Magnavox NA383 Digital Convertor Box Remote

Device description by David DiPaola

Background:

Due to the limited usable space in the radio frequency spectrum, the government has recently mandated that broadcast television be switched from the archaic NTSC analog standard to the new digital standard. The switch was made so that a large block of frequencies previously allocated to terrestrial television broadcasts could be sold to private companies to further aid the development of nationwide wireless networks. But, there is a problem: millions of people in the U.S. rely on analog broadcasts on their analog television sets. This is where our convertor box comes in. It allows old analog televisions to receive the new digital broadcasts over the air using their existing television and antenna system. In order to control this box conveniently, we’ve added an infra-red remote control to our system, allowing customers to operate the box from a distance of up to 20 feet.

Definition and Functionality:

An infra-red remote (commonly abbreviated to “remote” or “clicker”) is a device that reads button presses and serializes them over an infra-red beam, which is received by the unit it controls and the unit acts accordingly.

General Description:

The remote is about 5 inches long, 2 ½ inches wide and at its thickest ¾ of an inch thick. We’ve decided to use black plastic for the case in order to give the remote a similar appearance to other remotes that would be commonly found in this environment. The buttons are rubberized in order to provide reliability and a good tactile response, as well as minimize cost and complexity. Some of the key buttons, such as the channel up/down and the power buttons are colored in order

to differentiate them for further ease of use.

Figure 1: A view of the whole remote

Figure 2: A view of the top half of the plastic shell

Figure 3: The bottom half of the plastic shell

Figure 4: The key membrane

Figure 5: A description of the key mechanism

Figure 6: The printed circuit board

Part Listing:

-Plastic shell

-Holds components in an ergonomic case

-Black in color, made of lightly textured plastic

-About 5 inches by 2 ½ inches by ¾ of an inch

-Weighs about 7 grams

-Manufactured using injection molding

-Membrane

-Contains conductive pads which allow button presses to be made

-Black color, with blue channel buttons and a red power button

-About 4 inches by 2 inches by ½ of an inch

-Weighs about 3 grams

-Manufactured by injection molding

-Printed Circuit Board

-Contains all button contacts and electronic components

-Greenish in color, contact pads are black. Made of copper on a

fiberglass base with a layer of non-conductive insulation over the top

- About 4 inches by 2 inches by ½ of an inch

-Weights about 5 grams

-Manufactured at remote location, using wave soldering to secure

electronic components

Assembly:

Laying down the bottom of the case, with the open cavity facing upwards, lay the PCB down so that it fits into the lower half of the case. Then lay the membrane over the appropriate parts of the printed circuit board. Then lay the top half of the case so that is fits snugly with the bottom half. Screw together all three screws on the backside and snap in the battery cover.

Explanation of Function:

When the user presses a button, a connection is bridged, which sends a small amount of electricity to the microcontroller. The microcontroller then pulses the infra-red LED with information that corresponds to the button’s function. The infra-red beam is received by the converter box, and the appropriate action is executed.