Fullscreen HTML5Med Res (??MB)HTML4

UHF Remote Mains Switch Transmitter Designed to control the UHF Remote Mains Switch, this hand-held transmitter can operate over a 200m range. It’s based on a PIC micro and a pre-assembled transmitter module, making it easy to build and get going. By JOHN CLARKE I the UHF Remote Mains Switch in a standalone application, then you need to also build this UHF transmitter. As shown in the photos, it’s housed in a plastic case with two pushbutton switches for on/off switching. Press the On button and power is applied to the mains socket on the UHF Remote Mains Switch. Alternatively, press the Off button and the power turns off. What could be easier? The front panel also provides access to a small rotary switch. This selects one of 10 “identities” which means that the transmitter can control up to 10 separate UHF Remote Mains Switches. This rotary switch is adjusted using a small blade screwdriver. Immediately above the “On” button is a “transmit indicator” LED. This briefly lights each time a transmission is sent (ie, when ever the On or Off buttons are pressed). However, if there is an error, this LED will flash three times in a 1.5-second period. Typically, an error will be indicated if both switches are pressed simultaf you want to control 34  Silicon Chip neously or if a switch is pressed too briefly. In either case, it’s simply a matter of pressing the desired switch again to send the control signal. How it works Refer now to Fig.1 for the circuit details. As previously stated, it’s based on a PIC microcontroller (IC1) and a 433MHz transmitter module. Under normal conditions (ie, when no signal is being transmitted), no power is applied to the circuit. This means that battery usage is kept to an absolute minimum. Pressing either switch S1 (On) or switch S2 (Off) connects the battery’s positive terminal to regulator REG1 via diode D1 or D2. A 10W resistor is included between the battery and the switches to limit the initial charge current to the 10mF bypass capacitor at REG1’s input. This minimises wear on the switch contacts. As soon as power is applied to REG1’s input, its output delivers a +5V rail to pin 14 (Vdd) of IC1. As a result, the program within IC1 starts running. One of the first things it does is to check which switch was pressed and this happens after a short delay to ensure that the switch is fully closed. In operation, S1 is monitored via a 10kW resistor at the RA2 input, while S2 is monitored via a 10kW resistor at the RA4 input. The program first checks to see if S1 is closed and it does this as follows. Initially, RA2 (pin 1) is set as an output with this pin at 0V. RA2 is then set as an input and its voltage checked to see if it is still at 0V or if has been pulled to +5V. If it is at +5V, then S1 (On) is closed and the battery voltage is being applied to REG1 via diode D1. The 10kW resistor in series with RA2 is included to limit the current into this input when its internal clamping diode conducts. This diode prevents RA2 from going more than 0.6V above the +5V supply, thereby protecting this input from damage. Next, the program checks to see if S2 is closed. In this case, RA4 (pin 3) is initially held low (0V) as an output. siliconchip.com.au Q1 BC327 REG1 78L05 C E 10k D3 D1 A 10 RA1 10k 1 10k Q2 BC549 C 3 10k B 16 E 1 S3 S4 4 C 1 4 C 1 8 9A 67 BC D ➡ 23 34 5 2 C 8 012 901 ➡ COM EF 78 456 9V BATTERY 2 C 8 Vdd MCLR A S2 (OFF) 14 4 D2 S1 (ON) A 100 F 16V 100nF 10k 100nF K K K GND 10 F 16V B 1k OUT IN 2 4 8 S3 IDENTITY (0–9) 8 6 7 9 LED1 1k 18  K ANTENNA A Vcc RA2 RA0 RA4 17 DATA IC1 PIC16F88-I/P 433MHz TRANSMITTER MODULE RA7 ANT GND RB2 RB4 RB0 RB6 RB1 RB7 RB3 RB5 10 12 13 11 Vss 5 1 2 COM 4 433MHz Tx MODULE 8 ANT Vcc DATA GND S4 ENCODE (0-F) D1– D3: 1N4148 A SC  2008 LED K UHF REMOTE MAINS SWITCH TRANSMITTER 78L05 BC337, BC549 K COM B E A C IN OUT Fig.1: the transmitter circuit uses PIC microcontroller IC1 to generate a data signal whenever switch S1 (On) or S2 (Off) is pressed. This data is then fed via IC1’s RA0 output to a 433MHz transmitter module. BCD switches S3 & S4 set the identity and encode values & must be set to match settings in the UHF Remote Mains Switch. RA4 is then set as an input and its voltage checked. A high voltage means that S2 is closed and that voltage is being applied to REG1 via diode D2. Diodes D1 and D2 provide reverse polarity protection for REG1 if the battery is connected the wrong way around. They also isolate the switch actions, so that RA2 will only go high if S1 is pressed and RA4 will only go high if S2 is pressed. As well as detecting which switch was pressed, IC1’s firmware also detects whether both switches were pressed simultaneously (as indicated by a high at both RA2 & RA4). It also detects if neither switch is pressed. In the latter case, this would mean that one of the switches was pressed but then released before the program had a chance to check which switch it was. Next, the program sets RA7 (pin 16) of IC1 high and this drives the base of transistor Q2 via a 10kW resistor. As a result, Q2 turns on and supplies base current to Q1 which also turns on. As a result, supply current can now siliconchip.com.au flow through D3 and Q1 to REG1, which means that power to REG1 is maintained even if switch S1 or S2 is released. This supply latching is necessary to allow time for the on or off code to be transmitted in its entirety without supply interruption. Diode D3 is there simply to protect the circuit from reverse battery connection. RA1 (pin 18) is the transmit indicator output. This output goes low during code transmission and turns on LED1 via a 1kW resistor. However, if the program detects that both switches were pressed or if it detects that neither switch was pressed (ie, the press was too brief), the LED flashes three times to indicate an error. BCD switches Now let’s take a look at the two binary coded decimal (BCD) switches (S3 & S4) that are connected to the microcontroller. First, BCD switch S3 sets the identity. It’s connected to IC1’s RB0-RB3 inputs and individually connects these Main Features • Controls the UHF Remote Mains Switch • Up to 10 UHF Remote Mains Switch units can be controlled • • • • • • • 16 encoder selections 200m range On/off switching Handheld operation 9V battery supply Transmit indicator Transmit error indication inputs to ground when its 2, 4, 1 & 8 switches are closed respectively. Basically, S3 is arranged as a rotary switch with 10 settings ranging from 0-9. For the “0” setting, all switches are open, while and for the other numbers, different combinations of switches are open and closed. For February 2008  35 170mm OF 1mm ENAMELLED COPPER WIRE K 10 F 100 F 4148 10k ➡ BC DE 4 C 1 78 9 A 23 Q2 2 C 8 4 C 1 78 ➡ 2 C 8 456 100nF 10k 4148 45 23 6 10k D2 IC1 PIC16F88-I/P LIE ON SIDE S2 OFF 901 S4 S3 – 433MHz Tx MODULE 1k D1 10k 10k S1 ON F0 1 18020151 REG1 ANT Vcc LED1 A DATA GND RETTIMSNART WS SNIAM ETOMER 100nF + 4148 D3 10 Q1 1k 9V BATTERY CJ Fig.2: follow this diagram to install the parts on the PC board and complete the battery wiring. Note that BCD switch S3 is installed in a socket to raise it up off the PC board (see text), to make it easier to access. The view at right shows the completed PC board mounted inside the handheld case. example, a “1” position ties the RB2 input to ground. Conversely, the RB0-RB3 inputs are pulled to the +5V supply rail when their corresponding switch is open. That’s because each input has an internal pull-up resistor of about 20kW. In operation, S3’s settings can be read by microcontroller IC1 because a low voltage on one of the inputs means that its corresponding switch is closed while a high voltage means that the switch is open. BCD switch S4 sets the encode number and is monitored in a similar way. However, this switch has six extra positions labelled A-F, giving it a total of 16 positions. The settings for S3 & S4 are sent as part of the on/off code that’s fed from RA0 to the 433MHz transmitter module. Basically, the UHF transmitter transmits a modulated signal when data is applied to its data input. A ¼-wave dipole antenna is connected to the transmitter’s output. In practice, IC1’s RA0 output can generate on/off signals for up to 10 UHF Remote Mains Switches, depending on the setting of S3 (identity). Initially, a 50ms transmission is sent to set up the receiver so that it is ready to accept data. A 16ms locking signal is then sent, followed by 4-bit encode and 4-bit identity numbers. Next, an 8-bit on/off signal is sent – either a value of 162 for “On” or a value of 150 for “Off”. An 8-bit stop code with a value of 204 completes the data transmission. Once this data has been sent, IC1’s RA7 output is set low to switch off transistors Q2 & Q1. This ensures that the supply to REG1 turns off (assuming that switches S1 & S2 are both open). Resistor Colour Codes o o o o No. 4 2 1 36  Silicon Chip Value 10kW 1kW 10W 4-Band Code (1%) brown black orange brown brown black red brown brown black black brown 5-Band Code (1%) brown black black red brown brown black black brown brown brown black black gold brown siliconchip.com.au In addition, the RA1 output is taken to +5V to switch off LED1. Finally, note that there are several decoupling capacitors at the output of REG1. These filter the supply rails for IC1 and the 433MHz transmitter module. Construction The assembly is straightforward with all parts mounted on a PC board coded 10202081 and measuring 86 x 64mm. This is housed in a remote control case that measures 135 x 70 x 24mm. Fig.2 shows the parts layout. Begin by checking the PC board for any defects such as shorted tracks or breaks in the copper. That done, check the hole sizes. The four corner mounting holes should be 3mm in diameter, as should the two holes used to anchor the battery snap leads. Now for the assembly. Install the resistors first, taking care to place each in its correct position. Table 1 shows the resistor colour codes but it’s also a good idea to use a DMM to check each resistor before installing it on the board. Next, install PC stakes for the battery snap leads and for the antenna connection near the 433MHz transmitter module. That done, install diodes D1D3, REG1 and transistor Q1 & Q2. Be sure to orient the diodes and transistors correctly and don’t get Q1 & Q2 mixed up. They may look the same but Q1 is a BC337 PNP type while Q2 is a BC549 NPN transistor. The capacitors are next on the list. Note that the 100nF ceramic capacitor mounts between Q2 and the transmitter module, while the 100nF polyester capacitors is located just below IC1. In addition, the two electrolytic capacitors adjacent to REG1 need to lie on their side, to clear the lid of the case – see photo. Switches S1 & S2 can now go in. Be sure to mount these with their flat sides positioned as shown in Fig.2 (ie, towards the top edge of the PC board). That done, install an IC socket for IC1 (notched end towards REG1) but don’t install the IC at this stage. BCD switch S3 also mounts in an IC socket, so that it is raised off the board to make it easier to adjust from outside the case. One option here is to fit a cut-down DIP-8 socket, with three pins on each side. Alternatively, we’ve provided two extra holes on the PC siliconchip.com.au Parts List 1 PC board, code 10202081, 86 x 64mm 1 remote control case, 135 x 70 x 24mm 1 433MHz UHF data transmitter (Jaycar ZW-3100 or equivalent) 1 9V battery 1 18-pin DIL socket 1 6-pin DIL socket (or 8-pin) 2 click action momentary switches (S1,S2) 1 0-9 BCD DIL PC-mount switch (S3) 1 0-F BCD DIL PC-mount switch (S4) 4 M4 x 10mm screws 1 170mm length of 1mm enamelled copper wire 1 9V battery snap connector 3 PC stakes Semiconductors 1 PIC16F88-I/P microcontroller programmed with 1020208A. hex 1 BC327 PNP transistor (Q1) 1 BC549 NPN transistor (Q2) 1 78L05 5V regulator (REG1) 2 1N4148 diodes (D1-D3) 1 3mm red LED (LED1) Capacitors 1 100mF 16V PC electrolytic 1 10mF 16V PC electrolytic 1 100nF MKT polyester (code 104 or 100n) 1 100nF ceramic (code 104 or 100n) Resistors (0.25W, 1%) 5 10kW 1 10W 2 1kW board so that it will accept a standard 8-pin DIP socket. Once the socket is in place, install S3 with its orientation dot at bottom right – see Fig.2 and the photos. If you have fitted an 8-pin socket, be sure to plug S3 into the top six pins – the two pins nearest the battery terminals are unused. By contrast, BCD switch S4 mounts directly on the PC board. Once again, be sure to mount it with the correct orientation. The UHF transmitter can now be installed. This is done by first placing it in position, then bending it down so Helping to put you in Control Sensors We have a selection of sensors for monitoring your processes. Accelerometers Accelerometer Breakout boards range from +/-2G to +/10G. Available as 2 and 3 axis. From $39+GST Serial Accelerometer A 3 axis accelerometer up to +/-6g with a simple RS232 serial interface. Available as card or enclosed. From $105+GST Dual Axis Gyro This is the first dual-axis MEMs gyro available. The IDG-300 is a 3.3V IC with a smaller profile than other single axis gyros. $99+GST Proximity Switches Inductive Proximity switches in both square and tubular forms. Detection distances from 4 to 12mm. PNP and NPN outputs From $22.50+GST Photoelectric Switches These Photoelectric switches range from 0.4m to 15m. Available with PNP and NPN outputs From $44.50+GST Temperature and Humidity Industrial grade. Wall and Duct Mount. From $209+GST Pressure High quality Industrial Pressure Sensors. Range from 0-0.5 to 0 – 1500 Bar. 4-20mA Output. $399+GST Contact Ocean Controls Ph: 03 9782 5882 www.oceancontrols.com.au February 2008  37 SILICON CHIP + + On + Off + Identity UHF Remote Mains Switch Transmitter Fig.3: this full-size artwork can be used as a drilling template for the front panel. that its top edge is about 8mm above the top of the main PC board. That done, check that it is correctly oriented before soldering its pins. LED1 must be installed so that the top of its lens is 14mm above the PC board (ie, level with the switch top). Be sure to orient it with its anode lead (the longer of the two) to the left. The board assembly can now be completed by installing the antenna coil. This is made from a 170mm length of 1mm enamelled copper wire (ECW). First, cut the wire to length and scrape away about 3mm of insulation at each end, then shape the wire into a spiral by winding it around an 8mm mandril. Once that’s done, solder one end of the antenna coil to the antenna PC stake and the other end directly to the PC board. Final assembly The final assembly basically involves fitting the board inside the case. The first step is to feed the battery snap leads through from inside the battery compartment and then down through the two holes in the PC board – see Fig.2. That done, solder the leads to their respective PC stakes, taking care to ensure that the polarity is correct. Now connect the battery and check that the voltage between pins 14 & 5 of IC1’s socket is close to 5V when S1 is pressed. If this is correct, install IC1 with its notched end towards REG1. LED1 should now briefly light each time S1 or S2 is pressed. If it doesn’t, check the LED’s orientation. Assuming all is well, the PC board can now be fitted into the base. It’s secured to the four integral stand-offs using M3 x 6mm screws. That done, set the identity and encode switches to match those in the UHF Remote Mains Switch. Now check that the UHF transmitter controls the UHF Remote Mains Switch by pressing the On and Off buttons. The neon indicator below the mains socket should come on when the transmitter’s On button is pressed and go out when the Off button is pressed. If it doesn’t work, unplug the UHF Remote Mains Switch from the wall socket and check the identity and encode switch settings in the two units. If it still doesn’t work, go over the transmitter assembly carefully and check for errors. Note also that the transmitter will not operate the UHF Remote Mains Switch if they are too close to each other. The two units must be separated by at least one metre. Once everything is working, attach the lid to the transmitter case. If you are building the unit from a kit, the lid will be probably be supplied with all holes pre-punched and with a screenprinted label. If not, then you will have to drill the holes yourself. These holes can be drilled using the front panel label shown in Fig.3 as a template. You will need to drill two 10mm holes to clear the switch caps, a 3mm hole for the LED and a 9mm hole to give access to the Identity switch (note: the latter is not necessary if you intend using the transmitter with just one UHF Remote Mains Switch). By the way, it’s best to make the larger holes by first drilling small pilot holes which can then be further drilled out to about 5mm. These holes can then be carefully reamed out to their correct sizes. That done, the front-panel artwork can be downloaded from the SILICON CHIP website, printed onto photographic paper and attached to the lid using an even smear of clear silicone sealant. Alternatively, you can print a mirror image of the panel onto clear overhead projector film and attach this with the print side towards the panel, again using clear silicone sealant. That’s it – your UHF Remote Mains Switch Transmitter is now complete SC and ready for action. Looking for real performance? Completely NEW projects – the result of two years research • • • • 160 PAGES From the publ ishe rs of 23 CHAPTE Learn how engine management systems work RS Build projects to control nitrous, fuel injection and turbo boost systems Switch devices on and off on the basis of signal frequency, temperature and voltage Build test instruments to check fuel injector duty cycle, fuel mixture and brake and coolant temperatures Mail order prices: Aust. $A22.50 (incl. GST & P&P); Overseas $A26.00 via airmail. Order by phoning (02) 9939 3295 & quoting your credit card number; or fax the details to (02) 9939 2648; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. 38  Silicon Chip Intelligent turbo timer I SBN 09585 2294 9 780958 5229 -4 46 $19.80 (inc GST) NZ $22.00 (inc GST) TURBO BOOS T & nitrous fue l controllers How engin e management works siliconchip.com.au