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Altronics M Article by Tim Blythman W e described the original Mega Box Arduino Prototyping System in our December 2017 issue (siliconchip.com.au/Article/10902). Then later, in February 2018, we used it to create an improved version of our Arduino Music Player (siliconchip. com.au/Article/10976). In case you missed those articles, the Mega Box allows you to plug in an Arduino board and up to two shields. It provides many extra useful functions like an LCD screen, illuminated pushbuttons, a rotary encoder, relays etc and it all fits into a plastic ‘half rack’ instrument case which comes pre-cut with all the holes needed in the front and rear panels. The result is a very neat package which can be programmed in the same way as any other Arduino device. It saves you a lot of effort in putting together the parts you need to make a slick Arduino project. It solves a big problem that Arduino has; while you can easily build a project by stacking an Arduino board with some shields, then running jumper wires to other modules and parts, the result is an unholy, tangled mess which looks very unprofessional. But you can build the same project 38 Silicon Chip just as easily (if not more so) using the Mega Box, and the result is neat, slick and professional looking. So what’s not to like? This updated version adds several useful new features, which we’ll describe shortly. The front panel of the case carries Altronics’ “Inventa” branding, which is their home brand for Arduino-related products. You might have seen the article we published in October on Home Automation using two Arduino wallplates, also from the Inventa range (siliconchip.com.au/Article/12023). As well as describing the new Mega Box V2 (also referred to as the Mega Box Mark II in some places), we’re also going to provide full instructions for building it. Our instructions expand on those provided with the kit, which should make construction easier, and also help you figure out how to use it. For example, the Altronics instructions we received did not provide a list of parts supplied in the kit (which should be rectified in later versions), so we’re publishing a full parts list at the end of the article in case you need it. Once you’ve built the Mega Box V2, you will need the Arduino IDE (integrated development environment) software to program it. The latest verAustralia’s electronics magazine sion can be downloaded for free from: http://siliconchip.com.au/link/aatq We’re currently using version 1.8.5. While the Mega Box will work with an Arduino Uno or similar form factor board, to take full advantage of its capabilities, you really need an Arduino Mega or similar. Mega Box V2 features From the outside, the Mega Box V2 looks almost the same as the original; it’s built into the same case (Altronics Cat H4996), so it’s the same size when finished, although the front panel has been rearranged. There are also some new connections at the rear of the case. Inside is where most of the changes have occurred. The biggest of these is the addition of a second set of shield headers, meaning that a second shield can now be fitted. You could fit more than one shield with the original Mega Box, but only if you left the lid off! That sort of defeats the purpose of using a nice case like this. There are now five relays instead of two. These are rated at 2A/30V DC, and a ULN2003 Darlington transistor array now controls all the relays. They are Altronics Cat S4128C double-pole relays, but only one set of contacts is siliconchip.com.au Mega Box V2 An Arduino Prototyping System Movie sequels are rarely as good as the original, but that is not the case here. The Altronics Mega Box V2 has more of everything you might need to prototype your next Arduino project. Features • Five 2A/30V DC relays controlled by a ULN2003 Darlington transistor array • A rotary encoder • 160-pad prototyping area • Eight opto-isolated digital input signals rated up to ±24V • An IR receiver for use with a remote control • Fits two Arduino shields minimum, or however many you can stack. • Four illuminated momentary pushbuttons • 16 x 2 character LCD with PWM backlight • Uses an Arduino Mega, Uno, or similar broken out from each to a set of pluggable terminal blocks. Apart from the relay contacts, the extra connections on the rear of the case are for up to eight opto-isolated digital input signals. These feed into a pair of LTV-847 quad opto-isolators before being buffered by a pair of 74HC14 quad Schmitt trigger inverters. These could be useful to interface with external circuitry running from a different (and possibly isolated) power supply. As for the original Mega Box, all the peripheral connections are brought out to header sockets on the PCB. Nothing is committed to any pins on the main processor board, giving complete flexibility in the way everything is wired. This is apparent in the Mega Box V2 circuit diagram, which is shown in Figs.1 & 2. Note the extensive use of headers for connecting the various optional sections of the circuit back to the Arduino’s I/O pins. The Mega Box V2 also includes better support for 3.3V Arduino boards and more flexible front panel button wiring options. But it’s the extra shield slot, added relays and isolated inputs that really set it apart. The only reduction in features with the newer board is the prototyping siliconchip.com.au area, which has dropped from 210 pads down to 160 pads, although this could easily be compensated for by fitting a prototyping shield in the extra shield slot. On the front panel, it has four illuminated momentary pushbuttons, an IR receiver, a rotary encoder and a 16x2 character LCD. Inside the case are a pair of user-defined LEDs which can also be connected by jumper wires to any I/O pin. LED3 inside the case is connected to D13 of the Arduino module header, as is common these days. Jumper JP1 is provided to allow one pin of each front panel switch to be connected to GND, so that you only need to run a single jumper wire back to an Arduino pin to sense presses of that button. JP2 (shown in Fig.2) allows each end of the eight opto-isolated inputs to be connected or disconnected from the external terminal blocks. Note how many of the components are powered from the Arduino module’s IOREF pin. This means that they are powered from 5V if it’s a 5V micro, or 3.3V if it’s a 3.3V micro, so their inputs and outputs can be connected directly to Arduino I/O pins. Four fiveway headers are provided to make it easy for you to tap into the 3.3V, 5V, Australia’s electronics magazine GND and Vin (external DC input) rails. Because the reset button on the Arduino processor board is covered up when the board is installed, a separate tactile switch is provided (S1). The LCD module itself plugs into CON5, with all of its pins brought out to CON4, so that they can be connected to the Arduino (or elsewhere) as needed. Trimpot VR1 provides display contrast adjustment while CON19 and the first inverter in IC8 give the option for software backlight control. Construction As mentioned above, instructions are provided with the kit, and these are certainly sufficient for building it, which is not an overly difficult task. However, we thought that beginners would appreciate a bit more detail, so we’ve prepared a PCB overlay diagram to guide you, shown in Fig.3. Keep in mind that the following instructions, along with those supplied by Altronics, are for building the Mega Box V2 as a prototyping platform. But if you have a particular task in mind, you could consider eliminating some or all of the sockets and soldering hookup wires directly to the pads on the board. December 2019  39 40 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.1: this diagram shows most of the circuitry in the Mega Box V2; the rest (for the new opto-isolated inputs) is in Fig.2. It is dominated by the connections between the main Arduino module (MODULE 1) and the two shield sockets. There is also an extra set of sockets for all the Arduino pins, including the Arduino Mega-specific pins, so that you can connect them to other components such as LEDs, buttons etc via jumper leads. siliconchip.com.au Australia’s electronics magazine December 2019  41 Fig.2: the eight opto-isolated inputs are between pin pairs on pluggable terminal blocks CON1 and CON2. These can withstand up to ±24V, with +1.5-24V corresponding to ‘on’. The outputs at the collector pins of IC1 and IC2 are inverted, and these are then buffered and re-inverted by hex inverters IC3 & IC4. The eight single-ended isolated signals are available for sensing at CON6. This could give a neater end result, as you could cut the wires to the minimum lengths required, rather than using fixed-length jumper leads. We won’t describe that approach in detail, but it’s worth keeping in mind. There is also less hassle in not needing to fit as many headers. Obviously, this is a much more permanent and less easily changed approach. So we only suggest it for confident constructors. If you’re doing that, you could also save time by leaving off any components you won’t be using. By the way, the kit doesn’t come with any jumper wires. It’s designed mainly with male-male jumpers in mind. So you might want to pick up a pack of these when you purchase the kit, such as Altronics Cat P1016 (65 pieces, each approximately 160mm long). You might also find Altronics Cat P1017 handy, as it includes 30 male/ female and 30 female/female jumpers, some of which may be required (depending on your application). If you are going to use the Mega Box as a prototyping platform, we suggest fitting all the components, as it will 42 Silicon Chip be much harder to do this later. This is mainly because some components, particularly the headers, can be difficult to hold in place while soldering if added after taller components have already been mounted on the board. To make it easier to solder the components to the PCB, the instructions generally proceed in order of lowest to highest profile components, meaning that when the board is inverted, the components you are fitting are held in place by your bench surface. The right-angle header socket for the LCD is the lowest-profile part, so we recommend fitting it first. But it’s best to solder the LCD's header on first, so that you can plug this into the PCB socket before soldering it. This allows you to check that the LCD will sit perpendicular to the main PCB before fixing the header socket in place. Note that the PCB silkscreen shows trimpot VR3 overlapping with the LCD header, but in reality, VR3 is much smaller than indicated, so there is no collision. Proceed now by fitting the resistors, followed by diodes D1-D8, the IC sockets, pushbutton S1, the relays and the single trimpot VR1. Rather than trying Australia’s electronics magazine to place many parts on the PCB and then solder them all at once, we suggest that you just fit a few at a time (or one at a time). When it comes to fitting the resistors, note that the 330W resistor on the PCB shown in the Altronics instructions has been replaced with a wire link here. That’s because the 330W value results in a very dim LCD backlight. A wire link (one is supplied) is acceptable but may severely shorten the backlight lifespan due to high current, meaning a lower-value resistor like 33-47W would be better. Later versions of the kit will probably be supplied with such a resistor. Also, note that some 1kW resistors on the board need a 0.25W rating while some have a 0.6W rating. All the 0.6W resistors are mounted next to JP2, and they are marked as being 0.6W types in Fig.3. This allows up to 24V to be applied to the opto-isolated inputs. The next job is probably the most time-consuming: fitting all the headers. Some of them are supplied in long strips and will need to be snapped or cut to length. For the regular pin headers, usually you can snap these easily by holding one side with pliers and siliconchip.com.au This is how the completed Mega Box V2 PCB looks. We have fitted all the jumper shunts as most user applications will also need to do so. The manual also suggests using some short lengths of wire to brace the LCD in position, which we haven’t done (yet). then using a second pair of pliers, or your other hand, to snap off the unwanted length. But for the header sockets, it’s a more involved process as you will need to use side cutters or similar to cut down the middle of one pin (sacrificing it), then clean up the remaining plastic housing of that pin with a small file to give you a neat socket of the right length. Luckily, this is not required for the 6-way, 8-way or 10-way sockets as these are supplied ready to install. When it comes to installation, if you have an Arduino and some shields (which surely you do, if you’re building the Mega Box V2), you can use them as jigs to plug the headers/sockets into before feeding them all into the board and soldering them all at once. This helps keep everything nice and square, and prevents the headers from moving about as you’re mounting them. But that only works for the headers for the Arduino and its shields. The remainder will need to be installed one at a time. Check Fig.3, the photo above and the Altronics instruction sheet to see which headers should be male and which female. If you want to do a neat job, it’s best to solder just one pin of each header first, then flip the board over and check that it’s straight before soldering the siliconchip.com.au other(s). If it isn’t correctly aligned, you can re-heat the solder joint and carefully nudge it into position. Many of the female sockets scattered around the board are designed so that you can use a male-male jumper leads to connect the two points. So if you know what you’re doing and have plenty of female-female jumper leads on hand, you could substitute regular pin headers there. But if you aren’t sure, we suggest fitting them as Altronics have indicated, and as we have shown here. Once the headers are in place, it’s a good time to fit the single electrolytic capacitor and the three LEDs. These are all polarised; the capacitor’s longer lead goes towards the + sign on the PCB, while the stripe on its can indi- cates the negative side. Similarly, the LEDs have a longer lead which goes into the pad marked “A” in Fig.3, while the flat on the lens indicates the negative lead (cathode). While Altronics suggest that LED1 should be green and LED2 plus LED3 be red, we fitted the green LED for LED3 and red for LED1 and LED2. Ultimately, it’s up to you. These LEDs are not visible with the lid on the case anyway, so they are most useful for debugging. Now attach the four pushbuttons (S2-S5), the rotary encoder and the IR receiver along the front edge of the PCB. Take a moment to ensure that they are square and straight before soldering; these are some of the few components visible from outside the case. The Mega Box V2 does well to hide its Arduino interior. Only those in the know would suspect that the DC jack and USB socket are part of an Arduino Mega board. The knockout panels above the screw terminals can be used to make connections to either or both of the shields fitted, if required. Australia’s electronics magazine December 2019  43 Now plug the five ICs into their sockets. Their footprints are marked with their designations, so it is easy to check that the correct IC is being installed in the correct socket. As usual, make sure that their pin 1 dot or notch goes towards the notched end of the socket. This is also a good time to plug the LCD screen into CON4. It sits on top of the PCB, at right-angles. Four solder pads are provided in front of and behind the LCD. You can solder tinned copper wire ‘hoops’ between these pads (along the dashed red lines) to help hold the LCD firmly in place, although we didn’t bother, as the socket seemed to do a reasonable job holding it to our unit. Final assembly Fig.3: this diagram shows the recommended location and type of all components on the board. As mentioned in the text, depending on how you plan to use it, some components could be left off, and some connections could be made via wires soldered directly to pads on the board rather than via headers. You should also fit the 16 jumper shunts to the optoisolator headers (near the rear of the PCB) and four jumper shunts to the pushbutton headers (near the front). We can’t see any reason for not fit44 Silicon Chip ting the former from the start, and you’ll most likely want the latter in place too, to make it easier to detect a button press from a micro pin (in combination with an internal pin pull-up current). Australia’s electronics magazine Before testing our newly assembled Mega Box V2, we decided to mount it in the supplied enclosure. Although not mentioned in the instructions, we fitted the supplied rubber feet to the enclosure first. They prevent the unit from sliding around on the bench. The supplied instructions also suggest fitting the front of the case now, but we found it easier to leave it off initially, as it gets in the way of plugging jumper leads into the sockets near the front of the PCB. In this state, the unit is well set up for testing and prototyping. To complete the assembly (as you would do after finalising your software and internal wiring), the front and rear case parts are fitted and secured with the included countersunk screws. Once the front panel is in place, you can attach RE1’s knob. You might find it easier to screw in the countersunk screws before installing the panels. This ensures that the threads cut in the plastic by the screws are tapped straight and square. Also be aware that you need to unplug the pluggable terminal blocks from the rear of the unit before attaching the rear panel. You can plug them back in once you’ve done that. The partial knock-outs in the rear panel are optional and need only be removed if you are using a shield which is too long to fit inside the enclosure, or needs extra wire connections to go to the outside world. For example, these could be used to feed through an Ethernet cable to plug into an Ethernet shield. siliconchip.com.au Naturally, the final step is to fit the top panel. For subsequent testing and debugging, simply remove this panel to gain access to the Mega Box internals. We found this case very easy to work with. Testing it and trying it out The sample sketch can be downloaded from: siliconchip.com.au/ link/aauv It requires two external libraries to work; a third library (for the LCD) is included with recent versions of the Arduino IDE. So make sure yours is up-to-date (see the link in the intro). As the Mega Box V2 instructions note, practically all the remaining functions provided by the board can be accessed by reading from and writing to digital pins, with simple calls to digitalRead() and digitalWrite(). The two libraries used by the sample code are for infrared reception and decoding the pulses from the rotary encoder. These can be installed using the IDE’s Library Manager. They can be found using the search terms “irremote” and “encoder”. To use this sample sketch, you need an Arduino Mega and 14 malemale jumper leads. You will find that you have to push pretty hard to plug in the Mega; there are around 80 pins that you need to force into their sockets. To test the infrared receiver, you’ll also need an Altronics A1012 universal remote control programmed to code 089, or another universal remote using a similar Philips TV profile. The demo sketch describes the wiring connections that are assumed in the code; see the comments at the top of the sketch. If you only have an Arduino Uno or similar, substitute pins A0-A5 for pins D14-D19. It may even be possible to use other boards like the Leonardo, but you will have to figure out the differing pin mapping. It may be easiest (and possibly necessary) to change the pin assignments near the start of the sketch to suit the board you are using. Open the sketch, ensure that the correct board (Uno or Mega) and serial port are selected in the Tools → Board and Tools → Port menus respectively, then click Upload. If you can’t see anything on the LCD, you may need to adjust contrast potentiometer VR1. If you see solid dark blocks on the LCD, try rotating VR1 clockwise; othsiliconchip.com.au Parts List – Altronics Mega Box V2 1 plastic half-rack case with custom cut front and rear panels, feet and screws [H4996] 1 double-sided PCB, coded K9670A, 198 x 115mm 1 16x2 alphanumeric LCD [Z7013] 3 40-way female header sockets [P5390] 1 20-way right-angle female header socket [P5392] 1 2x40-way female header socket [P5394] 2 40-pin male headers [P5430] 2 2x40-pin male headers [P5410] 2 6-way female headers [P5374] 10 8-way female headers [P5375] 3 10-way female headers [P5376] 20 jumper shunts/shorting blocks (for JP1 & JP2) [P5450] 2 8-way right-angle pluggable terminal blocks (CON1,CON2) [P2678, P2658] 1 9-way right-angle pluggable terminal block (CON3) [P2679, P2659] 1 6-way right-angle pluggable terminal block (CON7) [P2676, P2656] 1 4.3mm vertical tactile pushbutton switch (S1) [S1120] 4 PCB-mount right-angle pushbutton switches with integral LEDs (S2-S5) [S1190 (red) or S1192 (green)] 5 5V DC coil, 2A DPDT telecom relays (RLY1-RLY5) [S4128C] 1 PCB-mount right-angle rotary encoder switch (grey code) (RE1) [S3350] 1 47uF 16V electrolytic capacitor [R5102] 5 M3 x 6mm plastic tapping screws (for mounting PCB in case) 1 10.5mm diameter, 12mm long black aluminium 18T spline knob (for RE1) 3 16-pin dual-wipe IC sockets (for IC1, IC2 & IC8) [P0565] 2 14-pin dual-wipe IC sockets (for IC3, IC4) [P0560] 1 length of tinned copper wire 1 length of solder Semiconductors 2 LTV-847 quad transistor output optocouplers, DIP-16 (IC1,IC2) 2 74HC14 hex inverters, DIP-14 (IC3,IC4) [Z8514] 1 ULN2003 Darlington array IC, DIP-16 (IC8) [Z3000] 1 3-pin 3.3V/5V infrared receiver/decoder (IRD1) [Z1611A] 1 green 5mm LED (LED1) [Z0801] 2 red 5mm LEDs (LED2,LED3) [Z0800] 8 1N4004 400V 1A diodes (D1-D8) [Z0109] Resistors (all 1/4W, 1% metal film) 12 10kW 7 1kW 8 1kW 0.6W 1 330W*not used, see text 1 47W 1 0W (link) 1 10kW mini horizontal trimpot [R2480B] 1 Universal remote control [Altronics A1012 or similar] is recommended. erwise, turn VR1 anti-clockwise. The demo is quite basic. Buttons on the remote will toggle the LEDs on the pushbuttons on the Mega Box. The rotary encoder will change the displayed number of the LCD and change the backlight brightness. To do much more, you will have to write your own code. Summary The Mega Box V2 does everything the original Mega Box could do and more. It now supports two shields, has five relays and eight opto-isolated inputs too. And most importantly, as Australia’s electronics magazine we said in the intro, it turns a messy prototype into a slick, professionallooking unit. One minor quibble we have with the Mega Box V2 design is that we would have preferred to have the pushbuttons and rotary encoder on the right and the LCD on the left. This would make the unit more ergonomic for right-handed individuals; after all, the majority of people are right-handed or ambidextrous. The full kit is available from Altronics (K9670A) for $120, including GST, or $210 for two at: siliconchip.com. au/link/aaxp SC December 2019  45