Powering FM Transmitter via USB / Other Sound Options
Does your car stereo deck have an AUX input? If so, then you’re final step is simple: connect the computer audio output to the deck input.
The stock stereo in my ’04 Civic doesn’t have an aux input, so I’ll need to follow another route.
An auxiliary input adapter is a great option if you want to spend around $80-$100, but I want to do this on-the-cheap. Otherwise I could have just bought a Zune or iPod (albeit a much less interesting venture).
I’m using a Belkin FM transmitter to broadcast the computer music over 88.7 FM (if you’re really keen, get a bumper sticker that says “ON AIR” to advertise your new station!). There’s one major problem with using this particular FM transmitter:
- It only runs with AAA batteries
The Solution: USB Power
AAA batteries produce 1.5 volts each, so we need to create a 3 V power source using the 5 V USB port. There are four wires that make up a USB cable; the standard is that the red and black cable make up the 5V / ground, and the other two are used for data communication.
Using a simple voltage divider we can drop the 5 volts down to about 3 volts.
We can superimpose our new “battery” into the FM transmitter. I could wire this all permanently, but I prefer to be able to remove it if necessary. I trimmed a K’NEX rod to the size of a AAA battery and covered the ends in aluminium foil to act as terminals. I shorted other battery terminal using a nail. Shorting isn’t bad in this case; all it’s doing is eliminating the need for a second battery. One 3 volt battery is effectively the same as two 1.5 volt batteries.
I also wrapped the FM transmitter in a loop of wire to improve the range.
One Final Note: Maintenance
Adding in new songs is not a problem. I can bring the computer back inside and remotely drag over songs/edit playlists by plugging it into the network. Another option is to use a crossover cable or wireless USB stick and directly connect to the computer with my laptop.
And, with that, the project is done! It works great, and I can forever forget about burning music CDs.
4. Powering FM Transmitter via USB / Other Sound Options