Computer Keyboard Matrix Circuit

When you press any particular key it completes this circuit thus enabling the processor to determine the location of the key that was pressed.

Computer keyboard matrix circuit.

5 rows x 15 columns and quickly cycle through each row column allowing you to use 2n pins only for a n x n matrix. Dave dribin has an excellent description about how these keyboards work. When we lift off the matrix take great care. A large part of this circuitry makes up the key matrix.

The key matrix is a collection of circuits under the keyboard which is broken at a specific point under every key which results in making the circuit incomplete. This way the pin set to 1 will never source current and this nearly makes it an od pin. The key matrix is a grid of circuits underneath the keys. Go back to the first matrix circuit but take into account the green overlay this time to see how this solution looks.

I verified the wiring with a multimeter but the problem was that one column driver output pin on the microcontroller gave out just 0 volts. A keyboard matrix is a great way to add buttons without using up all of your i o pins. Look carefully for any discoloration that would possibly indicate the problem area. My latest project has 64 buttons.

A keyboard matrix circuit is a design used in most electronic musical keyboards and computer keyboards in which the key switches are connected by a grid of wires similar to a diode matrix for example 16 wires arranged in 8 rows and 8 columns can connect 64 keys sufficient for a full five octaves of range 61 notes. It also controls the illumination of the caps lock num lock and scroll lock lights. By scanning these crossings a keyboard controller can determine which. In this keyboard matrix tutorial i showed how a 9 button matrix works.

Once all of the anchoring screws are removed carefully lift off the plate to expose the flexible printed circuit boards. You can read more about how that. There is a tiny flexible cap at every key position. Thus allowing it to determine which key is pressed.

Of course this isn t real od but it solves the current loop problem in a keyboard matrix. Keyboard matrix circuits contain a scanner that s constantly scanner the grid. The keyboard is a typical scanning matrix of keys so i suspected a problem with one of the column wires. In all keyboards except for capacitive models.

This same code and circuit are what i m using for a new project. If you press the h key on a keyboard matrix circuit for instance the scanner will notice the switch being activated at the intersection of the wires where the h key is located. More on that to follow. The keyboard switch matrix is wired to its inputs and it processes the incoming keystrokes and sends the results down a serial cable the keyboard cord to a receiver in the main computer box.

A keyboard is a lot like a miniature computer.