Switch matrix circuit
In this project, you're going to learn a matrix circuit. A matrix is made up of rows and columns. In our circuit, the rows are connected to four keys, and the columns are connected to another four keys. You'll be using this matrix circuit to light LEDs and produce sounds. How many combinations of visual and audio indications can you get?
Yes, the answer is calculated 4 x 4, or 16 types. This simple sample shows you that a matrix circuit realizes a large number combinations from small numbers of rows and columns.
When you finish wiring, make certain S1 - S8 are OFF, and slide S1 to the up (that is, ON) position. Then, press S5 - S8 one after another. LEDs 1-4 should have lit one after another.
Next, slide S1 to the down (OFF) position and S2 to the up position. Again, press S5 - S8 in order, and you'll see LEDs 5-8 light in order.
Now, slide S2 to the down (OFF) position and S3 to the up position, and once again press S5 - S8. The segments in the LED display light in clockwise order starting from the top.
And finally, slide S3 to the down (OFF) position and S4 to the up position, and press S5 - S8 in order. You should have heard four different sounds.
Perhaps, you may have checked 16 types of visual and audio indications. In the circuit, the element at the intersection of a selected row and column is activated. For example, when S1 and S5 are ON, LED 1 lights.