In the same way that we stitched the ground or negative connections of our LEDs together in Chapter 3, Sewable LEDs in Clothing, we are going to use a common ground connection for all of the negative connections of each color LED. Starting with the red LED furthest from the poppers, place your LED on it's marker on the piece of the fabric and stitch it to the fabric using a long length of conductive thread stitching through the negative connection of the LED. Continue with the same piece of conductive thread, and stitch a running stitch along the marker line on your fabric, and then use this to attach the negative connection of the next LED. Continue doing so for all the red LEDs, and finally, run your conductive thread to a female half of a popper, and stitch this to its marker on the fabric. Finish attaching the popper to the fabric by stitching the other three sides down with standard thread. Now, stitch each positive connection of your LEDs to the fabric and run a length of conductive thread to a male popper half on its marker on the fabric; again fasten the other three sides of the popper to the fabric with standard thread. You should now have your four red LEDs stitched to your piece of fabric terminating on five popper studs. Repeat the same process for your green and blue LEDs. To ensure that each LED has a sound connection to the conductive thread, place a small amount of clear nail varnish over each joint of the conductive thread. Here is a picture of my stitched LEDs over the transfer:

Before we can test our LEDs, we need to create our connection to Pi Zero. In the same way as we did in Chapter 3, Sewable LEDs in Clothing, we are going to use a piece of fabric, which will have the other halves of the poppers sewn onto, with a cable soldered to each popper, and at the other end of the cable, it will be soldered to the relevant pin on the Pi Zero. You may have noticed that we have not included a hidden pocket in this design to house the battery and the Pi Zero; this is because I am going to use cables long enough so that the Pi Zero and battery can be placed in the wearers pocket. If you would prefer to have a hidden pocket, then just follow the steps in Chapter 3, Sewable LEDs in Clothing.

Cut a length of cable for each popper stud about 50 cm in length. I am cutting three black cables for each ground connection, four red cables for the red LEDs, four blue cables for the blue LEDs, and four yellow cables for the green LEDs. Strip and tin one end of each of your cables, and then solder each cable to its corresponding popper half; male for the black cables and female for the red, blue, and yellow cables. For the black cables, be sure that the cable is soldered across the back of the popper, as shown in this picture, so that the cable does not impact on the closing of the popper. Once you are sure that the popper half, with the cable soldered to it, will securely connect to its counter-part, snip any excess cable from the popper:

When soldering red, blue, and yellow cables to the female half of the poppers, feed the cable through one of the holes of the popper from the rear, and solder it to the front of the popper half as shown here. Then, clip back any excess cable and check whether it connects soundly to its counter-part popper half:

So now that we have soldered the poppers to all of our lengths of cable, we need to attach them to their other halves, and make sure that we can identify which is which and check they are all connected securely. Lay your piece of fabric with the LEDs stitched to it out, and connect each cable to its matching popper. Ensuring that you are running the cables toward the bottom of your design, gently bend each cable so that they run in a line straight down your fabric, as shown here. You can now take a permanent marker or some correction fluid and mark each end of the cables so that you can identify each one later. I am simply placing one to four dots on each of the colored cables to indicate if it is red, blue, or green 1, 2, 3, or 4 LED that it is attached to:

Now that we have labeled our cables, we need to attach them to a piece of fabric so that we can attach and remove them in one go. In the same way we did in Chapter 3, Sewable LEDs in Clothing, cut a piece of fabric large enough to cover the poppers and the cables 2.5 times in width. Now, fold the piece of fabric in half and stitch it around one of the long sides and one of the short sides to create a pocket. Once you have stitched the three sides, turn the pocket inside-out and stitch the remaining fourth side. Now, place your stitched piece of fabric over your cables and poppers, and carefully mark the center position of each popper with a marker on your stitched piece of fabric. Now, remove your first popper and cable from the design and stitch it to your piece of fabric. To ensure that the cable does not get damaged, stitch the cable to the fabric too, as shown in this picture. Continue to stitch the remaining poppers and cables to the marks you made, ensuring they are in the correct order! As you add more cables, place a few stitches over the cables to hold them down to the fabric too:

Now that we have stitched all of our poppers and cables to our small piece of fabric, we can neaten the cables up ready to attach to our Pi Zero.