator provides a +8V supply for the receiver, decoder and op amps, while the relays and motor are driven directly from the 12V battery. Note that each relay has two pairs of contacts to connect the motor across the 12V supply in one direction or the other. The system is fail-safe since only one relay can be energised at a time and when the circuit is in Stop mode, both relays are de-energised and the motor is isolated from the 12V battery. Construction Let’s discuss the transmitter first. The component layout for the PC board is shown in Fig.3. All the parts, including the battery terminals and the switch (S1), are mounted on a small PC board which fits inside a plastic transmitter case. Before mounting any of the parts, you must first file the edges of the PC board so that it will fit in the case. The receiver is based on this pre-built front-end module which comes ready aligned & tuned to 304MHz. It is soldered into place on the PC board just like any other component. 20  Silicon Chip This also removes two shorting strips. One of these strips runs along the bottom of the board, while the other runs down the righthand edge (as viewed from the copper side). Make sure that these two short­ing strips are completely filed away; if they are not, the bat­tery terminals will be shorted and the positive battery terminal will be shorted to C3. The most important thing to remember with the transmitter assembly is that all component leads should be kept as short as possible. Apart from that, it’s simply a matter of installing the parts as shown in Fig.3. Be sure to orient IC1 correctly and note that the flat side of the trimmer capacitor (C3) is adjacent to one end of the board. The SAW resonator and switch should both be mounted flat against the board, while the transistor should only stand about 1mm proud of the board. Take care when mounting the switch – it must be correctly oriented, otherwise it will appear as a short and the transmitter will be on all the time (the switch will only fit comfortably in one direction). The LED should be mounted with its top about 7mm proud of the board, so that it later protrudes about halfway through a matching hole in the lid. Be careful with the orientation of the LED – its anode lead is the longer of the two. Check the board carefully when the TO MOTOR 0.1 3.3M 100k 0.1 IC2 4017 100  5W D3 10uF 10  VR1 100k A 1 10uF 10uF 0. 22  5W IC5 10uF D7 1000uF D13 100k 180k 220k 10k 10M D8 D6 100k 180k D12 10k IC4 LM358 100k 100k 100k 4.7k 4.7k 0.1 D9 RELAY B Q2 LAMP LIMIT SWITCH Q3 S DG Q1 220k D11 IC3 4093 220k D10 0.1 1 100k A 10M 10uF 0.1 D5 0. 22  5W RELAY A D4 TP TO S1 1 .01 0.1 ANTENNA D2 1M 1M D1 IC1 AX528 RECEIVER 1 BOARD 0.1 AC POWER BATTERY D18 1000uF VR2 D14-D17 Fig.4: the front-end module is installed on the receiver PC board with its component side facing the adjacent 0.1µF capacitor. Don’t forget to install the two insulated wire links (shown dotted) on the copper side of the PC board. assembly is completed – it only takes one wrong component value to upset the circuit operation. This done, slip the board into the bottom half of the case, install the battery and test the circuit by pressing the switch button. Don’t worry if the LED doesn’t flash at this stage – that probably won’t occur because Q1 will not be oscillating. To adjust the oscillator stage, press the switch and tune C3 using a plastic tool until the LED does start to flash. When this hap­pens, the oscillator is working and you can tweak C3 for maximum transmitter output (ie, max­imum LED brightness). The lid of the case can now be snapped into position and secured using the small screw supplied. Receiver assembly Fig.4 shows the parts layout on the receiver board. Install the parts exactly as shown, leaving the receiver module till last. This module must be installed with its component side away from the AX528 decoder (IC1). Do not forget to install the link underneath IC1 or the insulated link which runs from the anode of D18 to the common­ed connection to the two relays (+12V). A second insulated link runs from the cathode of D13 to point A below the front-end module. The antenna consists of a length of insulated hook-up wire and can be either 250mm or 500mm long. The latter will give slightly greater range. When the receiver assembly is complete, check all your work carefully to see that it agrees with the wiring diagram of Fig.4. This done, apply power and use your DMM to check that pin 17 of the AX528 switches high when the transmitter button is pressed. Coding Initially, all the A1-A12 address lines will be open cir­ cuit but you can tie selected address pins high or low by con­necting them to adjacent copper tracks. In both cases, a +5V rail runs adjacent to the inside edge of the address pins, while a ground track runs around the outside edge of the address pins. For example, you might decide to tie A1 and A8 high, tie A3 and A6 low, and leave the rest open circuit. Short wire links can be used to make the connections but note that you will have to scrape away the solder mask from the supply rail at each con­nection point so that the track can be soldered. Make sure that the transmitter code matches the receiver code otherwise the remote control won’t work. Note that the over-current setting trimpots (VR1 & VR2) are set during installation of the door mechanism. Full instruc­tions on installation and typical mechanisms were featured in SC the April 1991 issue. RESISTOR COLOUR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ No. 2 1 3 3 2 8 2 1 2 1 1 1 1 1 2 Value 10MΩ 3.3MΩ 1MΩ 220kΩ 180kΩ 100kΩ 10kΩ 6.8kΩ 4.7kΩ 1kΩ 150Ω 100Ω 5W 82Ω 10Ω 0.22Ω 5W 4-Band Code (1%) brown black blue brown orange orange green brown brown black green brown red red yellow brown brown grey yellow brown brown black yellow brown brown black orange brown blue grey red brown yellow violet red brown brown black red brown brown green brown brown not applicable grey red black brown brown black black brown not applicable 5-Band Code (1%) brown black black green brown orange orange black yellow brown brown black black yellow brown red red black orange brown brown grey black orange brown brown black black orange brown brown black black red brown blue grey black brown brown yellow violet black brown brown brown black black brown brown brown green black black brown not applicable grey red black gold brown brown black black gold brown not applicable December 1993  21