27220 Parallax Inc, 27220 Datasheet - Page 69

• Manufacturer Part Number: 27220
• Description: BOOK STAMPWORKS
• Manufacturer: Parallax Inc

Specifications of 27220

• Accessory Type: Booklet
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• For Use With/related Products: StampWorks
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Not applicable / Not applicable

Using 7-Segment LED Displays · Page 59
Using 7-Segment LED Displays
As you look around and notice devices that use them, you’ll see that LEDs come in all
manner of shape, size, and color. Early on, LED manufacturers found that they could
package seven rectilinear-shaped LEDs in a Figure-8 pattern and when specific
groups of LEDs were lit, the display could be any of the decimal digits and even a
few alpha characters. We call these packaged groups of LEDs 7-segment displays.
In order to simplify wiring, 7-segment LED displays have a common internal
connection; the LEDs used on the PDB are common-cathode, that is, the cathodes of
the LEDs within the display are connected together and that connection must be
made low (connected to Vss) in order to light any of the LEDs in the package. The
diagram below shows the connections of a common-cathode LED display in relation
to the current-limiting resistors on the PDB.
Note that the PDB has five, 7-segment, common-cathode LED modules, and the
terminal marked “A” in the “SEGMENTS” section is connected to the A-segment LED
in all five modules.
In the experiments that follow we will learn how to get the most out of 7-segment
displays.