Driving display devices including 7 segment, LCD parallel display units.
In this tutorial I show you how to connect a 7 segment display to an Arduino board. For a tutorial showing how to drive 4 or 8 digit displays see (Arduino multiple digit, 7 segment display tutorial). Firstly, we must know what type of display we have as there are two possible forms, common cathode and common anode. If the display is common cathode, then the LOWER voltage side is common, if the display is common anode, then the HIGHER voltage side is common.
If you've got a 7 segment display but are not sure if it is common anode or common cathode, then you need to check the polarity of the display. This is easily done with a low voltage supply (9V or less) from a battery, bench PSU or Arduino board. Firstly and before anything else, connect a 1K resistor between the common pin and the battery. This will avoid potential damage to the LED's in the display.
Measuring voltage from an analog input. Following on from the previous example ( example for driving 7 segment LED displays ). we now build on the same circuit to make a simple voltage meter. Additional requirements: Potentiometer of at least 10Kohms. In order to measure voltage, we need to use an Arduino board analog input. Usually these are marked separately as “analog in”. We are going to use a potentiometer to adjust the voltage at the analog input.
On the previous page covering single digit displays, we dealt with driving one 7-segment digit. On this page we’ll use a multi-digit display and assume 4 digits. Just like single devices, multi-digit 7-segment displays have connections for A-G, DP and common, but they have a common pin for each digit, with one set of A-G and DP pins that are shared. So for a 4 digit display there will be four common pins.
In this article I describe how to wire a 20x4 character display to an Arduino. I'm assuming you are using a regular 5V 8bit Arduino, if this is not the case this article will not work for you as you'll need voltage level converters. Most character based LCD displays use the same wiring, but I can't guarantee that all will be the same. If your display is the same it will look like the diagrams on this page and will have 16 pins.