Step 2: Wire Voltage Regulator

Now, wire up your voltage regulator, the center pole of the cigarette lighter is the positive (12v) and the outside is the ground. So, according to the schematic that came with your voltage regulator (or the LM317 diagram), connect the center pole to the positive input of the voltage regulator (see closeup images), and the outside connector (ground/negative) to the resistor connected to the adjust pin (see closeup image).

As mentioned earlier, here is the formula for determining what resistors you need for a an LM317 regulator:
(Voltage out) = 1.25 * (1 + (R2/R1))

Since we want apprx. 3v out I decided to use R2 = 150ohm and R1 = 100ohm which results in:
(Vout) = 1.25 * (1 + (150/100)) = 1.25 * 2.5 = 3.125v

3.125v is a little more than needed, but not enough to matter.
I'll leave the math to you if you need a different output (system of two equations anyone?)

Pick two wires that run through the cable to the phone and hi-jack them for your own uses : )
I picked the red and black wires, just because that makes sense for power and ground. Solder your chosen power wire to the output of your voltage regulator (see closeup image), and your chosen ground wire to the ground/outer pole you already connected to the voltage regulator. Make sure you cover any metal surfaces that may contact others with electrical tape.

Now, on the other end of the charge cable, snip off the old charger cable end and strip the wires you chose for your power and ground.
The later model Tunecasts have an external supply input, aswell as the option to select exactly what frequency you want to use, so the TC1 is pretty much junk in my opinion, the TC3 is good, but has an annoying habit of cutting out with quiet music, but the TC2 is the best for modding, as you can take out the audio cutout nonsense, you can add an external antenna and power it from an external supply... :)
No argument from me. The TC1 pictures here was a little old when I decided to tear it apart. I should get a newer one, I just have a hard time tossing out something that works for me... though when I'm in big cities and local stations start cutting into all 4 channels, I get pretty angry. -darc
I have this same model. Here's how I addressed the swamp-out issue (other signals interfering with mine).<br /> I opened the case, turned my home stereo on one channel, and carefully touched the end of a 10 ft. (3 m.) piece of thin (about 24 ga.) insulated wire to different places inside 'til I found the place which gave me the best signal level on the stereo. Turns out to be one of the battery leads. I then cut a little notch in the case for the wire to exit and tucked it behind the inside edge trim of my windshield (my radio antenna is on the passenger-side front fender). No more swamp-outs when driving downtown. :)<br /> I would have done an 'ible on it, but it's simple enough. Besides I plan on making a much better signal coupler later at the same time I make a semi-permanent installation with the power adapter.<br />
That's why I like my TC3 (when it's not cutting out my music when it goes quiet), you get the full range from about 89-107.9Mhz, so you can scan your local frequencies on your radio the pick the one with the most static... :) You can get a cheap TC2 or TC3 on ebay, and then sell off your old TC1 on ebay (if you can reverse the modification safely), there's always someone after an FM transmitter, as some places have little or no radio coverage, either through distance or topography, so they can utilise one of the TC1's 4 frequencies... :)
I just got one of this last week. But yesterday I found it's onsale here $15 off.<br/><a rel="nofollow" href="http://www.pricebat.ca/Belkin-MP3-CD-MD-FM-Transmitter-3-5mm-Plug-2-AAA-Batteries.p_10049603/">http://www.pricebat.ca/Belkin-MP3-CD-MD-FM-Transmitter-3-5mm-Plug-2-AAA-Batteries.p_10049603/</a><br/>...oooooops<br/>
sweet idea, I modded mine just like that cept I added a decent antenna
Did you have the same model transmitter as me? The instructables I looked at for adding a better antenna noted that it wouldn't work with this model, but I haven't actually taken it apart and examined the circuit board to confirm that claim.
it does wonders for mine ( the same 1 in the pix)
I've been contemplating something similar, although, looking at re-using a car cell phone charger for the power source. Figure this could save me the trouble of building the voltage regulator and stuffing it inside the cigar adapter. I have an old one around that I think puts out 3v.
That would save some time and money, the one I had (that I used to house the voltage reg) output 5v so it was no good : ( It was an old off-brand Nokia charger, probably from around 2001.

About This Instructable




Bio: Just a geek with a soldering iron...
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