Monday, February 11, 2008

poojalooba_cow: 1 Electronics: 0

On Friday, I built a wireless microphone and interfaced it with my computer. I haven't had a chance to blog about it until now, though. I'm quite proud of my success, even though it's essentially just shorting out a wireless phone base and hooking the short into the computer input port. My other, smaller projects include a wired computer microphone and a sustain pedal for my digital piano keyboard, but this is the first semi-difficult electronics project that I've succeeded with, and I'll be keeping score from now on.

I had to pull apart the phone and the base station, first off. Then I had to find a power cord that would put out 9VDC (Volts Direct Current) of power and close to 350 mA (milliAmps). I finally found one that gave off 9VDC and 210 mA, which was close enough to get it to run (800 mA at 9VDC just made sparks and smelled like things burning...) Sorry if this sounds complicated or confusing to you, but it's the only way I can adequately explain my project.

Since I'm way too cheap to go buy a wireless computer microphone ($100), I then proceeded to find the audio output on the base station using the scientific method Trial and Error. I short-circuited across random solder beads on the base station with a screwdriver until I heard a click come from the speaker on the phone unit. I got the first group on my first try. I then tested it by feeding audio from a CD player into the two beads I found. Ta-da! Weezer's Beverly Hills came out loud and clear from the speaker of the phone. Now my microphone could be two-way. I could play audio through my computer into the base unit, which would then transmit it to wherever the phone unit happened to be, and I would eventually be able to record what the phone unit was hearing as well.

Next I had to play music into the microphone of the phone unit and touch leads from an old pair of headphones to random solder beads until I could hear the audio coming into my headphones. This part took me considerably longer to get right, but I eventually could hear Weezer's We Are All On Drugs coming through from the phone to the base station.

Then came the tricky part. I had to find a reliable way to keep my short circuit wires in contact with the solder beads, while being able to plug in an audio source or an input jack or whatever into them so as to receive or send audio using whatever I wanted. Not having a soldering iron handy, I used the next best thing: A hot-glue gun. Hot-glue dries almost as fast as solder, and is safer if you get it on yourself. Once the wires had been hot-glued to their leads, I was ready to hook it into my computer. I used my normal wired microphone's wires, and I just changed the attachment on the end from the wired microphone to the base station (alligator clips are great that way).

Now, the moment of truth. I loaded up Audacity and started recording, then went to another room with the phone unit, turned it on, and started talking. It worked! I recorded a clip so that everyone can have proof of my accomplishment:

Here are some pictures of the microphone and the base station. They're kinda fuzzy, but I tried my best to sharpen them up in Photoshop (for the most part, I failed):

Both units together:

The base unit:

The wireless unit. Note the stylish lack of plastic casing, even though it is just a normal cordless phone (plastic casings are
sooo last year):

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