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# Plinth

Member Since: April 1, 2006

Country: United States

• The initial reading was 53F - is your office really that cold, did the marshmallows come from the fridge, or is the reading inaccurate at the lower temperature?

• Nifty - any future plans for an arm that will maintain relative orientation of the object picked up?

• I loved division by 9. You sum the digits and see if that's divisible by 9. The cool thing about it is that this is fully generalizable to any base. So if you have base n, you can do divisibility by n-1 by summing the digits in base n.

Divisibility by 7? Take your number in octal and sum the digits. If the resulting number is divisible by 7, the original number was divisible by 7.

When I was in 7th grade, we learned the easy division rules and the teacher had them up on a bulletin board. For 7 there was a '?'. After I had worked this method out, I made a point to find out if she was still working in the district (she was) and sent her a letter with my results.

• I was looking at the WAV trigger and my first take on it was "why \$49? Can't I do this with a Raspberry PI?" I took the time to look over the features here: http://robertsonics.com/wav-trigger/ (watch the video), and it makes it clear why - this isn't a toy. There's a 32 bit DAC (http://www.ti.com/lit/ds/symlink/pcm5100a.pdf) and an ARM doing the heavy lifting of reading from the SD card, WAV parsing, mixing, and writing to the DAC as well as the lighter work of responding to communication ports. Definitely a higher-end product.

If you compare it to the Adafruit one, you get a single sample, 12bit, and a shield that will likely max out your Arduino in resources. I'm sure it a nice product, but it is very limited compared to this.

And finally if you look at something like Elm-chan's player (http://elm-chan.org/works/sd20p/report.html), it's positively minimalist.

Nice work!

• I guitar is about -20 dB, which is not line level (0 dB), you'd need a pre-amp stage.

• As an FYI, if all you need is to accept a single coin, surplus arcade coin mechs do the job quite nicely, have a single switch output, and cost anywhere from free (ie, pulled off a dead cabinet) to cheap.

• Hooters bounce when you drop 'em!

• Why not pull in the data optically? Beam an LED onto each string and reflect onto a photo transistor the same way that optical mice work. This should eliminate all mechanical feedback...

• Projects would be great. If you're going to do a guitar tube amp, would you also do an equivalent solid state amp to compare and contrast?

• Why two transistors and four resistors when you could use 1 74LS00?

No public wish lists :(