Exploring the Inner Mechanics of a TV Remote Control

If you're like many people, you likely grab your TV remote a couple of times a day. Let's take a closer look at what makes it tick. Here's the remote we'll be examining today:

The job of the remote control is to wait for you to press a button and then convert that press into infrared light signals that the TV can detect. When you remove the back cover of the remote, the only component visible is the printed circuit board, which houses the electronics and battery contacts.

The components here are standard for most remotes. You can spot an integrated circuit (or chip) labeled "TA11835". This chip comes in an 18 pin Dual Inline Package (or DIP). To the right, you'll find a diode, a transistor (black, with three pins), a resonator (yellow), two resistors (green), and a capacitor (dark blue). Near the battery contacts, there’s another resistor (green) and a capacitor (tan disk). In this setup, the chip detects when a button is pressed, then translates that input into a sequence similar to morse code, each key having its unique sequence. The chip then sends this signal to the transistor to amplify and strengthen the signal.

The Circuit Board

When you remove the circuit board by unscrewing it, you'll notice that it's a thin sheet of fiberglass, with copper "wires" etched across its surface. Printed circuit boards are used to assemble electronic components because they're cost-effective and easy to mass produce. Just like it's cheap to print ink on paper, it's inexpensive to "print" copper wiring onto fiberglass. Machines can also drop the necessary parts (chips, transistors, etc.) onto the fiberglass sheet and solder them in place to connect them to the copper wiring.

Upon examining the board, you'll find contact points where the buttons meet. The buttons are made from a thin, rubbery material, with each one containing a black conductive disk. When the disk touches the contact points on the circuit board, it completes the connection, allowing the chip to register the input.

At the end of the circuit board sits an infrared LED (Light Emitting Diode). Think of an LED as a tiny light bulb. While most LEDs emit visible light, the LED in a remote emits infrared light, which is invisible to the naked eye. However, certain devices, like camcorders, can detect it. If you point the remote at a camera and press a button, you'll notice the infrared light flashing on the viewfinder. The TV sensor is also capable of detecting infrared light.

The remote's basic operation works like this: You press a button, completing a specific connection. The chip detects this connection and identifies the button pressed. It then generates a signal, similar to morse code, that corresponds to that button. The transistors amplify the signal and send it to the LED, which converts the signal into infrared light. The TV's sensor picks up the infrared light and responds accordingly.

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