My Raspberry Pi</a> arrived a couple of weeks
ago and I've been working on turning it into a mini-audio server to
connect to the home stereo in the living room.</p>
As part of the project I'd like to drive an analog VU
meter</a> from the sound signal.</p>
This week my (enthusiastic!) wife and I played around with attaching
some basic electronics to the GPIO ports so that we could get more
comfortable the Raspberry Pi. Our electronics knowledge is more than a
little rusty but surprisingly everything we tried worked first go.</p>
On the first night we attached a LED in line with a resistor directly to
a GPIO port and were able to programmatically turn it on and off. Easily
done.</p>
Then we took that a little further by using a transistor to switch the
LED from the Pi's 5V power supply. This is a better option because the
circuit can be arranged so that a minimal current is pulled from the
GPIO pin but a higher current can be put through the LED to give a nice
bright light. The amount of current you can put through the GPIO pins
without damaging the Pi is limited so this is a safer option (although
not strictly needed for a single LED). There's an excellent
page</a>
on elinux.org which explains this arrangment.</p>
Here's the result (sorry about the dodgy video quality):</p>
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My Raspberry Pi arrived a couple of weeks ago and I've been working on turning it into a mini-audio server to connect to the home stereo in the living room. As part of the project I'd like to drive an analog VU meter from the sound signal. This week my (enthusiastic!) wife and I played around with attaching some basic electronics to the GPIO ports so that we could get more comfortable…
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