EL Wire Driver

Introduction: EL Wire Driver

This is my self-contained and programmer el wire sequencer. I plan to use it in many projects, but it is currently lighting up my christmas tree.



Plus various strands of EL Wire (this is what I have pictured):

  • Drill and drill bits
  • Soldering supplies, including iron, solder, etc...
  • Screw drivers

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Step 1: Modifying the Inverter

Start by modifying the inverter itself. This inverter is designed to accept 12v from a barrel jack, but we need it to take a jst connector.

  1. Label the input and/or output so things don't get mixed up later.
  2. Remove the QC sticker and tiny screw underneath to get access to the goey insides.
  3. De-solder where the barrel jack connects to the board.
  4. Solder one of the jst tails in its place. Be sure not to mixup positive and negative.
  5. Assemble everything back together.

Step 2: Modify Sequencer

The sequencer itself needs a little modification. It comes configured for 3.3v EL inverters but the folks at SparkFun made it configurable. I chose to put a potentiometer in there to control the brightness by adjusting the output voltage.

  1. Identify the two resistors which control voltage to the inverter (labeled A and B.)
  2. Remove the two surface mount resistors.
  3. Solder a 330 ohm resistor on B.
  4. Solder the 4.7k potentiometer to A. [1]
  5. Solder some headers to the analog output and voltage ports on the bottom right.

There is an opportunity for simplification here. If you do not need control over brightness, you can skip messing around with A and B. Instead, bridge the solder jumper in the bottom left corner. This will circumvent the on-board regulator and pass Vin directly to Vout.

[1] I screwed this up big time. Not only did I destroy the solder pads, but I attached the pot backwards so left is high, right is low. On top of that, the resister values I picked only make use of 1/8th of the potentiometer range, making it very sensitive. I should have prototyped this on a breadboard before assembly.

Step 3: Add the Power Switch and Connectors

Every project needs a good power switch. This power switch has a nice clicky toggle and lights up. It is not the one listed in the parts list, but it is similar-ish. I had this one on hand already, but wanted to give you a parts list with as few venders as possible.

  1. Solder on a pair of wires to the LED pins on the switch, including a 330 ohm resister inline. Terminate it with some sort of female header so it mates with the headers you just added to the sequencer. If the switch has the LED power built in, ignore this step.

The barrel jack needs to connect both the the power switch and the sequencer. The wiring is a little confusing to explain so look at the picture.

  1. Solder the negative pin on the barrel jack to black on the jst tail.
  2. Solder the positive pin on the barrel jack to a short length of wire which will go to the power switch.
  3. Solder another short length of wire to red on the jst tail and braid it with the wire from #2.
Depending on your enclosure, you can solder the switch to the barrel jack, but I wanted to leave my options open and left it here.

Step 4: Put It All Together

There are two items left: put some holes in the chassis, and insulate the noisy inverter.

  1. Do a fit test before making any holes. It is hard to un-drill a hole.
  2. Drill holes for: barrel jack, power switch, potentiometer, and el wires. [1]

The inverter outputs a high-pitched whine when under load which is audible in a quiet room. There are a couple ways to address this (including encasing the transformer in shellac or epoxy), but I opted to pack it into some foam insulation.

  1. Find a scrap of plastic and cut it to size. It should cut the enclosure into two compartments. Be sure there are channels for running wires through it. You may need a piece for the lid as well.
  2. Epoxy the plastic in after doing a fit check (are your wires long enough?)
  3. Cut pieces of window insulation and pack them into and around the inverter. Make it tight.

All that is left is to mount the components and complete any wiring. The power switch LED goes to the V+ and Gnd header pins. Everything else is labeled on the sequencer or already attached. I chose to leave the sequencer free-floating, but you may want to tack it down if your project will be mobile. The fit is tight enough that a little hot glue would easily do the trick.

[1] I regret some of the hole placements. First, the potentiometer is way too close to the power switch and hits it. Luckily, only 1/8 of rotation does anything (see previous comment) so it all still works. A larger hole for the el wire would have been more convenient as well.
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