CIRCUITS

1. 2 milliseconds on-time 1.0 milliseconds off-time 7. 1 milliseconds on-time

27. 8 milliseconds off-time

1. 2 milliseconds on-time 1.0 milliseconds off-time 7. 1 milliseconds on-time

A B

Fig. A: On/off infrared blink sequence for JVC brand TV remote controls.

FFigig..BA::Pull wire-wrap wire through the cap’s fabric to connect the switch on top.

How TV-B-Gone Works

TV remote controls all work the same way: by transmitting coded patterns of 940nm wavelength infrared to the television’s remote control receiver, somewhat like sending Morse code with a flashlight. The receiver watches for blinking IR, and when it sees patterns it recognizes, performs the corresponding functions on the TV. To avoid accidental triggering by reflected light in the room, receivers only respond to IR light that pulses at a specific carrier frequency.

For our TV-B-Gone, we don’t care about couch-surfing functionality; all we need is the code for turning a TV off. (Because remotes have just one on/off button, this is the same as the code to turn it on, and the TV’s current state determines which new state to toggle to.)

For example, to turn off a JVC TV, you blink the pattern shown in Figure A using a carrier frequency of 54kHz. The entire sequence lasts only a tiny fraction of a second, so there’s no perceivable delay.

Different manufacturers’ IR standards vary, but they all use rapid blinking of an even faster carrier frequency. TV-B-Gone transmits the on/off button codes for most TVs, one right after the other. So it works like other remotes, but with just one button.

1. Assemble the kit.

First I built the TV-B-Gone kit itself. I already knew how to do this, but you can follow the excellent instructions at ladyada.net/make/tvbgone.

170 Make: Volume 13

2. Install the switch.

Take out the batteries and unsolder the battery leads from the board. Then bend the 4 legs of the tactile switch apart so they’re flat, and hot-glue the switch to the button on top of the cap (Figure B).

Use needlenose pliers to push some of the wire-wrap wire through the hat fabric near the button. Pull enough wire through on the underside of the hat to reach the end of the visor. Repeat using a second piece of wire, then solder the wires to 2 of the switch’s legs on the same side, clip off the other 2 legs, and cover the soldered joints with 5" heat-shrink tubing.

If you use a lighter, be careful not to place the tubing (or the hat) directly in the flame. Hold the flame just above the tubing and move it around slowly until it’s fully shrunk.

Use a needle and thread to sew the 2 wires to the inside of the hat. I used 5 loops for each, tying them off with a square knot (Figure C). Alternatively, you can also use hot glue.

Position the assembled TV-B-Gone at the edge of the visor of the hat, with the IR emitters just inside the brim, pointing outward. Cut the wires from the hat-top switch so they extend just past the switch button on the circuit board (Figure D).

3. Install the battery pack. Center the battery pack under the cap’s dome with its 2 wires facing forward, toward the visor. Hot-glue the battery pack in place, then sew (or hot-glue) its wires to follow the same paths as the switch wires.