As part of a Burning Man camp, the participants wanted some awesome matching backpack covers of dead squirrels with lit up eyes. Don't ask why they wanted this; merely be awed by the implementation. We even went them one better by adding EL wire tire tracks on the back! This instructable only shows how to make the patches, which is the interesting part. You can put a patch of this kind onto just about anything, doesn't have to be a backpack.

Because of Reasons, I didn't get a picture of the finished pack until much later when the squirrels returned, and it is Low Quality, but you can get the sense of it at least.

"Submitted by Ace Monster Toys for the Instructables Sponsorship Program"

Step 1: Tools & Materials

The main body of the patch is made out of a soft fleece, but felt would also work well. The pieces needed are a squirrel shape, a tongue shape, two X shapes for the eyes, and a large oval in the shape of the backpack or other object you'll be placing the patch on. Additionally, I used the following materials and parts:

one felt battery cover (URL)
small amount of velcro
conductive thread
two LEDs (I used through-hole but SMDs would work if you solder a bead to the leads, to sew through (URL))
a pair of magnetic purse closure snaps
EL wire (not shown in the pic)

Tools needed were:

scissors
hand needle
round nose pliers (the kind where each prong is round)
needle nose pliers (the kind where both prongs together, when closed, are round)
pins
hot glue gun
sewing machine

Step 2: LED Eye Circuit Setup

The LED eye circuit includes just the LEDs, a battery holder (for power) and a magnetic snap, used as the on/off switch. The circuit diagram is very very simple; I can get away without a current limiting resistor because the coin cell battery used is 3V and an amperage which unfortunately I forget, but which is very close to the LED's specs. A higher voltage or greater power source would mean a resistor is needed to protect the LED from burning out - there are many LED resistor calculators online if you need to use a 9V battery, or more than 2 AA cells, or something like that.

First determine the positive and negative leads on the LED. You can tell in several ways. Unless you have a very SPECIAL kind of LED, it will have a flat spot on the bottom of the casing, by the negative lead. The interior of the LED has two shaped bits of metal, one larger than the other; the larger bit is connected to the negative lead. There's a good picture of it here. If you are in doubt, take one of the coin cell batteries and hold it between the LED's legs. If it goes on, you have found the positive and negative legs (positive leg is touching the battery's positive side, negative the other). If it doesn't go on, it's the other way around (or possibly the battery or LED is dead).

Using the needle nose pliers, roll each leg of the two LEDs into a spiral next to the base, as shown in the picture. This will allow you to sew it down flat. Thread a needle with about 12-15 inches of conductive thread. You won't use all of this on the initial segments, but will use it later.

Step 3: LED Placement and Stitching

Place the LEDs where you want the eyes to go, with the positive and negative leads arranged as in the circuit diagram (negative on the left, positive on the right, in the pics). Knot your conductive thread and sew a bunch of loops through the fabric and over the right-hand LED's left-hand, negative, lead, to get a good connection. Then make some stitches through the base fabric over towards the left-hand LED's left-hand lead, as shown in the first pic. Sew loops over the left-hand LED's negative lead to attach it to the fabric, and connect it to the other LED. Remove the needle but don't cut the thread; you'll need to sew more with it in a minute. See the second pic.

Now do the same thing with the positive traces, starting with the left-hand LED and sewing to the right-hand one, so the long tail remains on the right side of the work as in the third pic.

Tip for sewing the "traces": get the conductive thread embedded under the fabric as much as possible, to minimize the possibility of short circuits.

Step 4: Tongue and Negative Trace

Arrange the work with the tongue piece underneath the LED eyes, so that the back of the eye area is supported by the tongue piece, and the tongue part is sticking out. Run a line of hot glue at the back edge of the tongue so it stays in place, but doesn't interfere with the conductive thread traces. Draw the conductive thread tails through the squirrel body piece to the bottom, if they aren't already.

Sew the negative trace (on the left side) through the tongue fabric, out to the end of the tongue where you will place one side of the magnetic snap switch. Each side of the switch consists of two parts, a snap part and a backing part. The snap part has two flat legs sticking out the back, and the backing part has two slots through which they fit. Push the snap part legs through from the front of the tongue to the back, snipping the fabric slightly if you need to (but you may not need to). Place the backing part over the legs, from the back, as in the 8th pic. On the front side, wrap the end of the conductive thread around the legs of the snap, under the snap part, several times, as shown in the 9th pic. Pull it tight enough that all the wraps are hidden under the snap. Then bend the legs of the snap down from behind using pliers to hold it firmly in place, as in pic 10. Trim excess conductive thread.

Step 5: Positive Trace and Battery Holder

Place the battery holder on the tongue where it will not be seen when the squirrel head is folded down. Using the thread tail from the positive LED leads, sew a trace down the tongue to the battery holder and stitch firmly to the positive side (the one with a little + sewn on it in these pictures). On these holders, the + is on the top, so it can still be flipped up to access the negative terminal.

Cut the thread, the next stitching must be separate. Thread the needle with another piece of conductive thread, 8-10 inches is plenty for this one.

Similarly to how the first magnetic snap half was placed, put in another half (making sure it's a coordinating half not a matching one) where the first half sits when the tongue is folded down. Wrap the non-needle end of the conductive thread around it when installing. See the pictures for this, it's clearer. Now sew the trace from the snap part to the underside of the battery and stitch it firmly to the negative terminal.

Your LED circuit is now complete. Put a coin cell battery in the holder and test it by snapping the snap closed.

Step 6: More Gluing

Pull out the glue gun and glue all the bits down:

small velcro strips to keep the battery holder closed
around the tongue edges up to the squirrel body edge
red felt X's over the LEDs

Test again just in case. You're done with the LED section of the squirrel. Take the battery out again while you continue with the tire tracks.

Step 7: Tire Track EL Wire

Before adding the EL wire, you may want to sew the squirrel body to the backing oval. This bit is pretty straightforward and I didn't take any pictures of it. You can see the stitching lines in the EL wire pictures though.

EL wire is a composite of a medium wire (20 gauge or so, it does vary some) with a phosphorus coating, a tiny outer wire in a very small gauge, and a clear plastic coating around the whole thing. You can make fairly sharp bends in it without a significant risk of damage. There are several useful instructables on dealing with it but here I will assume you have an EL wire, driver, and battery kit which is readily available in many places on and off the internet.

If you have a wire connector between the wire and the battery/driver, detach it as the weight of the driver makes it slightly annoying to work with. If it's soldered directly, though, you can manage OK. Starting with the driver/battery end, and at the part of the squirrel that will be down, pin and bend the EL wire into tire track shapes across the squirrel's back. You may need to make minor adjustments as you go along, or if your wire is too long or too short and ends in the middle of a treadmark!

Using regular, non-conductive thread in an inconspicuous color, sew 3 or 4 stitches over each corner of the EL wire shape. See the last pic for a closeup. I found a beading needle was good for this as it is really long. There is no need to make knots and cut the thread between each point; it is much more efficient to just carry the thread under the body material to the next stitching point.

Here's the front pic again, the patch on a completed pack cover - the EL wire battery pack and driver is inside, with the wire carefully sewn through the seam of the cover. Not that you can see that in this pic, alas.

Step 8: Finished

Sew your patch onto whatever you want to put it on. Here is a completed pack cover - the EL wire battery pack and driver is inside, with the wire carefully sewn through the seam of the cover.