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The photo below shows how the small IR-ToUHF Converter board fits inside a universal remote control while at right is the companion UHF-To-IR Converter. By JOHN CLARKE Add a UHF link to a universal remote control Remote control extenders are old hat. Now you can add this tiny UHF module to your IR remote control and operate appliances from anywhere inside or outside your home. As well as the tiny module inside the remote, you also need our UHF-To-Infrared Converter which is positioned close to the device to be controlled. O VER THE YEARS, we have produced several infrared remote control extenders, the most recent being in October 2006. That project essentially received the IR signal from any remote control and the signal was then retransmitted using an IR LED that was attached to a long lead. This could be placed closer to the appliance being controlled (eg, in another room). More recently, there have been UHF remote control extenders. These receive the pulsed IR signal from the remote control and then re-radiate it at 2.4GHz. You then have a UHF receiver elsewhere in your home which picks up the 2.4GHz signal and converts it back to infrared pulses to be received by the appliance being controlled. Both approaches make sense but why not have a remote control that 64  Silicon Chip works at both infrared and UHF, rather than having a separate transmitter unit? So that is what this project is about. You build a tiny UHF module into the remote control and power it from the remote’s AA cells; there’s no external remote transmitter and power supply to worry about. Of course, you still need a UHF receiver/IR converter at the appliance end and that’s also described here. This approach is so much more convenient than past remote control extenders. For example, say you are out on the balcony having a pleasant lunch and the CD player is inside providing background music. Want to change a track and change the volume? No need to wander back inside, find the remote and then wander out again. You just pick up the same hand-held remote that you use inside and use it where you are. Both the UHF and infrared signals are radiated simultaneously, so it does not matter whether you are inside your home or outdoors. Sound like a good idea? We thought so too and this project is the result. We have designed a small PCB module that fits inside the remote control case. You will need to check that it will fit inside the remote control that you want to convert. Some remote controls will be too small or have very little room inside the case but many do have enough room, particularly universal remotes. What about current drain? But what about the extra current that will be drawn by the UHF module? siliconchip.com.au +3V + K TO 3V BATTERY IN REMOTE 1 F D1 1N4004 1k MMC 4 A – 1 Vdd MCLR/GP3 GP5 100 X 1 OPTO1 4N25 2 Y  6 ANTENNA 2 1 F 3 IC1 GP4 PIC12F6756 I/P GP1 47k 5 7 GP0 4 GP2 MMC TX1 433MHz TX MODULE DATA 5 Vss 1k Vcc 8 ANT GND 4N25 433MHz Tx MODULE SC 2013 1N4004 IR-TO-UHF CONVERTER A K ANT Vcc DATA GND 3 6 1 Fig.1: the IR-To-UHF Converter circuit. The IR LED driver circuit in the remote feeds the 38kHz signal in via OPTO1 and this drives pin 7 of PIC microcontroller IC1. The micro then powers and drives the 433MHz transmitter module (TX1). Will it drain the cells by too much and greatly reduce their life? No-one likes having to continually replace batteries in remote controls. For this reason, we have been very careful with this aspect and the current drain is truly negligible. Typically, it will be just a few nanoamps although we measured one of our prototypes at just 200 picoamps! That’s much less than one thousandth of a microamp! Compare that with the typical microamp or so drawn by a remote control from its AA or AAA cells. Naturally, more current is drawn from the battery when transmitting both the IR and UHF pulsed signal but it still does not amount to much. In a typical universal remote, the average current while transmitting increases from 10mA with IR transmission alone to 12mA with both IR and UHF transmission – an increase of just 2mA. Since remote controls only draw significant current while buttons are being pressed, the overall extra current drain with UHF transmission added +3V is unimportant. The AA or AAA cells will still last their shelf life (years). The companion UHF-To-IR Convert­ er is housed in a small plastic case. At one end of the case it has a red acknowledge LED as well as an IR LED to retransmit the received UHF signal as an IR signal. As well, there is a 3.5mm socket to allow connection of an external IR LED (ie, via a cable). The converter runs from a 9-12V DC plugpack and it draws a maximum of 50mA when transmitting, so any 9-12V DC plugpack will be suitable. Circuit details Fig.1 shows the circuit of the IRTo-UHF Converter to be built into the remote control. It uses an optocoupler (OPTO1), a PIC12F675 microcontroller (IC1) and a tiny UHF transmitter module (TX1) which runs at 433MHz. As stated, it’s powered from the remote’s two AA (or AAA) cells (ie, 3V). The optocoupler is needed to allow for any of the possible LED drive arrangements and provides isolation +3V X A (b) K Y X X A 2.7 (TYP.) (a) from the rest of the circuit. The various possibilities are shown in Fig.2. The input of the optocoupler connects, via a 100Ω resistor, across the IR LED drive circuit on the remote control’s PCB. For example, in the Altronics A-1012 universal remote, the IR LED drive is as depicted in Fig.2(a). In this case, the “X” terminal input to the optocoupler connects to the +3V supply rail and the “Y” terminal connects to the cathode of the IR LED. For arrangements such as Fig.2(b), the +3V positive rail is easily accessible but the LED driver output needs to be picked off the series resistor itself. You may need to lift out the remote’s PCB to access this resistor. The optocoupler’s internal transistor is connected as an emitter follower, with its base tied to the emitter with a 47kΩ resistor to speed up switching. The resistor effectively discharges the transistor’s base each time the opto’s internal IR diode stops emitting (ie, at the end of each pulse in the 38kHz signal burst). This allows the transis- X A K (c) 2.7 (TYP.) Y 2.7 (TYP.) (d) K 2.7 (TYP.) A K Y Y Fig.2: the four possible IR LED driver arrangements in a remote control. The signal drive to the IR-To-UHF Converter must be taken from the points labelled “X” and “Y” (see text for determining the configuration of your remote). siliconchip.com.au July 2013  65 OUT ANTENNA 1k ANT Vcc 433MHz RX MODULE GND 4 DATA 2 CARRIER ADJUST VR1 10k 433MHz Rx MODULE MIN MCLR/GP3 1 Vdd GP0 GP5 GP4 GP2 100 F 16V A 220 A (ACK)  LED2 K 220 5 Vss 8 MAX 9–12V DC IN 1k 7 IC1 6 PIC12F675- GP1 I/P 3 CON1 A K IN GND 100 F 16V 100nF RX1 D1 1N4004 REG1 78L05 +5V CON2 EXTERNAL IR LED (IR LED)  LED1 SC 2013 Vcc DATA DATA GND ANT GND GND Vcc K LEDS UHF-TO-IR CONVERTER 1N4004 A K K A 78L05 GND IN OUT Fig.3: the UHF-To-IR Converter circuit picks up the transmitted 433MHz signal using RX1 and feeds it to PIC microcontroller IC1. IC1 in turn drives an infrared LED (LED1) and an acknowledge LED (LED2). tor to switch off faster than if its base were left floating. The opto’s emitter signal is applied to the GP0 input (pin 7) of microcontroller IC1. With no 38kHz signal burst present at pin 7, IC2 is in sleep mode. Its GP1, GP2, GP4 & GP5 outputs are all low, so transmitter TX1 is off and the circuit draws minimal power at around 12nA. At the onset of signal at pin 7, IC1 wakes up and sets its GP1, GP4 & GP5 outputs high (3V) to power up the UHF transmitter (TX1). IC1 also demodulates the 38kHz signal, so that the output at pin 5 is identical to the original modulation on the 38kHz bursts. TX1 transmits the UHF signal using a 170mm antenna which is just a length of hook-up wire. After a period of 600ms with no 38kHz signal, power to TX1 is removed with GP1, GP4 & GP5 going low. Using a microcontroller might seem like overkill for the circuit. However, it was chosen simply because it can be put to sleep and thereby draw negligible current from the remote control’s cells. Any other approach, such as using a couple of CMOS timers (eg, 7555), would have much higher current drain than the remote control itself. UHF-To-IR Converter The modulated UHF signal needs to be detected and converted back to a stream of infrared pulses to control the appliance being operated. For that we need the separate UHF-To-IR Converter referred to above. The converter circuit is shown in Fig.3 and comprises UHF receiver RX1, another PIC12F675 microcontroller (IC1) and an IR LED (LED1). The whole circuit is powered from 9-12V DC. The UHF receiver is powered continuously, so that it is ready to receive a transmission from the IR-To-UHF Con- Measuring The Standby Current How do we measure a standby current of only 12nA? After all, this is far below the current ranges of any digital multimeter. The procedure is to feed the supply to the circuit via a 100kΩ resistor but with a switch connected across it to allow the circuit to be powered up normally; it does draw more current at power up. Then, after a second or so when the micro has gone to sleep, the switch is opened and the voltage across the resistor is measured. For 12nA, the voltage measured across the 100kΩ resistor is 1.2mV. 66  Silicon Chip verter in the hand-held remote. With no signal present, the data output from the UHF receiver is just random noise with an amplitude of 5V. In this state, the receiver operates at maximum gain, due to its automatic gain control (AGC). When a UHF signal is received, the AGC reduces the receiver’s sensitivity so that the detected signal is essentially noise-free. This is fed to the GP5 input (pin 2) of PIC micro IC1. To determine if a signal is valid, IC1 checks for periods where the data line from the UHF receiver is at 0V for at least 8ms. This indicates that the AGC has reduced the sensitivity of the receiver and that a transmission is occurring. The 8ms periods also indicate breaks between successive bursts of 433MHz signal. IC1 drives the IR LED (LED1) and siliconchip.com.au This view shows how the IR-To-UHF Converter board is mounted and wired inside the Altronics A-1012 universal infrared remote control. The PCB assembly should also fit inside many other universal remotes. 0V +3V 4004 D1 13170151 IC1 OPTO1 4N25 1k 47k PIC12F675 ANT K 433MHz Tx MODULE 100 A C 2013 TX1 1k 1 F IR to UHF CONVERTER + 1 F – X Y TO IR LED DRIVER CIRCUIT IN REMOTE ANTENNA: 170mm LONG an Acknowledge LED (LED2) from its GP1, GP2 & GP0 outputs; ie, GP0 drives LED2, while GP1 & GP2 drive LED1. Note that the acknowledge LED does not simply follow the data signal level; it is only intended as a visible confirmation that a valid signal is being received. A second output is provided via a 3.5mm jack socket (CON2) for an external IR LED (if necessary). This LED can be wired to a 3.5mm jack plug on the end of a cable to allow the LED to be attached or mounted near to the IR receiver of the appliance(s) being operated. The GP4 input of IC1 monitors the voltage set by trimpot VR1 which is across the 5V supply rail. Its wiper voltage is converted to a digital value within IC1, allowing the IR carrier frequency to be adjusted to suit the particular infrared receiver in the appliance under IR control. The adjustment range is from 33.33kHz to 47.66kHz in 10 steps. Setting VR1 to its mid position gives 38kHz. Usually, 38kHz is satisfactory but some remotes may require a different carrier frequency to this. siliconchip.com.au Fig.4: follow this parts layout diagram to build the IR-To-UHF Converter. Power comes from the remote’s 3V supply, while the input to OPTO1 comes from the remote’s IR LED driver circuit (see Fig.2). Main Features & Specifications IR-To-UHF Converter Transmission range to UHF receiver: >30m Signal detect delay: 62μs for start and finish UHF transmitter power down: 600ms from end of signal Standby current: 12nA typical (12nA measured on prototype) Operating current: unmodified IR hand-held remote = 10mA; with UHF transmission = 12mA total UHF-To-IR Converter Valid transmission: requires 8ms minimum quieting period Acknowledge LED: 654ms time-out after a valid signal Modulation frequency adjustment: 33.33-47.66kHz in 10 steps Current consumption: 50mA during reception and transmission of an IR signal IR transmission range: typically 2m to appliance receiver Power is derived from a 9-12V DC plugpack. This is fed in via diode D1 which provides reverse polarity protection. A 78L05 3-terminal regulator then provides a 5V supply for RX1 and IC1. IR-To-UHF converter assembly Refer now to Fig.4 for the assembly details on the IR-To-UHF Converter. July 2013  67 23170151 100 F 78L05 100 F IC1 A A 220 220 Vcc DATA DATA GND VR1 10k 15107132 1k PIC12F675 1k ANT GND GND Vcc DC IN LED2 ACK. 100nF CON1 CARRIER FREQUENCY D1 4004 REG1 LED1 CON2 RX1 C 2013 UHF RECEIVER toT IR DEL RI O r evLED i e c eR F HU ANTENNA: 170mm LONG Fig.5: this parts layout diagram and the accompanying photo show the assembly details for the UHF-To-IR Converter. Trimpot VR1 sets the output IR carrier frequency and should initially set mid-way to give a frequency close to 38kHz. It’s built on a PCB coded 15107131 and measuring just 20 x 47mm. Begin by checking the PCB for any faults (rare), then start the assembly by installing the resistors and diode D1. Table 1 shows the resistor colour codes but you should also check each one using a digital multimeter. Make sure the diode is installed with the correct polarity. The two capacitors go in next, followed by IC1 and optocoupler OPTO1. Both IC1 & OPTO1 are soldered directly on the PCB since there is insufficient space in the remote control case to allow sockets to be used. Follow with the 433MHz UHF transmitter (TX1). This is installed parallel to the PCB, so its leads have to be bent down by 90° before soldering it in place. It should be stood off the PCB slightly so that it is about same height above the PCB as the ICs. Once it’s in, install the 170mm-long antenna wire. Installation The first step in the installation is to open the remote control case. For the Altronics A-1012, a screw within the battery compartment must first be removed, after which the two halves of the case can be carefully prised apart using a wide blade. It’s then just a matter of installing the power supply leads and the leads that run from the remote’s IR driver circuitry to the optocoupler. Note that the supply leads must be run around the edge of the case, so that they don’t foul other parts when the case Fig.6: these waveforms show the operation of the IR-To-UHF Converter installed in the remote control. The yellow trace shows the bursts of 38kHz applied to the IR LED. These are coupled via the optocoupler to the microcontroller which then sends pulses of the same length to turn on the 433MHz transmitter (green trace). Scope timebase speed is 500μs/div. 68  Silicon Chip is closed. If necessary, notches can be cut into any internal plastic ribs and the wires pressed into these notches. Make sure that the supply leads connect across the full 3V supply (and not just across one cell) and be sure to connect them the right way around. As shown in Fig.2, the IR LED can be driven in several different ways, depending on the remote control. This will determine how the “X” & “Y” connections from the converter are wired to the remote’s IR driver circuitry. Fig.2(a) and the photos show the connection for the Altronics A-1012 remote. You can determine how the IR LED is connected in your particular remote using a multimeter (DMM). First, set the DMM to a low ohms range, then short its leads together and Fig.7: these are the same signals as in Fig.6 but at a timebase speed 10 times slower, at 5ms/div, to show the entire data block being transmitted. Note that there is a delay of about 50μs between the 38kHz bursts and the equivalent pulse fed to the transmitter. This is processing delay in the microcontroller. siliconchip.com.au The completed board assembly clips into the integral side ribs in the UB5 plastic case. Note how the IR LED (LED1) is bent across the top of the 3.5mm jack socket. check that it shows a 0Ω reading. Clean the multimeter contacts if the reading is above 0.5Ω. Now, with the two cells removed from the remote, measure the resistance between the anode of its IR LED and the positive battery terminal. The readings are interpreted as follows: (1) a reading of about 2-3Ω means that circuit is as shown in Fig.2(a) – ie, the limiting resistor is in series between the supply and the IR LED; (2) a 0Ω reading between the anode and the positive terminal means a direct connection like that shown in Fig.2(b). If you get a high resistance reading, check the resistance between the cathode of the IR LED and the negative battery terminal. In this case, the readings indicate the following: (3) a reading of about 2-3Ω means that circuit is as shown in Fig.2(c) (4) a 0Ω reading indicates the arrangement shown in Fig.2(d). Once you’ve determined the configuration, it’s simply a matter of tracing the connection from the IR LED to its limiting resistor and then running the leads back to the “X” & “Y” connections on the converter PCB. In practice, this means that you have to take the drive from across the IR LED and its series limiting resistor. Be sure to get the connections to the remote’s drive circuit the right way around, otherwise the converter won’t work. UHF-To-IR Converter assembly The companion UHF-To-IR Converter is built on a PCB coded 15107132 Fig.8: these waveforms demonstrate the reception and conversion of the remote control’s 38kHz infrared pulses. The yellow trace shows the remote’s 38kHz signal, the green trace is the Acknowledge LED signal and the blue trace shows the infrared pulses emitted from the UHF-ToInfrared Converter. The scope timebase speed it 500μs/div. siliconchip.com.au and measuring 79 x 47mm. This clips neatly into a UB5 plastic utility box measuring 83 x 54 x 31mm and a frontpanel label (78 x 49mm) is affixed to the lid. Fig.5 shows the parts layout on the PCB. Install the resistors and diode D1 first, taking care to ensure that the latter is correctly orientated. The capacitors can then be fitted; make sure that the two 100µF electrolytics go in with the correct polarity. REG1 can then be mounted, followed by the DC socket (CON1), the 3.5mm jack socket (CON2) and trimpot VR1 (set it mid-way). That done, install the UHF receiver (RX1), making sure it goes in the right way around. Installing the LEDs Now for the two LEDs. LED1 must be mounted at full lead length (25mm) so that it can be later bent over and its lens pushed through a hole in the side of the box (above the 3.5mm socket). LED2 is mounted with the top of its lens 20mm above the PCB surface. That’s done by pushing it down onto a 15mm cardboard spacer inserted between its leads before soldering it to the PCB. Make sure the LED is orientated correctly, with its anode (longer) lead going to the pad marked “A”. Finally, complete the PCB assembly by fitting a 170mm-long antenna wire. The PCB assembly can now be completed by installing an 8-pin DIL socket for IC1 but do not plug the PIC micro in at this stage. That step comes later, Fig.9: these waveforms are the same signals as in Fig.8 but with a timebase speed 10 times faster to show more detail. Note the rounding of the trailing edges of the transmitted 38kHz IR pulses (yellow trace) from the remote control but the much cleaner signal being re-transmitted from the UHF-To-Infrared Converter (blue trace). July 2013  69 Modifying The 10-Channel Remote Control Receiver Simple changes let you install the IR receiver & the 433MHz UHF receiver at the same time for use with both IR & UHF remotes As good as it is, last month’s 10-Channel Remote Control Receiver can be even more useful when teamed with an IR remote control that’s fitted with the tiny IR-To-UHF Converter. A couple of modifications to the PCB and some revised software for the microcontroller now allows it to be used with both IR & UHF remote control signals. By JOHN CLARKE With the tiny UHF module installed in a remote, you can control the modified 10-Channel Remote Control Receiver via both IR and UHF signals. When the remote control is within line of sight, the the receiver works by relying on IR signals. However, if you are in another room or outside your home, then the link is via UHF and the operation is seamless; there’s no need to do anything to change modes. Alternatively, you could have two remotes to control the 10-Channel Remote Control Receiver, one unmodified and one with the UHF module installed. For example, the receiver unit could be in your workshop or garage (to operate the doors perhaps) and you could have the option of controlling it using an unmodified IR unit located nearby or via a modified unit with UHF from inside the house. The circuit changes required to make this possible are quite simple. The original circuit has both the IR signal from IRD1 and the UHF signal from RX1 being applied to the RB3 input of IC1. In practice, this meant that you had to choose between installing either the infrared receiver (IRD1) or the UHF receiver (RX1) and install or remove the SET link accordingly. By contrast, the revised circuit allows both IRD1 and RX1 to be installed and the micro automatically selects between them. Fig.10 shows the circuit details. As can be seen, IRD1’s signal is applied to the RB3 input, while RX1’s signal is now applied to the RB2 (SET) input. The microcontroller separately checks for signals from either path and chooses the first valid signal. after the power supply has been tested. At the other end of the case, the 3.5mm socket hole is also centred horizontally and is positioned 10.5mm down from the lip. Again, use a pilot drill to start it, then enlarge it to 6.5mm. The hole for LED1 is then drilled 3.5mm down from the lip directly above the socket hole. Drill this hole to 3mm, then drill a similar hole for LED2 about 12mm to the right. The PCB can now be clipped into the slots in the side ribs of the box (push the 3.5mm jack socket into its hole first). Once it’s in place, the two LEDs are then bent over and pushed through their respective holes in the adjacent end. Secure the assembly by fitting the nut to the jack socket. Finally, the front-panel label can be downloaded (in PDF format) from www. siliconchip.com.au (go to “Shop” and then “Panel artwork”), printed out on photo paper and affixed to the lid using silicone or some other suitable adhesive. The four corner holes for the case screws are cut out using a sharp hobby knife. Note: the panel artwork is free to subscribers or if you purchase the PCB from the SILICON CHIP Online shop, Final assembly The PCB simply clips into the integral ribs of the UB5 case. Before doing this, you need to drill holes in the case ends for the DC socket, the 3.5mm socket and the two LEDs. The DC socket hole can be drilled first. This is positioned 6.5mm down from the top lip of the base at the lefthand end and is centred horizontally. Start this hole using a small pilot drill to begin with, then carefully enlarge it to 6.5mm using a tapered reamer. 70  Silicon Chip Modifying the PCB To modify the original PCB (coded 15106131), first cut the track that leads from the DATA output of the UHF receiver (RX1) at the point where it connects to the track that runs from IRD1’s pin 1 output to pin 9 of IC1. Note that this track is on the top side of the PCB. Do not break the connection from pin 1 of IRD1 to pin 9 of IC1. That done, solder an insulated wire link under the PCB between the DATA output of RX1 and pin 8 of IC1. The SET jumper must be left out. Both IRD1 and RX1 need to be installed on the PCB for both reception modes to be available. If you only install one of these, the unused input siliconchip.com.au 100 at pin 8 or pin 9 must be tied to ground. So, if IRD1 is out of circuit, bridge pins 1 & 2 of IRD1’s pads. If RX1 is out of circuit, install the SET jumper. 100 F 16V IRD1 IR RECEIVER 10k Modified PCB 9 RB1 RB3 IR SHUNT 2 RB0 RA4 OPEN = IRD1 installed CLOSED = IRD1 out RX1 ANT RA3 Vcc 433MHz RX MODULE 3 2 Revised software Vdd MCLR 1  A modified PCB, code 15106133, is also available that includes the necessary track modifications. Fig.11 shows the parts layout for this PCB. If both IRD1 and RX1 are installed, then both the IR SHUNT and UHF SHUNT jumpers are left out. If either IRD1 or RX1 is left out, then its associated shunt jumper must be installed. 14 4 3 7 6 The revised software for the microcontroller is coded 1510613B. It must be used regardless as to whether you modify the original PCB or use the revised PCB design. Note: this software is not suitable for use with the original unmodified PCB. The new software is available for download from the SILICON CHIP website, while the revised PCB can be purchased from the SILICON CHIP Online shop at www. siliconchip.com.au The software is free to subscribers or if you purchase the PCB, otherwise a small fee applies. 1 RA2 IC1 PIC16F88 18 -I/P RA1 DATA 8 GND 11 OPEN = RX1installed CLOSED = RX1 out 10 UHF SHUNT 12 RB2 RA0 RB5 RA7 RB4 RA6 RB6 RB7 17 16 15 13 Vss 5 Fig.11 (below): the parts layout for the modified PCB. Be sure to install the relevant SHUNT jumper if its receiver is left out of circuit (see text). CODE 2 315106133 3160151 C 2013 + OUT0 + OUT4 0V +OUT9 433MHz Rx MODULE 100 1k RX1 2 1k 1 1k CODE 1k 1k Shunt when Receiver is off PCB SHUNT UHF 1k 1k 1k 1k 100 F 100 F 100nF IR LED10 + OUT8 IC3 ULN2003 1k IC2 ULN2003 +12V + OUT7 100nF D1  K + OUT6 100 F A ACK + OUT5 1k 1k REG1 7805 + OUT3 GND DATA DATA Vcc CON1 Fig.10 (above): the revised front-end circuit for the 10-Channel Remote Control Receiver. The outputs from IRD1 & RX1 are now fed to separate inputs in IC1 and the micro automatically selects between them. CON2 + OUT2 10k & CODE2 OUT = TV IN, CODE2 OUT = SAT1 OUT, CODE2 IN = SAT2 & CODE2 IN = CD PLAYER 4004 CODE1 CODE1 CODE1 CODE1 + OUT1 10-CHANNEL REVIE CEREMOTE R ET O MERECEIVER R LE N NA H C- 0 1 IC1 PIC16F88-I/P CODE 1 ACK. ANT. Vcc GND GND ANT A LED0 LED1 LED2 LED3 LED4 LED5 LED6 LED7 LED8 LED9 LED10 IRD1 Table 1: Resistor Colour Codes o o o o o No.   1   4   2   1 Value 47kΩ 1kΩ 220Ω 100Ω otherwise a small fee applies. Testing To test the unit, first check that IC1 has not been installed. That done, apply power and check there is 5V between pins 1 & 8 of the IC socket. If siliconchip.com.au 4-Band Code (1%) yellow violet orange brown brown black red brown red red brown brown brown black brown brown not, check the supply polarity and that D1 and REG1 are correctly orientated. Assuming you do get 5V, switch off and install IC1 with its notched end towards the adjacent 100nF capacitor. Now reapply power and check that the red acknowledge LED flashes when the 5-Band Code (1%) yellow violet black red brown brown black black brown brown red red black black brown brown black black black brown remote control buttons are pressed. Note, if it does not work the 100Ω resistor to the opto-coupler may need to be switched out; try 47Ω or if that doesn’t work, you can go as low as 22Ω. The next step is to set the universal remote control so that it produces the July 2013  71 INNER CONDUCTOR SOLDERED TO TIP 3.5mm MONO PLUG SHIELD BRAID SOLDERED TO SLEEVE SINGLE CORE SHIELDED CABLE INNER CONDUCTOR TO ANODE IR LED A SHIELD BRAID TO CATHODE Making An IR LED Extension Cable Depending on how your gear is arranged, you may also want to make up a cable with a 3.5mm jack plug at one end and an external IR LED at the other. Fig.12 shows the details.You will need to use a suitable length of single-core shielded cable, while the LED leads should be insulated Fig.12: here’s how to make an IR LED extension cable if you need one. from each other using heatshrink tubing. A larger piece of heatshrink can then be used to cover the end of the cable, both LED leads and part of the lens. Par t s Lis t IR-To-UHF Converter 1 infrared remote control (eg, Altronics A-1012) 1 double-sided PCB, code 15107131, 20mm x 47mm 1 433MHz transmitter (Jaycar ZW3100, Altronics Z 6900) (TX1) 1 170mm length of yellow light duty hook-up wire 1 200mm-length red hook-up wire 1 200mm-length green hook-up wire 1 200mm-length blue hook-up wire Semiconductors 1 PIC12F675-I/P programmed with 1510713A.hex (IC1) 1 4N25 or 4N28 optocoupler (OPTO1) 1 1N4004 1A diode (D1) Capacitors 2 1µF monolithic ceramic (MMC) Resistors (0.25W, 1%) 1 47kΩ 1 100Ω 2 1kΩ UHF-To-IR Converter 1 double-sided PCB, code 15107132, 79 x 47mm 1 UB5 box, 83 x 54 x 31mm 1 front panel label, 78 x 49mm 72  Silicon Chip K 1 433MHz receiver (Jaycar ZW3102, Altronics Z6905A) (TX1) 1 PCB-mount 2.5mm DC socket 1 3.5mm PCB-mount switched jack socket 1 DIL8 IC socket 1 170mm-length of light-duty hookup wire 1 10kΩ miniature horizontal trimpot (VR1) Semiconductors 1 PIC12F675-I/P programmed with 1510713B.hex (IC1) 1 78L05 regulator (REG1) 1 1N4004 1A diode (D1) 1 3mm IR LED (LED1) 1 3mm red LED (LED2) Capacitors 2 100µF 16V PC electrolytic 1 100nF MKT polyester Resistors (0.25W, 1%) 2 1kΩ 2 220Ω Optional 1 3.5mm mono jack plug 1 1m length single core screened cable 1 3mm IR LED 1 100mm length 3mm-diameter heatshrink tubing correct code for your appliance. That done, test it without the UHF-To-IR Converter (ie, turn the converter off) first to ensure the appliance can be controlled using IR signals only. Once that works correctly, the unit can be tested with the UHF-To-IR Converter unit. Note that the converter’s IR LED should be pointed in the general direction of the appliance to be controlled. To test it, power up the UHF-To-IR Converter, cover the IR LED on the remote with a finger and check that the appliance can be controlled via the UHF radio link. If it doesn’t work, adjust VR1 as you operate the remote control until the appliance responds. Usually, setting VR1 mid-way (corresponding to a carrier frequency of 38kHz) will be suitable. Once it’s operating correctly, try using the remote to control the appliance from another room. You should get a free-air range of 30 metres of more but the range will be less than this inside a house, depending on any obstacles (walls, etc) between the remote and the UHF-To-IR Converter. Finally, note that the IR receivers in many appliances are so sensitive that they will respond to IR signals that are bounced off the walls or the ceiling of the room. So experiment before going to the trouble of making up the extension cable if you can’t aim the IR LED in the UHF-To-IR Converter directly SC towards the appliance. siliconchip.com.au