Setting up an EL display with the EL Escudo Dos

Skill Level: Beginner

by MikeGrusin April 09, 2012 | 56 comments

Good to Glow!

EL (electroluminescent) wire (and tape and panels) are neat products that emit light when high voltage is applied to them. The plastic material glows like neon, but runs cool, is thin and flexible, and is available in a number of colors. It's great for all kinds of artistic projects, from decorating your bedroom or bike, to parade floats, to joining the Tron Guy. Our CEO Nate made an interactive Heartbeat Straitjacket for Halloween, and lead engineer Chris turned our logo into this awesome flame:

Sparkfun's EL Escudo Dos makes it easier than ever to create EL displays. This Arduino shield has connections for an EL inverter (a small module that generates high voltage AC), and provides eight EL output connectors that your Arduino sketch can turn on or off under software control. This allows you to easily create animated EL displays, signage, or whatever your imagination can come up with!

Before we go any further, here's a brief warning: EL WIRES RUN ON HIGH VOLTAGE. Don't worry, it's "only" 100V and very low current, so it's generally not dangerous. However, getting shocked is a bit unpleasant. If you're careful, there's no reason for this to happen. Unless you cut it (which you can, just insulate any exposed edges afterward), all EL wire / tape / panels safely seal the high voltage within a layer of plastic. But do keep in mind that like many of Sparkfun's products, the EL Escudo Dos is a bare board with exposed components and traces. To avoid shocks, always power down your entire circuit before plugging and unplugging connectors, and don't touch any exposed metal on the board while it's operating. For extra safety on public projects, we recommend enclosing it in a case or otherwise isolating it from curious fingers.

With that out of the way, let's get going!

Quickstart:

1. Solder stackable headers to the EL Escudo Dos.
    
2. Plug the EL Escudo Dos into the Arduino of your choice.
    
3. Attach an EL inverter to the "DC TO INVERTER" and "AC FROM INVERTER" connectors on the EL Escudo Dos. (You may need to configure the EL Escudo to ensure that the voltage coming from the "DC TO INVERTER" connector is appropriate for your inverter, see below.)
    
4. Attach your EL wire / tape / panels to the "A" through "H" output connectors.
    
5. Load the example sketch or your own code onto the Arduino.
    
6. Glow!

Parts and tools needed:

In addition to an EL Escudo Dos, you'll need some or all of the following items:

• Soldering iron
• Solder
• Safety glasses
• One set of Arduino stackable headers (2 x 6-pin, 2 x 8-pin)
• A "full sized" Arduino (Pro, Uno, Leonardo, Mega, etc.)
• An EL inverter, such as Sparkfun's  3V or 12V models (see below for advice on choosing one)
• A power supply for the Arduino and inverter (12V supply recommended, see below)
• EL wire , tape, or panels with JST connectors, as required for your project

If you'll be modifying our 12V inverter for all-in-one operation (see below), you'll also need:

• A JST pigtail
• A small Phillips screwdriver, solder wick, and flush cutters

Soldering headers to the EL Escudo Dos

To plug your EL Escudo Dos into an Arduino, you'll first need to solder stackable headers to the board. (We don't preattach these to keep retail costs down, and because many users want to wire directly to the board.) If you've never soldered before, don't worry, it's easy, although you may want to practice on something else if this is your very first time soldering.

The six and eight-pin stackable headers go into the matching groups of six and eight holes on the board. (The correct holes are surrounded by white rectangles.) The black plastic socket side of the header goes on the component (top) side of the board, and and the pins stick out the bare (bottom) side of the board. An easy way to solder these headers to the board is to insert all four headers into the board, then flip the assembly upside down and place it on a flat surface. Then you can solder the joints from the bottom (now facing up) side of the board. Don't forget to wear your safety glasses!

It's important for the headers to be soldered on straight so that they will easily plug into an Arduino, and other boards can plug into them. A good way to ensure this is to solder only one pin on each header, then check the alignment. If it's not straight, remelt the joint and quickly straighten up the header before the solder cools. Once the header is straight, finish soldering all the joints. Try not to get too much solder on the long pins that are sticking up, as these need to be clean in order to plug into the sockets on your Arduino. That wasn't so bad, was it?

Plug the EL Escudo into your Arduino, and let's keep going!

Choosing your inverter

To drive your EL wire, you'll need an EL inverter. An EL inverter takes in low-voltage DC, and boosts it to the high voltage AC (100V, 1000Hz) necessary to make EL wire glow.

SparkFun carries two inverters, a 3V version and a 12V version. The 3V version is great for battery-powered systems, but is best for small displays since it can only drive a few meters of EL wire. If you have 12V available, the 12V inverter is considerably stronger and is capable of driving dozens of feet of wire at high brightness.

3V inverter (COM-10201)	12V inverter (COM-10469)

A note about brightness: The brightness you get will depend on the strength of your inverter and the total length of EL wire you're driving. The less EL wire you're driving, the brighter it will be. This is important to remember because the EL Escudo Dos has eight output channels. If you turn on only one channel at a time, the wire connected to that channel will be bright. But if you turn on multiple channels simultaneously, the brightness of all the EL strands will decrease, because the total length of EL wire you're driving has increased. If you use a strong inverter such as our 12V model, this generally isn't a problem, even for all eight channels being on simultaneously. However, for smaller inverters such as our 3V model, you may want to plan your display so that the wires are short and you're not driving too many channels simultaneously.

Connecting the 3V inverter

BEFORE CONNECTING ANY INVERTER OR EL WIRE TO THE EL ESCUDO DOS, ENSURE THAT EVERYTHING IS POWERED OFF!

Because of its low voltage requirements, Sparkfun's 3V inverter is ideal for small, battery-operated EL displays. The 3.3V supply built into many Arduinos is not strong enough to run this inverter, so the EL Escudo Dos has its own built-in voltage regulator. The regulator comes preset to 3.3V, which is ideal for this inverter, but it can be changed to other voltages for other inverters. See the schematic for details.

3V inverter (COM-10201)

The 3V inverter has two JST connectors attached to it; a DC input (with red and black wires), and an AC output (with two black wires). To connect the inverter to the EL Escudo Dos, plug the JST connector with the red and black wires (the DC input) into the Escudo's "DC TO INVERTER" connector. Next, plug the JST connector with the two black wires (the AC output) into the Escudo's "AC FROM INVERTER" connector. That's it!

tl;dr: If you're powering your Arduino with 5V or above, you don't need to do anything more. If you're powering a 3.3V Arduino Pro with a Lipo battery, use your soldering iron to close the SJ1 solder jumper. Here's why:

The voltage regulator on the EL Escudo is connected to your Arduino's VIN pin, which is in turn connected to the raw power input to your Arduino. Depending on your Arduino and how you're powering it, this could be the power jack, the USB connector, or a battery connector.

The voltage regulator on the EL Escudo requires an input at least 1.5V above the output in order to operate. This means that the Arduino needs to be running on at least 4.8V for the regulator to be able to output 3.3V.

If you're running your inverter on less than that, such as a single-cell 3.7V Lipo battery, you can easily bypass the voltage regulator and directly connect VIN to the inverter. To do this, use your soldering iron to melt a blob of solder onto solder jumper SJ1, which is located just below the "C" in the "CAUTION HIGH VOLTAGE" label on the top side of the board. Note that when you close this jumper, you'll be sending whatever voltage is on the VIN pin directly to the "DC TO INVERTER" connector, so ensure that you're not powering your Arduino with more voltage than the inverter can handle. (The 3V inverter can take up to 4.2V, so it's safe to run on a Lipo battery, but once you make this modification, remember to not connect your Arduino to a higher-voltage supply without unplugging the inverter first!)

Connecting the 12V inverter

BEFORE CONNECTING ANY INVERTER OR EL WIRE TO THE EL ESCUDO DOS, ENSURE THAT EVERYTHING IS POWERED OFF!

If you have 12V available, or want to make the biggest, brightest display possible, Sparkfun's 12V inverter is a great choice.

12V inverter (COM-10469)

Off-the-shelf, the 12V inverter comes with a barrel plug connection for the DC input. This makes it easy to power directly from a 12V wall-wart. If you'd like to power it this way, connect the DC input to a 12V wall-wart, and connect the AC output JST connector to the Escudo's "AC FROM INVERTER" connector. That's it!

This setup works perfectly fine. But if you'd like to power both the inverter and the Arduino from a single 12V supply, you can easily modify the EL Escudo and inverter to do so. Here's how:

Step 1: getting 12V to the "DC TO INVERTER" connector

The EL Escudo Dos has a built-in voltage regulator that takes the raw voltage on the Arduino (VIN), and regulates it down for low-voltage inverters such as Sparkfun's 3V model. But since we can run both the inverter and the Arduino on 12V, we don't need that regulator any longer. We can bypass it by closing solder jumper SJ1, which is located just below the "C" in the "CAUTION HIGH VOLTAGE" label on the top side of the board. Use your soldering iron to place a blob of solder on that jumper, connecting both sides together. When you close this jumper, the VIN pin (12V) will be connected directly to the "DC TO INVERTER" connector, allowing you to power your inverter via the same 12V supply powering the Arduino.

Step 2: changing connectors on the inverter

The DC input on Sparkfun's 12V inverter has a connector that accepts a wall-wart plug. This is usually a great feature, but in this case, we'd rather have that input be a JST connector so we can hook it directly to the EL Escudo board. Never fear! We can easily hack one in.

First, open up the inverter's case. It may look like there's no way to do so, but peel off the round sticker, and you'll find a Phillips screw below it (tricky!) Remove the screw, open the case, and take out the inverter's PCB.

Next, remove the existing barrel-jack connector. Before doing so, make a note of where the red and black wires go on the PCB. (There should be "+" and "-" markings on the board, but you can't be too careful.) Heat up the solder on the bottom of the board, and pull out the wires one at a time. If the holes aren't clear when you're done, clean them out with solder wick, or melt the solder and immediately give the board a light rap on your workbench to clear out the holes. (You are wearing your safety glasses, aren't you?)

Now we'll solder in the new JST pigtail. Strip the wires a quarter-inch or so., insert one wire at a time into the proper location, and apply solder to the bottom of the board. When both wires are soldered, clip off any excess.

Before reassembling the case, it's a very good idea to mark which JST connector is the input, and which is the output, since they're now identical.

Put everything back together, plug the DC input you just made into the "DC TO INVERTER" connector, plug the AC output into the "AC FROM INVERTER" connector, and we're ready to fire things up!

Summary

Attaching EL wire, tape, etc.

This is the fun part. Plug up to eight EL wires, tapes, panels, etc. into the output channels of the EL Escudo. These are the JST connectors labeled "A" through "H" along the edge of the board.

Now is a good time to mention that JST connectors can be very tight, especially when new. If you want to unplug something from a JST connector, don't pull on the wires. A good technique is to use a pair of wire cutters to grab the plug without squeezing, and pull it out of the socket:

Heat 'em up!

The moment has finally arrived! Connect your programming connector to the Arduino / EL Escudo stack, and power it up. Remember that once the inverter is powered up, portions of the circuit will have high voltage on them, so watch your fingers. (Handling the board by the Arduino itself is a good idea. You can also wait to attach the inverter until after you've programmed the Arduino, if desired. And if you're using the 12V inverter, it has a convenient on/off/blink switch you can use to keep it powered down until everything's ready.)

Once the Arduino is powered up, load the example code. Once it's running, both the status LED on the Arduino, and the status LED on the EL Escudo should be blinking. Turn on the inverter (if it isn't already), and hopefully you'll see your EL wire blinking away!

Troubleshooting

If nothing is happening, here are some things to check:

• Are you running code that turns on that EL channel?
  • (If you're running the demo code, the status light should be blinking rapidly.)

• If you're using the 12V inverter, is the inverter's built-in power switch on?

• Power everything off, and ensure the JST connectors are fully seated.

• Power up the board, and use a multimeter to check the DC voltage at the "DC TO INVERTER" connector (you can use the holes adjacent to the connector). Is the appropriate voltage for your inverter present?

• Power up the board, and (carefully) use a multimeter to check the AC output of the inverter, at the "AC FROM INVERTER" connector (you can use the holes adjacent to the connector). The inverter must be powered on for this test, and your multimeter must be set to VAC. Are you reading in the vicinity of 100VAC?

• If your EL wire is blinking, and you think it should be steady-on, and you're using the 12V inverter, check the position of the inverter's power switch. This inverter has a built-in blinking circuit which runs if the switch is in the middle position.

If you've checked all these things and you're still having problems, please feel free to contact our Technical Support department, who will be happy to help you out.

Programming

Programming the EL Escudo Dos is very easy. No libraries are needed; controlling the output channels is as simple as turning a LED on or off. In fact, that's exactly what you're doing - inside each of the eight optotriacs on the board is an LED that is internally coupled to a light sensor on the high-voltage side. By using light to bridge the gap between the AC and DC sides of the circuit, there is complete electrical isolation, which makes the board safe and reliable.

The eight EL channels, labeled "A" through "H" on the board, are linked to digital I/O pins 2 through 9. Before using a channel, make that pin an output using the command:

pinMode(pin,OUTPUT);

To make a channel turn on, make that pin HIGH with:

digitalWrite(pin,HIGH);

To make a channel turn off, make that pin low with:

digitalWrite(pin,LOW);

It's that easy! See the example code for a basic framework to build on.

Can I dim the EL wire?

The quick answer is not really. You may be able to achieve a few dimming levels by using the analogWrite() command, but because this board uses zero-crossing triacs and there's no synchronization between the AC waveform and your Arduino's PWM, dimming isn't terribly effective. Some analog levels will produce stable dimming zones, others will produce flickering. You can't hurt the board by doing this, so feel free to experiment; you will probably find a few levels that work well, and maybe flickering is exactly the effect you're looking for. Remember that not all pins on an Arduino support PWM, so you'll be limited to "dimming" channels B, D, E, and H.

Have fun!

If you have any questions, problems or tips you'd like to share, feel free to post them in the comments below or let us know. And if you build an awesome project, we'd love to hear about it (and maybe feature it on our front page!)

Have fun with your EL Escudo Dos!
-Your friends at Sparkfun.