Browse this article to find out practical ways to test your Seven Segment Displays
Introduction
Last time, you were introduced to seven-segment displays through Introduction to 7-Segment Displays with Arduino. This time, you’ll find practical ways to test a seven-segment display. The ways include finding a datasheet, preparing a test circuit, and testing the seven-segment display.
Find an Appropriate or Similar Datasheet
The first step to test your seven segment displays is to find an appropriate datasheet or wiring diagram. The reason behind it is that there are several kinds of seven segment displays. There are devices with the common anode or cathode configuration. There are also types where there is multiple seven segments on one display panel. Additionally, there are also ones that have dot notations, and even a double dot used for clocks. Whatever the configuration, it’s best to find an appropriate or similar datasheet so that you’ll find it easier to test or verify it.
You may find the product number of the Seven Segment on the side of the device such as:
However, there may be times where you can’t find the equivalent number on your search engine. This is the time where you can do some sort of trial and error. But still, it’s handy to get a reference datasheet. By doing so, you can have a baseline to start with your trial-and-error task
For example, here is part number HS410561K-D30, which is a 4-bit seven-segment display with a colon used for clock purposes. Unfortunately, the wiring diagram for that exact part number cannot be found.
With this, you can search for parts with similar characteristics. Below are some examples of the search results.
It will now depend on which datasheet you want to try first. As you can see, the SMA410561KX-1 should be a closer match to the part number, even though it is a different variant. The steps can involve a trial-and-error process.
Prepare a Tester Circuit or Multimeter
Depending on your preference, you can test a seven-segment with a multimeter or a breadboard with wires, a resistor, and a power source. A breadboard with a resistor, wires, and a power source is a more universal testing setup since sometimes, a multimeter may not be enough (based on different tester models) based on our testing.
Choose a limiting resistor close to 1k or less. For the power source, you should base it on the VF (maximum forward voltage diode drop) on the datasheet. Here, the power source is arbitrarily chosen as a 3V (AA) battery source since an exact datasheet cannot be found. Below is an example VF entry on a random seven-segment datasheet.
Test the Seven Segment Display
You can now test the seven-segment display based on your reference diagram. Note the pin numbers and PIN directions. Since this is a common anode design, Vcc will be placed on the common anode pins 12, 9, 8, and 6. The other pins (which are the alphabet and DP pins) are to be grounded through a limiting resistor. Here, the only DP pins that light up is the clock DP and 3rd bit DP.
Reference your test on the alphabet legend on the seven segment and the connection diagram. For example, this is reference for the 4th bit (and other bits too).
Below is an example test of the procedure.
Lastly, try to verify all your findings. You might find that the seven segment positions are correct although the decimal point (DP) positions can vary.
With your findings, you will now be able to know which pins you should turn on, source, or sink on your driver or microcontroller pins to get your segment to work the way you want.
