Interactive Electroluminescent (EL) Device (TFCD)

In this DIY instructable, an interactive Electroluminescence (EL) object is built. The intensity of the EL light reacts upon a rotational/vertical deformation of the EL object and therefore can interact with the environment. The result is shown right here:

The basic principle consists of a photoresistor that is subjected to an ambient light and reacts upon a smooth deformation of the object. The more (ambient) light the photoresistor is exposed to, the brighter the object will light up. So, deformation of the object results in a higher brightness of EL.

With the support of this instructable you should be able to make your own interactive EL object. To get started you need to understand the basics of EL screenprinting. This will not be included in this instructable. This knowledge can be obtained with the use of the following video:

Ingredients
Screen printing materials: Silver Ink (back electrode) BariumTitanate Ink (dielectric layer) Phosphore past (luminescent layer) ITO sheet (front electrode)

Foam:
Copper tape
Photoresistor
9V AC to DC converter (e.g. WY-ELI IPSF5)
9V Battery
Wires

Tools:
Cutting machine
Drill
Soldering machine

This EL object consists of four layers: (1) Silver, (2) Barium titanate, (3) Phosphor & (4) ITO sheet. For this project we use an ITO sheet as the (flexible/transparent/conductive-) substrate for printing the materials onto.

The following images provide a picture of the mold designs (stickers) that can be cut with a computer actuated cutting machine (see figure). The dimensions of the mold designs are not added. Make sure that the Barium titanate layer is overlapping all separate layers. Therefore, the Barium titanate mold is the biggest layer and the phosphor layer is the smallest, the silver layer is positioned in between. So, Barium titanate → Biggest, Silver → Smaller, Phosphor → Smallest

When all the molds are designed it eventually has to look like an assembly of layers (blue, grey and yellow stacked).

The ITO sheet needs to be cut in a Z shape in step 3 (Last picture).

Remark: To apply the materials, it is helpful to make some visible landmarks for positioning the molds on top of the mesh. Because of the high tolerances in the design it is an important and precise task to position the material layers in a correct manner, so no interference can occur between the different layers (conductive & non-conductive).

First, take a flat ITO sheet. Put the ITO sheet underneath the mesh (see figure 1). Then start with applying the Phosphor mold on top of the mesh and stroke the Phosphor ink over the sheet. Make sure the phosphor mold is correctly positioned. The phosphor (the light emitting material) can be used as a guidance for cutting the ITO sheet in step 3. Then bake it for 10 minutes in the oven and clean the mesh with acetone.

The second part can start when the Phosphor layer is completely cured. Put the sheet again underneath the mesh and apply the Barium titanate mold on top of the mesh. Stroke the Barium titanate ink over the mold. Again, bake it for 10 minutes in the oven and clean the mesh with acetone. Repeat this step 3 times, so the Barium titanate is isolated.

The third and last bit can start when the Barium titanate is cured. Put the sheet again underneath the mesh and apply the Silver mold on top of the mesh. Stroke the silver ink over the mold. Make sure the Silver ink is completely covering the Phosphor layer and the Barium titanate layer is in between. Again, bake it for 10 minutes in the oven and clean the mesh with acetone.

After the screenprinting is done, the EL consists of all the conductive & non-conductive layers on a flat ITO sheet and is ready to emit light. Before continuing the process, make a test run. Place one contact on the ITO sheet and one on the Silver layer.

If it works, the ITO sheet is ready to be cut. This ITO sheet needs to be cut in a Z shape and some independent diagonal lines (in between the phosphor paths). Then the ITO sheet can be wrapped around, like a cylinder and the ends of the Z shape can be glued together. Stick two copper stickers on both ends of the cylinder on the inside (one on the ITO sheet and one on the Silver layer).

Now, the Electroluminescent object is finished and two small support cylinders can be drilled out of a foam material. Also, drill a hole in the centerpoint of both cylinders. On the outer shell of the cylinders a copper sticker needs to be applied as well. This enables the power to be transferred from the small cylinders onto the Electroluminescent object. Also, a wire is looped through the first small cylinders and attached on the outer shell of the second small cylinder which is positioned in the top of the EL object.

The photoresistor needs to be connected to the circuit board. Therefore, the casing of the DC to AC converter needs to be disassembled. Unscrew the back, and remove the circuit board from the casing.

To connect the photoresistor to the circuit board, the potmeter has to be removed as well. By using a soldering device, the tin on the back of the circuit board can be heated up. If the tin is heated up, the potmeter can be withdrawn from the circuit board and replaced by wires of the photoresistor (see last figure).

Next, the photoresistor needs to be connected to the circuit board, at the ends of the withdrawn potmeter. Two wires can be soldered to to circuit board of the DC to AC converter at the spot where the potmeter was connected. Use the outer soldering spots on the circuit board. The wires can be put through the hole in the foam that has been drilled previously.

Connect each end of the soldered wires to one end of the photoresistor. It does not matter which side of the photoresistor is connected to which wire. The photoresistor now can be pushed into the foam.

As a last step, all the components need to be assembled and the EL material has to be powered. As a preparation for this step, the copper was stuck to the foam at step 3. These copper ends need to be connected to the end of the power transmitter of the DC to AC converter. Again, wires are soldered to the ends of the power transmitter. The other ends of the wires are stuck to the copper ends on the foam. Now the EL material is provided with power and reacts upon the amount of light the photoresistor is exposed to.

The result should look a bit like this:

Project made by Patrick Raedts and Jurrit Heerink

Special thanks to Arthur Vogel and Arnout Franken for collaboration in the production of the EL material.