Another Cellphone TV-B-Gone mod
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Another Cellphone TV-B-Gone mod

by stephanie on Sat Feb 04, 2012 7:26 pm

Last week I was out at lunch with my sister and showed her the TV-B-Gone -- and what it did.

We had a bit of a giggle but she pointed out that it looked just a bit too suspicious, what with being an exposed circuitboard and all. I'd taken the Adafruit kit and just stuck it ontop of a 900mAh LiPo battery with some sugru:

So I remembered reading about someone using a cellphone as a 'shell' for it, and thought that this would be nicely inconspicuous. I had a relatively new Nokia that looked good, small and innocent, and that I was not using. So I decided to gut it. There wasn't too much salvagable inside but I did keep the speakers, screen, and a few other parts for future projects.

It also had its own 3.7v 800mAh Li-Po battery which I figured was a good power source so I kept that in place. This meant I couldn't make huge changes to the frame of the phone as it still had to fit the battery in its normal spot.

Using a new Adafruit TV-B-Gone kit, I basically cut the circuit board in half and put the top half with the LEDs and the transistors into the top of the cellphone, where the phone had stored its speaker, earpiece, et cetera. The phone had a window for a built-in flashlight and originally I was just going to use that, and restrict the device to the two long-range LEDs. Then partway through the build I changed my mind and widened the hole up further and added the two wide-angle LEDs.

My first thought was to build out the rest of the circuit dead-bug style, to squeeze the components in wherever I could. However I dropped that idea because it would make it nigh-impossible for me to update the firmware later. I decided to go with SMD components, but being useless with PCB layout I grabbed an off-the-shelf widget that had an SMD ATTiny85 already in place. (SF AVR stick)

(Finished the build, now charging the battery.)

I cut that to fit, depopulated the parts I didn't need/want, and wired it in. Finally, I wanted to be able to recharge the battery in-situ so I added a mini-USB Li-Po charger - which also had to be cut to fit. I accidentally cut a necessary trace, but it was fixable by soldering directly to the remaining part of the trace. (next time look at both sides of the PCB before you cut it in half! hehe)

To make the screen appear 'off' (instead of just showing through to the wires and circuits) I painted the inside of the plastic screen cover with three coats of dark nailpolish. And finally, to fit the cover back on, I had to trim some of the rubber from the back of the keypad.

(Looks innocent enough. Just dial 4 to shut off the televisions!)

The finished device is self-contained, with a mini-usb jack at the bottom for recharging, and fits easily and inconspicuously in the hand.

Just dial "4" to turn off the TV and the "keypad backlight" will blink to let you know it's working.


p.s. here's the back of it, with the outer cover removed to show the battery.
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Re: Another Cellphone TV-B-Gone mod

by adafruit on Sun Feb 05, 2012 8:00 pm

nice work! not suspicious at all ;)

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Please be positive and constructive with your questions and comments.