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Flexible D i g i ta l Lighting Controller Part three – Using it with RGB LEDs – by Tim Blythman Addressable LEDs are a simple and effective way to add coloured lights to all manner of displays. They make the perfect addition to our Digital Lighting Controller. In this final instalment, we’ll show you how to use them alone or in combination with mains-powered lights as part of our new system. W e noted early in this series that addressable LEDs are now a standard part of lighting displays. They’re easy to control and being low-voltage, are very safe. So it makes sense that you should be able to use them with the new Flexible Digital Lighting Controller. In January 2020, we described an 8x8 RGB LED matrix made from addressable LEDs (see siliconchip.com. au/Article/12228). These use the WS2812 addressable LED IC, which can be found in many other forms; last month, we reviewed some of Jaycar’s range of “wearables”, which includes their Cat KM1040 RGB LED Raft Pad, based on a compatible IC. They (and other retailers) can also 90 Silicon Chip supply the same (or similar) ICs on strips and/or reels. We’re going to use these handy modules and strips for our experiments. In this article, we’ll describe several different ways to integrate addressable LEDs into a lighting project based around our Digital Lighting Controller. The first option we’ll present is an alternative ‘slave’ unit which can control sets of these addressable LEDs. The slave unit already described can control up to four mains-powered lamps. Our LED slave can instead drive up to 64 addressable LED modules, using signals from the same master units we described last month. The two different slave units (fourchannel mains and 64-channel LED) are a great way to combine mains and Australia’s electronics magazine LED lamps with the excellent sequencing software that we produced for the original Digital Lighting Controller many years ago. We’ll also describe example software for Micromites and Arduinos which can directly drive addressable LEDs at the same time as controlling one or more mains-powered slave units. If you’re happy programming a Micromite or Arduino, you can modify our sample code and build a lighting display that does precisely what you want. Addressable LED slave unit Being able to control up to 64 mains lamps using our Digital Lighting Controller makes it easy to build an insiliconchip.com.au Here’s the LED Slave Unit driving a length of Jaycar’s XC4390 addressable LED strip for testing – and found that it not only worked well . . . it looked spectacular! It would look even better strung up outside, or wrapped around a Christmas tree! credible lighting display, but there is no doubt that the cost of doing so will add up very quickly. Our LED slave allows you to strike a compromise between expense and grandeur. One of these can control up to 64 LEDs, while each mains slave unit adds another four lamps. They can be mixed and matched in any combination within the 64 addresses that exist. The addresses can be set independently, so lamps can be set to some addresses and LEDs to others. You can even set some devices to the same address, to allow simple sequences to be more impressive by controlling both lamps and LEDs. Since the addressable LEDs tend to be smaller and produce much less light than mains-powered lamps, we’ve also come up with ways to have multiple LEDs in the same strip respond to a single address, so that you can conserve the 64 available addresses. There are various options when it comes to addressable RGB LEDs to control. We tested Jaycar’s XC4390 siliconchip.com.au addressable LED strip and found it worked well. These IP65-rated 2m strips are sealed in silicone and backed with 3M adhesive tape. Each strip has 120 LEDs (one every 17mm) and is terminated at both ends with a locking plug and socket. Each end of the strip also has a pair of wires for a separate power connection, which is handy when running longer strips. There is also a prewired plug with bare leads which we connected directly to the LED slave’s screw terminals. Although not marked, the connections are red to 5V, white to ground and green for data. We should also mention Altronics Cat X3223A, which is a 5m-long strip with 300 LEDs. While we have not tested this ourselves, we expect them to be fully compatible; you could even mix and match the two. Circuit details The LED slave circuit is shown in Fig.16, overleaf. You might recognise part of the circuit from the mains slave unit; it works in much the same fashion. Australia’s electronics magazine Opto-isolator OPTO1 receives the serial data via CON3, with CON4 available to daisy-chain the signal to another slave. CON3 and CON4 are wired in parallel and are interchangeable. A 220Ω resistor limits the current through OPTO1’s LED to a suitable level, while the diode limits its reverse bias voltage. Since there are no mains voltages involved in this circuit, OPTO1 might seem unnecessary, but it prevents the formation of ground loops, which might occur depending on how the unit is wired. It also allows circuits with different grounds to be connected without problems. OPTO1 has an open-collector output, so a 1kΩ pull-up resistor brings the output of the optoisolator to 5V when its internal transistor is off. The serial data from OPTO1 goes to the UART pin (pin 5) of IC1, a PIC16F1455 microcontroller. This decodes the serial data and produces data to drive LEDs on pin 2. This signal is fed through a 390Ω resistor and along with 5V power and ground, is made December 2020  91 l l l SC Ó DIGITAL LIGHTING CONTROLLER WS2812 SLAVE Fig.16: the circuit for the LED slave unit is quite simple, and much of it is borrowed from the mains slave described in the October issue. Virtually all of the work is done by PIC micro IC1, which receives the DMX-512-like serial data at its RC5 digital input, pin 5. It then produces a signal to drive one or more WS2812B RGB LEDs from its RA5 digital output at pin 2. available at screw terminal CON5. The resistor protects the micro and LEDs from excessive current flow under fault conditions. Power for the unit is supplied via CON1, a mini USB socket. JP1 and JP2 provide option settings. CON2 is an in-circuit serial programming (ICSP) header for IC1, in case that is required. VR1 is a 10kΩ trimpot which is used to control LED brightness, by varying the voltage applied to the analog input at pin 3 (AN3) of IC1. Indicator LED2 lights up when power is applied, while LED1 lights up when serial data is supplied. Operation The serial protocol used is explained in the previous articles in this series; it is similar to DMX-512 but uses a simpler and slower serial interface. Microcontroller IC1 decodes the serial data received at pin 5 and produces data suitable for driving ad92 Silicon Chip dressable LEDs at digital output pin 2. We used a PIC16F1705 in the mains slave, as it is slightly cheaper than the PIC16F1455 and we do not need the USB peripheral in the 16F1455. However, the PIC16F1455 also has a higher maximum clock speed (48MHz vs 32MHz). We need that for this design, to ensure that the serial data can be processed and the timing-critical LED data is produced with accurate timings. Jumper header JP2 provides the same address setting feature that the DIP switches provided in the mains slave unit. Unlike that one, the LED slave unit is not limited to controlling four lamps. So one LED slave unit set to address 0 can provide control of 64 LEDs. If the address is not set to 0, then the offset is applied and the addresses ‘wrap around’. For example, if the address is set to 16, the brightness of the first LED in the chain will be set Australia’s electronics magazine by the 16th data byte, the second LED by the 17th data byte, the 48th LED by the 64th data byte, the 49th LED by the first data byte etc. JP1 controls whether each data byte controls an entire RGB LED, or the individual colour channels (red, green and blue) within each LED. When JP1 is inserted, each LED receives identical data on each of the red, green and blue channels from the data at a single address. So the LEDs will light up white with adjustable brightness. When JP1 is out, each individual red, green or blue LED element is treated as a separate channel. Thus, you can control up to 21 individual RGB LEDs in this mode. Potentiometer VR1 is used to control the brightness, but also sets some other configurations. VR1’s wiper is divided into three roughly equal sections. Within each section, the position sets a global brightness value. You might siliconchip.com.au like to reduce the overall LED brightness either because these LEDs can be too bright, or to simply limit the current needed by the supply. Each of the three sections corresponds to a different LED configuration. At the ‘lowest’ (most anti-clockwise) section, each colour channel corresponds to one LED. In the middle section, each channel corresponds to four LEDs, and in the top section, one channel corresponds to 16 LEDs. This allows more LEDs to be controlled from fewer channels. A similar effect could be had by cutting and wiring LED strips so that they are fed data in parallel, but we think this is a much simpler approach. To keep the timing tight, each LED slave unit only produces data for 64 LEDs, so in four-LED mode, only 16 channels are used, and in 16 LED mode, four channels are used. JP1, JP2 and VR1 are continuously sampled during operation, so you can tweak the controls in real-time to get a feel for how the different modes work and look. You’ll also note that we’ve wired the USB D+/D- lines to the USB socket. The software doesn’t use these pins or the USB peripheral, so we figured that they might as well be connected, in case anyone wants to modify the software so that it does use the USB function. Software Although the brightness is set by an analog voltage from a potentiometer, the addressable LEDs use all digital data, so this conversion must be done in software. To avoid the (relatively slow) multiplication that would be needed to do this ‘live’, an array in flash memory stores a table of pre-calculated values for 16 brightness levels. This reduces the processing load on the micro. The 16 brightness levels are not linear, but are roughly logarithmic, which corresponds to the human perception of brightness. The LED data takes about 2ms to produce, during which time no serial data can be received, as the micro is too busy ensuring that the LED signal is timed accurately. So we only process every second ‘update’ from the master. With our Micromite master unit, this still means an update rate around 30Hz, which is fast enough to be unnoticeable. Eagle-eyed readers may have noted that there are no pull-up resistors on JP1 or JP2 and that the PIC16F1455 does not have internal pull-ups on PORTC (which is connected to JP1 & JP2). To simulate a weak pull-up, the pin is pulsed high very briefly (around 83ns). Stray capacitance keeps the pin high unless the jumper is in place, so the jumper state can still be sensed, and the circuit is simplified. Construction The LED slave unit is built on a small PCB which is sized to fit in a UB5 Jiffy box. It measures 79 x 45mm and is coded 16110205. Refer to the PCB overlay diagram, Fig.17, to see where the components go on the board. The USB socket is the only surfacemounted part and should be fitted first. Here, some flux paste, a fine-tipped soldering iron and a magnifying glass will come in handy. Some solder braid will help if you manage to bridge any pads. Apply flux to the pads and place the USB socket on the PCB. There are small holes in the PCB to locate it accurately. Add flux to the top of the pins as well. Now load the iron’s tip with a small amount of solder. You want to be able to touch the iron to the PCB pads and allow just the right amount to run off to form the joint; the flux will encourage this. If the USB socket is firmly against the PCB, you may only need to touch the PCB pad. If that doesn’t work, carefully bring the iron to meet the socket’s pin where it sits on the pad. A fine tip will help to prevent bridges. Then solder the four connected pins; the fifth is not needed. If you bridge any pins, finish soldering the remaining pins before attempting to remove the excess. If you are confident that the pins are lined up accurately, solder the larger side tabs to secure the part mechanically. If you have solder bridges to remove, apply some flux to the area and clean the iron’s tip. Place the braid against the solder and press gently with the iron. When the braid takes up the solder, carefully draw it away with the iron. Once you are happy, you can use a flux cleaner to remove any that is left on the PCB. Follow with the resistors, checking the values as you install them; there are six resistors with four different values. Then mount the three MKT capacitors, which are identical and not polarised. The solitary diode has its cathode facing to the right – solder it in place. CON2, JP1 and JP2 are simple pin headers. In each case, it is a good idea Fig.17: fit the parts to the LED slave PCB as shown in the component overlay above and the matching same-size photo at right. CON1 is the trickiest part to fit, so do that first. CON2 is optional if you have a pre-programmed microcontroller, and CON4 is not needed if you don’t wish to connect any downstream slave units. siliconchip.com.au Australia’s electronics magazine December 2020  93 Fig.18: connecting addressable LEDs to the LED slave is straightforward. This shows Jaycar LED Raft Pads (Cat KM1040), but other addressable LEDs will also work, such as Jaycar XC4390 or Altronics X3223A strips. to solder one pin and check that the header is straight and square before soldering the remainder. For JP1 and JP2, you can temporarily fit the jumper shunts to ensure that the pins stay aligned. CON2 is only needed if you wish to program IC1 in-circuit. When mounting IC1, ensure that its pin 1 orientation matches the PCB silkscreen and overlay diagram. You can solder it directly to the board (the more reliable method) or via a socket, which is useful if you want to reprogram it out of circuit. Solder two diagonally opposite pins, then check that the IC or socket is square and flat before soldering the rest. If you are using a socket, insert the programmed IC carefully, ensuring that no pins are bent underneath. OPTO1 can be socketed too, but it does not need to be. Use the same procedure as for IC1. VR1 will only fit one way, but you may need to bend the leads to fit it. Once it has clicked into place, solder all three leads. CON3 and CON4 are the RJ45 sockets. If you plan only to use one socket, then only one needs to be fitted. This will also save you cutting a hole in the case. In any case, snap the socket into place and solder one pin to secure it. Check that it is flat and parallel to the Parts list – Digital Lighting LED slave 1 double-sided PCB coded 16110205, 79 x 45mm 1 UB5 Jiffy box 4 12mm-long M3 tapped spacers 8 M3 x 6mm panhead machine screws 1 SMD mini USB Type-B socket (CON1) 1 5-way pin header (CON2; optional, for ICSP) 2 PCB-mount RJ45 sockets (CON3,CON4) [Altronics P1448] 1 3-way 5mm pitch screw terminal (CON5) 1 2-pin header (JP1) 1 4x2-pin header (JP2) 5 jumper shunts (JP1,JP2) 1 14-pin DIL IC socket (optional; for IC1) 4 self-adhesive rubber feet Semiconductors 1 PIC16F1455-I/P microcontroller programmed with 16110205.HEX, DIP-14 (IC1) 1 green 3mm LED (LED1) 1 red 3mm LED (LED2) 1 6N137 optoisolator, DIP-8 (OPTO1) 1 1N4148 signal diode (D1) Capacitors 3 100nF MKT Resistors (all 1/4W axial 1% metal film) 1 10kΩ (brown black black red brown or brown black orange brown) 3 1kΩ (brown black black brown brown or brown black red brown) 1 390Ω (orange white black black brown or orange white brown brown) 1 220Ω (red red black black brown or red red brown brown) 1 10kΩ mini horizontal trimpot (VR1) (code 103) 94 Silicon Chip Australia’s electronics magazine silkscreen markings before soldering the remaining pins. After those are finished, install CON5. The LEDs are mounted so that their lenses go through holes in the front panel. We’ve left them to last so that you can check the mounting arrangements before soldering them in place. Fit the LEDs so that the tops of their flanges sit around 10mm from the PCB. This ensures that the flanges clear the lid when fitted, and the LEDs don’t sit too proud. LED2 (on the left) is the power LED, which should be red. The serial data LED, (LED1) is on the right and should ideally be green. Both their cathodes are to the left, which means that their longer (anode) leads are to the right. Programming Use the MPLAB X IPE (a free download) to program IC1 if it is not programmed already. Connect a PICkit 3 or PICkit 4 programmer to CON2, select PIC16F1455 as the Device, then click Apply and Connect. You may need to select “Use Low Voltage Programming mode entry” and “Power Target Circuit from Tool” from the Power menu. LED2 will light up when power is applied through the tool. Browse for the HEX file, then press “Program” and check that it was successful. Testing Before completing the assembly, it’s a good idea to test the LED slave unit. Connect a USB power supply to CON1; the power LED should illuminate. Then connect any of the master units described in parts 1 or 2 to apply a signal to the LED slave unit. LED1 should light up when a signal is received. If all is well, connect some addressable RGB LEDs; Fig.18 shows how to connect Jaycar’s RGB Island Pads. Any compatible addressable LEDs should have similar pin markings. Check that the current draw of the connected LEDs will be within the capacity of the USB supply. The contacts on most mini-USB type sockets are rated up to around 1A; this puts a hard limit on what the LED slave unit can supply (besides what the supply can actually deliver). If you have control data coming into CON3 or CON4, you should see attached LEDs illuminate. If not, check siliconchip.com.au Fig.19: the LED slave fits neatly in a UB5 Jiffy box; make the holes as shown here. The wires for the LEDs are fed through the holes on the right-hand side, so you can adjust them to suit your wiring. Fig.20: this is the lid panel artwork, which can also double as a drilling template for the LED holes. that VR1 is not wound fully anticlockwise. Preparing the enclosure The PCB mounts in the base of a UB5 Jiffy box using four threaded spacers. The box we used had four small holes marked on the base already, so we based our design around these dimensions. If your case has similar markings, that will make construction easier. Drill four holes in the base according to Fig.19. Thread an M3 machine screw through the bottom of each hole and secure with a tapped M3 spacer from above. You might like to use Nylon machine screws so that their heads also form feet for the box. Alternatively, you could fit rubber feet (screw mounting or stick-on). siliconchip.com.au Cut the remaining holes in the sides of the base of the box as shown in Fig.19. The larger holes for the RJ45 sockets are at the top edge, so they can be started by carefully making vertical cuts with a hacksaw on either side. You might be able to snap the tabs out with wide-nosed pliers or by drilling some holes to weaken it. Then straighten up the holes with a file, carefully bringing them to the required dimensions. The hole for the USB socket is a bit trickier. Start with a pair of 4mm drilled holes, then bring the holes out to size with a small file (such as a needle file). Alternatively, a single 10mm round hole will do the job, although it won’t be as elegant. Also drill the lid as shown, to suit the LEDs. Alternatively, use the lid Australia’s electronics magazine artwork (Fig.20) as a template. Now slot the PCB into place to test it fits. Guide the USB socket into place and then rotate the PCB to bring the RJ45 sockets into their slots. Rest the lid on top and ensure that the LEDs go into their holes. Remove the PCB and make any necessary adjustments. You should also drill some holes to suit the LED wires. We used 3mm holes; this should be sufficient for most cases. Re-seat the PCB and screw it down onto the spacers with the remaining M3 machine screws. The wires for the RGB LEDs can be terminated by feeding them in through the holes and screwing them into CON5. Now print the lid artwork, cut out the holes and glue it to the lid. You can download this as a PDF from the December 2020  95 Screen1: our Arduino sample code uses Adafruit’s Neopixel library to control the addressable LEDs. It’s easily downloadable via the Library Manager, as shown here. SILICON CHIP website and print it in colour. Print it onto overhead projector film (in reverse so that it appears correctly when printed on the back) or laminate a paper copy to protect it. Use neutral cure silicone to secure it to the lid, being sure to squeeze out any bubbles. We h a v e m o r e i n f o r m a t i o n about making front panel labels at siliconchip.com.au/Help/FrontPanels Fit the lid onto the base and over the LEDs, and secure with the screws supplied with the Jiffy box. to the mains slave units, depending on how you want your display to look. Multiple chains of addressable LEDs can be connected to one of our LED slave units, although we haven’t tested how many you can parallel before the signal degrades. The current drawn by the LEDs will probably be the main constraint. This could be handy for waterfall type effects, where parallel chains of LEDs can connect to a common data source, allowing for stunning effects from even a single controller. For larger displays, you might have to consider connecting an alternate supply for 5V power. Remember that you can also drive LED strips in sets of four or 16 LEDs by adjusting VR1. You could also com- Usage With JP1 fitted, each LED becomes a single channel and produces white light (equal amounts of red, green and blue). If JP1 is not inserted then each colour becomes its own channel. This reduces the number of LEDs that can be addressed, but allows for more colour options. The colour order is red, green then blue. JP2 allows the slave address to be set. It operates identically to S1 on the mains slave. Of course, since this unit can address up to 64 LEDs, it should be considered more of an offset than an address, and the address may wrap around in some cases. You can set the LED slave unit to use the same address or different addresses 96 Silicon Chip Fig.21: using an Arduino to control both addressable LEDs and lamps via our slave units is easy. This shows the Uno, but you can also use a Mega board with identical wiring. Other boards may have different pin requirements for the serial data, but just about any Arduino can be made to work. Australia’s electronics magazine siliconchip.com.au bine this feature with multiple strips in parallel. example to write your own program. Arduino and Micromite You will need to have the Arduino IDE (integrated development environment) set up to program an Arduino board to control lights (download it from siliconchip.com.au/link/aatq). We’re using version 1.8.5 of the Arduino IDE; any version since 1.8.0 should work much the same. Wire up your Arduino board to the CP2102 Interface board and RGB LEDs as shown in Fig.21. Not shown is the RJ45 lead from the socket on the CP2102 Interface PCB to the Slave units. The data connection for the LEDs passes through a 390Ω resistor to protect the two halves of the circuit from voltage differences between independent power supplies. We’re using digital output D6 to produce the addressable LED data, but the library is configurable, so this can be changed as needed. Adafruit helped make addressable LEDs popular with their “Neopixel” range of products; they also produced a library to make them easy to work with. We’re using this library to drive our LEDs, as it doesn’t work only with Ne- You can also drive addressable LEDs from an Arduino or Micromite which is also acting as a master unit for our Flexible Digital Lighting Controller. This saves you having to build any LED slaves; the master can do all the work. This means that the addressable LEDs do not take up any of the 64 addresses, so you can have even bigger displays. In terms of hardware, we’re assuming you are using at least one slave unit (mains or LED type). You will also need one of the CP2102 Interface boards described in the October issue, to allow a Micromite or Arduino board to drive multiple slaves; otherwise, you’ll be limited to controlling 2-3 slave units. And you will, of course, need either an Arduino (we’re using the Uno) or Micromite LCD BackPack (the V3 is ideal). The examples contain some simple subroutines that produce interesting patterns on both the LEDs and mains lamps. You can try changing these by altering some of the parameters, or you might like to use our code as an Arduino opixels; it can drive any WS2812Bcompatible device. Install this library by searching for “Adafruit_NeoPixel” in the Arduino Library Manager or by downloading it directly from https://github.com/adafruit/Adafruit_NeoPixel Screen1 shows the correct library to install in the Library Manager. The library comes with example code that works with addressable LEDs, but we’ve also written a demo program that combines this with data for the slave units (allowing mainspowered lamps to be controlled too). It is part of the download package for this article. Extract the sketch, open it, select the correct serial port and board type. Press “Upload” and the LEDs and lamps should spring to life. Micromite We’ve put together a similar demo for use with a Micromite; we prototyped our version on a V3 BackPack, but any Micromite variant using the PIC32MX170F256B should work with our code. The wiring diagram is seen in Fig.22. And like the Arduino master, the pins are configurable, but in this case, we have chosen to use pin 9 for the LED data and pin 10 to drive the mains slaves. As with the Arduino example, if you need more current to drive LEDs than the USB port can provide, you will need to connect another power supply. There are no libraries to download, as these are embedded in our BASIC program as CFUNCTIONs. Open the BASIC program, send it to your Micromite (using MMEdit, TeraTerm or another terminal program) and run it. Once you have confirmed that it all works, you can modify our example to suit your requirements. Conclusion Fig.22: you can also drive RGB LEDs and/or mains lamps using any Micromite with a PIC32MX170F256B chip onboard – we tested our code using a V3 BackPack, as shown here. The pins used are reconfigurable in software. siliconchip.com.au Australia’s electronics magazine Our new Flexible Digital Lighting Controller gives you lots of options, both in terms of how you arrange the lights (using LEDs, mains-powered lighting or a mixture of both) and also how you control them, using a PC, Arduino or Micromite with your own control code, or using our sequencing software. We’re looking forward to seeing what incredible displays our readers will create, using this design as a starting point! SC December 2020  97