Hear Those Ohms: An Audible Multimeter for the Blind (PART 2)

I already posted awhile back about my audible multimeter project for the blind – for those thinking of doing something similar, here’s some more details:

mutimeter for blind shot 1

The finished device hooked up to meter. On the right side is the power button; on the left is the ‘speak’ button. The front has the Arduino with the Adafruit wave shield on top. At back is the 9v battery. The middle is two pieces of (poorly) carved balsa, which hold everything in place. The larger piece is glued down, and prevents the Arduino from shifting back, as well as providing a ‘notch’ for the battery to rest; the smaller removable piece has a notch in it to keep the Arduino from shifting up (the lid in turn keeps the block in place). As I said previously, balsa is the poor man’s 3D printer…

multimeter for blind shot 2

From this angle, you can see the notches in each balsa piece better, as well as the ‘helper’ for the battery. The balsa notch was a bit loose in this one, so I inserted a folded piece of corrugated plastic, which stays in place with a thumbtack and the backs of the two switches. My second version didn’t need the plastic sheet, as I whittled the battery notch better.

multimeter for blind shot 3

Near the upright removable block you can see the DuPont cables plugged into the Arduino via the Wave Shield. Using these connectors made the device easier to assemble, since I could solder everything together and test it outside of the box, then assemble and plug it together afterwards (notice the graphic on the lid in the first picture; that’s the plug layout for the Arduino in case any of them should come loose). The separate wiring ‘harnesses’ I had to solder ended up being the battery/power switch, the speech button, and the RS232 signal cable.

multimeter for blind shot 4

One last shot, showing the memory card for the audio, and at the far side, the notch for the RS232 cable. Putting a knot in the cable just before the case’s hole made it a poor-man’s strain relief – hopefully!

All in all, the project was quite interesting. It gave me some practice in project building – especially soldering, since the Wave shield was my first ever soldering kit project. And while a bit rough, the important thing is that it works – and opens the door to my friend once again tinkering with all things electronic…

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