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Retro-fit any push-button garage door for remote control! WIRELESS REMOTE CONTROLLER Do you have a motorised garage door (or two!) which you open by pressing a wired-in pushbutton switch? Wouldn’t it be nice to be able to press a remote control button in your car as you drive towards it? (It’s great for cold, rainy nights . . .) This project will do just that for you. M One other important word in the last paragraph is “briefany homes have electrically-operated garage doors, gates, etc, usually powered by 230VAC ly”: invariably, the garage door controller is looking for a mains. But invariably the pushbutton switch to very brief switch closure – anywhere from a few millisecraise/lower or open/close them is controlled by a much onds up to, perhaps half a second. One thing it does NOT want is a permanent-until-pressedsafer low voltage – usually 5V or 12VDC. That’s why you’ll find the vast majority of controller again action a such as you would get from a latching-type pushbutton switches connected to the controller via bell switch. In normal electronics parlance, it wants a “mowire, mini figure-8 or even a couple of strands of rainbow mentary” action. cable, none of which would be anything like mains rated. So you should be able to tinker with the pushbutton side Adding remote control Because the up/down/stop switch is simply a pushbutof the controller to your heart’s content, knowing you’re ton, other switches can be and often are, wired in parallel. not going to get yourself across any nasty voltages! The pushbutton switch is almost always a single pole, For example, as well as a switch inside the garage, there normally-open type; more often than not it is a simple may well be a switch in the house itself so that you don’t “doorbell”-type switch. When pushed briefly it will raise have to go into the garage to close the door. Or there may even be one hidden outside if there is no the closed door, lower or close the open door, or stop the door from opening or closing further if the switch is pushed internal house-to-garage access. Or there may be a switch at the doorway into the garage so you mid-way through its travel. (The latter have to squeeze past any vehiis quite important if accidents – such as Design by Branko Justic don’t cles to get to the normal switch (often squashed children, pets, toys etc – are Words by Ross Tester installed at or near the door[s]). to be avoided!). 72 Silicon Chip Australia’s electronics magazine siliconchip.com.au One person we know has just this setup but he’s also wired in a hidden magnetic reed switch. His wallet has a tiny magnet in it which normally keeps the magnetic flap closed – but if he’s outside and wants to open the garage door, he simply waves his wallet close to the reed switch and . . . presto! (Anyone hoping to find out how he achieved the wallet magic wouldn’t have a clue!). All of these switches are simply wired in parallel and, as we said earlier, the connecting wires are usually pretty light gauge. They carry very little current. So it stands to reason that if you want to add wireless remote control, its (momentary) output would also be wired in parallel with one of the other switches. And that’s exactly what we’ve done with this remote controller. What if your garage already has one? Doesn’t matter! You can add this one to an existing controller, especially if you’ve lost or broken the remote (see above right!) or even if the existing remote controller itself has failed. You could save a fortune! As it simply goes in parallel with the existing push button, you could also use it as a much cheaper way to give another family member remote access. The existing controller won’t be affected. In fact, I know someone who put one of these in his garage even though the existing one worked fine – he said it was a LOT cheaper than buying extra “brand name” handheld remote control units for his family members! We have to be honest – you can buy ready-made UHF remote controllers, transmitters and receivers, online for much the same price (and sometimes lower) than the kit we’re using. Lost your remote control? Talk about coincidence (or Just the other day a colleagueis it Karma?). rang me bemoaning the fact tha(g’day Dave!) tenants had “done a runner” lea t his trusted ving him in a bad way. Losing the rent owing was bad he went on to say that they’d als enough, then with the only garage door rem o absconded “It’s a really old system and theote controller. those controllers any more. I’ve y don’t make more than five hundred dollars been quoted to replace it,” he moaned. “Have I got some good new said. “I can solve your problem s for you,” I for less than fifty bucks . . . “ But that means you won’t have the thrill (or practice) of building something yourself. And you won’t have much of an idea how or why it works. Which is why we’re suggesting using this kit of parts. And one point that many online buyers now miss: since July 1 you now have to add GST to the online prices and the freight, which might make that “attractive” price The controller While we have presented a number of UHF remote controllers over the years, we’re going down this route because ready-made UHF transmitters and receivers have now reached an almost give-away price. For example, the assembled TX10 transmitter PCB from Oatley Electronics sells for just $8.00 in a fourbutton keyfob, as seen below! The matching highsecurity receiver will set you back just $5.00. Or you can buy the complete K180XPX kit – two transmitters, receiver plus the decoder/relay driver PCB and all the bits you need (four relays, LEDs, power supply components, etc) along with a suitable plugpack supply for just $40.00 plus p&p. Two key fob transmitters are shown here, one with its protective cover closed (to prevent accidental presses) and the other open, ready for action. Another modulebased transmitter is also available but these are the ones we prefer. siliconchip.com.au Fig.1: the controller PCB also contains the pre-assembled UHF receiver/decoder along with the 9VAC/12V DC power supply, powered by an external plugpack. You have the choice of building for one, two, three or four channels. Australia’s electronics magazine September 2018  73 a little less competitive! There are three parts to the K180X kit: (a) The transmitter, which is supplied pre-built and mounted in a key fob with four push-buttons. Depending on which button is pressed, it sends a coded signal in the 433MHz band. (b) The 433MHz receiver module itself, which is also supplied pre-built, ready to mount on (c) The controller PCB, which simply accepts the decoded signal from the receiver, turning on the appropriate relay (one of four). We should mention that an alternative transmitter, the TX10 module, is also available but we believe the keyringmounted transmitter will be much more popular. However, some readers may have other applications for the remote control system so we mention it in passing only (see the Oatley Electronics website [www.oatleyelectronics.com] for more details). Switching mains voltages A word about the controller: while the relays are labelled as “10A, 250V” we don’t believe you should be trying to switch mains voltages with this project. As we said earlier, the switching side of (we believe) ALL garage door controllers is done at low voltage so there is no need to provide the extra insulation and care needed for a mains-switching project. If you want to adapt this project for another use which does involve switching mains, our advice is to be extremely careful – it is something you should only do if you have experience in building projects involving high voltage. In other words, it’s not something for a beginner to undertake, whereas the project as it stands is ideally suited for those with little construction experience. To be frank, we would prefer to keep this solely as a lowvoltage switching device; if you want to switch mains we would be much happier to see it used in conjunction with a mains relay board (ie, the relay switching another relay). We have published two projects specifically designed for this (It’s certainly not a new problem!). The first was back in May 2006 – a Remote Mains Relay (siliconchip.com.au/Article/2665). It used either a switch or closing contacts to control a beefy (10A, 250V) relay on a PCB with widely-spaced tracks. Unfortunately, though, it was prepared in conjunction with Dick Smith Electronics so for obvious reasons is no longer available. If there is demand, we may revisit this in the future. The second, the Remote Mains Relay MkII of January 2009 (siliconchip.com.au/Article/1272), was slightly more complicated but it offered more features, including a relay rated at 20A, 250V and all but the mains input and output sockets mounted on one large PCB. This PCB, code 10101091, was the same as used the USB Sensing Power Switch in January 2009 siliconchip.com. au/Article/1441) and is still available from the SILICON CHIP Online Shop. All components used in this project are common, garden-variety devices and should be available from your usual supplier. Incidentally, you may be wondering why most relays have a much higher AC switching rating than their DC rating. For example. the “Songle” brand relays used in this project have a rating of 10A at 250VAC or 28V DC. The reason is simple: when the contacts open and they 74 Silicon Chip interrupt a high current, they will usually draw an arc which could weld the contacts closed – not exactly what you want. For 50Hz AC, the voltage drops to zero every ten milliseconds so there is nothing to keep the arc going. But with DC, the voltage stays constant so the arc may continue. The problem is worse the higher the voltage so the rating for DC is reduced to about 10% of the AC voltage. How it works Let’s put the cart before the horse and look at the receiver/relay board first of all. It is shown in Fig.1. It has a bog-standard power supply on board which can handle either an input supply of 9VAC or 12V DC. It does this by putting the input supply through a small bridge rectifier (BR1), smoothed by a 100µF electrolytic capacitor. This provides the ~12V DC required to power the relays. (9VAC x 1.4142 = ~12.7V DC, less the losses across the diodes in the bridge rectifier.) And because of the bridge rectifier in circuit, the supply voltage (if DC) can be connected with either polarity. Following the bridge is a 7805 positive regulator, the output of which is smoothed by another 100µF capacitor. This gives the 5V supply which powers the rest of the circuit. The 5V DC is also brought out to one of the terminals on the 3-way power socket – it can be used for other peripherals requiring a regulated 5V DC supply. The other two terminals accept the AC or DC input. A tiny 433MHz receiver module wired to the PCB receives a coded signal – from up to perhaps 10m or so away – from the matching transmitter. The (prebuilt) transmitter module has four push buttons so you can have up to four “channels” being controlled. The RX480R-4ch receiver module similarly has four outputs which drive up to four small relays via a ULN2003 relay driver. This actually has seven inputs and outputs; we are only using five. Hang on – didn’t we just say this is a four channel system? That’s true, only four of the ULN2003 outputs are connected to relays. But a fifth output, called the “VT” output can be used to verify that a valid transmitter signal has been received (hence the name – VT). While it is left unconnected in this circuit, it could be used to drive “something else”. For example, you wanted to activate that “something else” Inside the TX10 key fob transmitter, shown here mainly to reveal what happens when a battery’s insides like to explore the outside world! The four white buttons are actuated by the flexible membranes on the key fob top. Australia’s electronics magazine siliconchip.com.au The receiver module is tiny, as this photo shows. The white pushbutton at top right is the programming switch. if any key on the remote control transmitter was pressed. Note that this is equivalent to a “NC” output – ie, it is normally high and goes low when a button is pressed and a valid signal is received. When the button is released, it goes high again. Naturally, the other four outputs independently switch their on-board relay if, and only if, the appropriate push button on the remote control transmitter is pressed. Well, even that is not absolutely true because one of the three modes of operation is to “latch and reset” – the button pressed activates the appropriate relay but at the same time resets the other three relays if they are currently activated. Bearing in mind our earlier comments about not being recommended for mains switching, each of the four relays has a normally-open (NO), normally-closed (NC) and common terminal. To use it like you would use a switch, you would connect between the NO and common terminals. Along with the relays, the ULN2003 also powers four LEDs (one per relay) to give a visual indication of the relay being pulled in. There is no such indication on the VT output, though this would be easy enough to arrange if you wanted one (eg, via a LED and 2.2kΩ resistor in series connected to +12V). Incidentally, if you only need one channel you only need to solder in one relay and one set of terminals; two for two and so on. Fig.2: component overlay and matching photo of the receiver/ controller PCB. The receiver must go into the board as shown! Momentary or latching relays Invariably, commercial garage door controllers are activated by a brief press of a “momentary” pushbutton switch (perhaps for half a second or so). You definitely do not want the switch to stay on once you remove your finger, if only for the simple reason that you would not then be able to open or close the door (it would stay open or closed while ever the switch was “on”). Perhaps even more importantly, there are some garage door controllers which warn that holding the pushbutton on for a long period risks the control circuit being damaged. That’s a remote (pardon the pun!) possibility but a possibility neverthess. So we set up the remote controller to mimic the momentary switch. This is done when you program the receiver module. We mentioned earlier the “latch and reset” mode. In case you haven’t worked it out by now, the other two modes are simply “momentary” or “latch”. The transmitter Let’s now look at the transmitter module. As we mentioned, there are actually two available – one a module to be constructed but the more convenient is supplied preassembled. It’s in a small keyfob and has of four user buttons (A, B, C & D) protected by a sliding cover (to prevent inadvertent pressing!). The A and B buttons are larger; presumably they’d get the most use. A tiny LED pokes through the front of the siliconchip.com.au module to show when any button is pressed. We’ve shown the internals of a TX10 transmitter, if for no other reason than to reveal a trap for young players. If you look carefully at the negative end of the battery in this photo, you can see that some of its insides are now . . . outside! Fortunately, this one has not gone too far and is salvageable but you might not be so fortunate! The problem is that, like many devices coming out of China with batteries supplied, their quality is often questionable (it’s certainly not the first leaky battery we’ve seen!) and you have no idea how old the battery is anyway. To be frank, we’d throw away the battery and replace it with a fresh, known brand (eg, Eveready or Duracell etc). Sure, that might seem like you’re wasting a battery, but . . . Meanwhile, back at the ranch . . . The K180X is one clever system! Unlike some el-cheapo modules, it uses a rolling code which has around one million possibilities. And it changes its code every time it is used so that in the unlikely event your code was recorded off-air (and there are plenty of 433MHz receivers around which could do it), using the same code again will have no effect. The code-hopping happens automatically; once you Australia’s electronics magazine September 2018  75 have set the transmitter to match the receiver (and we’ll get to that shortly) you don’t have to worry about it again. Construction Only the K180X controller PCB needs to be assembled – as we mentioned earlier, the preferred transmitter is supplied pre-built and ready to rock. The tiny 433MHz receiver module is also pre-built and only needs to be soldered in place on the main (controller) PCB. Follow the PCB component layout, Fig.2, and its matching photo. Start with the resistors, electrolytic capacitors and LEDs, followed by the regulator IC and the bridge rectifier. Obviously, watch the polarity for the capacitors, LEDs, regulator and bridge. The top side of the PCB is clearly marked. Also solder in the 3-way “power” terminal block – make sure its access holes point outwards towards the edge of the PCB. The ULN2003 is the last “component” as such to go in – again, it must be inserted with the notch on the IC matching the notch on the PCB. All that’s left are the relays and the terminal blocks. Their terminal pins will only allow them to be inserted one way. As we mentioned earlier, if you only need one channel, simply install relay A and its associated components. It’s more than likely that your existing garage door controller will also switch on a light for a preset period – and this will still happen so you don’t have to get involved with mains wiring. The terminal blocks come in sets of three – to fit on the PCB, you will need to slide the tongue and grooves on their sides together. Again, the access holes point outwards. An antenna There is no provision on the receiver PCB for an antenna track so you’ll need to add one, preferably before soldering in the receiver module (it can be done later but it’s a bit easier now!). The antenna connection point is clearly marked on the back of the PCB, diagonally opposite the other connections. 433MHz has a wavelength around 700mm; a quarterwave antenna (~173mm) made from a length of fine hookup wire would be fine. This could be left straight, dangling from the PCB, or if you’re putting the controller/receiver in a case, could be curled around into a coil (exact size is not important). It’s only if you’re after absolute maximum range that the length of the antenna becomes more critical. Just make sure you don’t have any bared end of the antenna wire to short onto anything else. The receiver The tiny RX480R receiver module solders in vertically with the component side toward the edge of the controller PCB (it is possible to put it in back to front but it certainly won’t work and more than likely will be damaged. So check twice before soldering!). Our photo and component overlay (Fig.2) shows the orientation clearly. A case? We assume the receiver/controller will be mounted inside the garage, if not close to the garage door controller switch then close to a power outlet. But even though it might be out of the elements, we’d be inclined to mount it 76 Silicon Chip inside a small case to protect it from moisture, dust, critters etc. Unfortunately it’s just too big to fit into Oatley’s HB1 Jiffy Box but it fits easily into their HB2 Jiffy Box (130 x 67 x 42mm). That box is only $3.50 and we consider it a sensible investment (order at the same time as you order your K180X kit to save on postage). There are four holes drilled in the corners of the PCB (on a 76mm x 63mm rectangle) which make for easy mounting. You’ll also need to provide small access holes for the power leads, the wiring to the door controller switch and, if you wish, an external antenna. Each of these are on different sides of the PCB so they won’t get mixed up! Once the unit is built and tested, we’d put a dollop of silicone sealant over the holes, again to stop little pests making their home inside. Programming It’s not so much programming as selection of operating modes (as discussed earlier – momentary, toggle and toggle with reset). Once the receiver learns the mode, it stays set that way until changed. The same is true for the codes – the receiver knows what code to expect. Apply power to the receiver. Absolutely nothing should happen! While the receiver should be devoid of any memory, you can ensure it is cleared by pressing the tiny reset pushbutton switch (directly opposite the antenna terminal) eight times. The LED will flash eight times to confirm this. Then the receiver can be programmed to operate as follows: For momentary mode, press the button ONCE and the LED will light. Now press any button on the transmitter. Each of the receiver relays will operate when their corresponding transmitter button is pressed and release when the button is released For latching mode, press the button TWICE. Again, the LED will light. Press any button on the transmitter and each of the relays will then operate when their corresponding transmitter button is pressed but not release until the same transmitter button is pressed again. For latching with reset mode, press the button THREE TIMES. As before, the LED will light and the relay associated with that push button will pull on, while all other relays will release. The same applies to any other relay and its pushbutton. SC Where from; how much: There are several options available. You can purchase only the receiver ($5.00 each) or only the controller PCB with receiver and components ($26.00 each) or only the prebuilt key fob tran-smitter ($8.00 each) if you wish. We’d have to ask why you’d want the separate components (except, perhaps, to get extra key fob transmitters). By far the best option is to purchase the full K180XPX kit, which not only gets you all of the above, you get a second key fob transmitter and a suitable mains plugpack, all for the princely sum of $40.00 plus P&P. As we mentioned in the text, we’d also add an HB2 Jiffy Box at the same time ($3.50) and save a bit on p&p. More information is available on Oatley Electronics website (oatleyelectronics.com). Australia’s electronics magazine siliconchip.com.au