Evelands Dot Net

Next up is getting the USB cable into the button enclosure. I drilled a hole about midway up the side of the grey ring. In retrospect, I should have put the button dome on first to verify what side the cable would be coming out of. I ended up drilling it in the front of the button, when it really should be the back. Doh!

To get the cable through the hole, I desoldered the USB cable from the PCB. I then unwound the cable end from the donut shapedferrite core and fed the cable through the hole. The ferrite core gets rewound and the wires get soldered to the correct spots on the PCB. USB cables sometimes have two ground wires, one for the outside of the plug and one for the ground pin inside. In this case, both get soldered to the same point on the PCB.

With the USB cable in place, I routed the wires from the keyboard matrix side of the PCB around and made sure it would fit in the bottom compartment. Again, because the PCB from the keyboard was small I only had to remove about half of the battery compartment. With a bigger PCB, the whole thing may need to be removed. I added a drop of hot glue on each side of the PCB to help keep it in place.

To get the wires from the button PCB to the wires from the keyboard PCB in the bottom compartment requires some drilling. After attempting to route the wires around the sides, I found the grey ring sits too tightly to the base to allow this. I drilled a small hole in the center of the plastic piece that forms the top of the bottom compartment and the floor of the metal spring. I then soldered the wires from the button PCB to the keyboard matrix wires. The order on these doesn't matter as it's either closed or open. Lastly screw this down securing the keyboard PCB in the bottom compartment.

The metal spring now needs to go back in place. I routed the wires through the gap between the sides of the spring metal and the plastic of the base. I also used some hot glue to tack the wires to the underside of the button PCB in the center. This keeps them out of the way of the four legs of the button dome that protrude through the button PCB to sit on the metal spring.

The same view as above, but viewed from the side. The button PCB can now be screwed back in place on top of the plastic posts above the metal spring. Note how tacking the wires to the underside helps keep them clear of the holes in the PCB. This helps keep them out of the way of the button dome legs when the button is pressed. Before I figured this out the button worked fine, but would occasionally get stuck as the legs pinched the wires.

The button dome can then be put back in the grey ring. As long as the notches in the dome line up to the notches in the grey ring, the feet from the dome should sit in the holes in the button PCB. The entire top can then be lowered onto the base; the screw holes should only line up one way. The four screws then secure the base to the top. The sticky rubber feet should be reapplied AFTER testing.