Now that you have all the necessary materials and tools, I’m going to explain how to build PIXIE’s central unit, the heart of the device and four status lights displaying CI data. Let’s start with the central unit.
A standard 400 contact points breadboard comes as a three-part set but we need only the middle part. You should gently remove whole mounting tape from its back (we’re going to replace it with Dual Lock Fastener later on) and disconnect the side parts.
Prepare some jumper wires, Particle Photon, quadruple bus buffer gates (SN74HCT125N) and connect them accordingly to the scheme:
You have to connect Photon’s data output pins (D0 - D3) to bus buffer gate’s data input pins, VCC to VIN pin and GND to Output Enable pins. Be careful and place both chips as shown on the picture. The small cutout on bus buffer gate should be pointing towards Photon.
USB Socket module
Prepare 9 pieces of foam tape ca. 12 x 18 mm size to glue sockets together with proper distance between them.
Start with first piece of tape and stick it to side of first socket, remove orange protective foil and add second layer of tape, remove foil and add layer piece. Every pair of sockets should be separated with 3 layers of tape.
Glue second socket and repeat previous steps until you have 4-sockets module.
Glue the module to the breadboard with foam tape. Make sure the USB pins are facing you and their inputs are facing up. Module should be placed on 1-6 rows of the pins and stick out the board ca. 2mm - it makes polypropylene case fit better. You can secure the module wrapping it together with breadboard several times with adhesive tape (but avoid covering USB pins!).
Solder VCC wire to upper pins of USB module as a series circuit and connect the wire to A18 pin of the breadboard. Then sorder 3rd pin of every USB Socket to individual wire and connect them to proper pin on the breadboard 1st USB to B16, 2nd to C12, 3rd to G13 and finally 4th to I16. Now we should connect sockets to the ground so solder a wire as a serial circuit to bottom pins of the sockets and then connect it to J12 pin on the breadboard.
And here we go: PIXIE’s central unit is done! Let’s move on to the status lights.
Start with unrolling 4 smartphone cables. They have both USB A plug and USB B micro plug but in this project we’re going to need only standard A plug so we should cut micro plugs off. To make PIXIE look better we have to prepare different length of cables so cut them to 30, 45, 60 and 75 cm.
Take off outer sheath of the last 1 cm of cable by cutting gently two sides of the cable with the knife, folding it with cutline and pull strong to detach it. After that take off the insulation from the four wires using wire stripper and prepare ends to soldering.
First we have to know where each wire should be solded. The easiest way to find out is to plug one USB cable to the central unit socket and check with multimeter which wire leads to VCC, DIN and GND. To do that choose test power continuity by insert one lead into pin in the socket and end of the cord. The multimeter beeps when continuity is detected.
We’ve checked two types of flat usb charge cables and in both of them wires go along the same pattern (1st to VCC, 2nd is not use, 3rd to DIN and 4th to GND) but there always is a risk that your cables would be different or you’ll decide to use other type of cable instead of flat.
I recommend to pass all the wires through little holes on the pixel ring board as you can see on the scheme and stick the cable to the middle part of the board with foam tape. It’s going to make whole links more secure.
In our next post we will make PIXIE prettier for your walls. Stay tuned for our next blog post.
- Gosia FiedorowUI Designer