Introduction: 14 Segment 2 Digit LED Display
Over the last several years I've tried to learn how electronic devices work, by this I mean how to get them to work with an Arduino or any controller device, this includes displays, sensors or anything else that returns a value of some sort. At the same time I am driven by my imagination to create purposeful projects I find interesting and usually outside the realm of normal. I have played with many displays, some of which I have learned to use and plenty of others I still struggle to gain a basic understanding of.
One such device is the 14 segment LED display. At first glance I was confused by the number of pins on the back of the display, this is a two digit display with only 17 pins numbered 1 through 18. As I usually do I came to Instructables to seek out any projects this community has published, under various search criteria I found little on the very basic information I needed to get it to light up and only a couple of projects.
I've searched many other web sites as well but all were too advanced for what I needed to know. The other day I dragged out my collection of LED displays and decided to manually go through the pins one by one to see if I could get it to respond. I did then by the process of trial pin by pin map the configuration of the display. I have not yet looked into which driver chip will control the characters but I have found very basic pinout usage. Hope this instructable is helpful and useful to others.
I've written this instructable with beginners in mind but there may be a morsel or two for the more advanced maker. I never turn down the opportunity to read someone else's words, they will often ring a bell. YES I DO HEAR BELLS IN MY HEAD!
I'm including a number of documents from other sites in PDF form, most of it is quite technical but for pinout purposes they should get you up and running quickly. Seeed Studio sells the ones I have so I included their data sheets and some other information. Seeed Studio says these displays are compatible with Arduino and there are driver chips available for more advanced use.
Step 2: Materials
5 volt power supply or an Arduino Uno, Mega or any other controller board with power out pins.
Medium sized bread board.
330 ohm resistors.
14 segment 2 digit display.
Step 3: Putting ItTogether
From your power source connect jumpers to the power bus on the bread board. The red line on the bread board is for positive (+) and the blue or black line is for the negative side (-). Connect these to the bus closest to the power supply then jumper the positive wire to the power bus on the other side of the board.
For test purposes insert a 330 ohm resistor from the + power bus to an unused set of pins closer to the ends of the board then connect a probe wire from the resistor. The probe can be moved to various segment pins. The ground wire (-) can be connected to pins 11 and/or 16. A ground to pin 16 will cause the segments in digit 1 to light as you touch the probe to them and pin 11 supplies ground to the segments of digit 2. The resistor is important for limiting the current through the segments, the value of the resistor is not critical but the higher the resistance the dimmer the LED segment will light.
Most of these displays are wired the same unless they are made for a particular product manufacturer.
Some displays have a reverse polarity where the 2 common pins (16 & 11) are positive (+) and the segment pins are negative (-). Just reverse the power supply connections.
The coloured image of the display has the segments identified by the lower case letters 'a' through 'm', Seeed Studio does not use the letter 'i', it looks too close to 'j',
therefore the letters to designate the segments are 'a' through 'n' skipping the letter 'I'.
The displays I have have no #3 pin but most others do, it was probably left out to cut the cost of manufacturing. Thats okay because pin 3 is not used, some other similar displays may have that pin for an additional feature.
The data sheets will give you all kinds of info you may need for a very specialized purpose, but no matter what colour the LEDs are the pinouts will be the same.
I hope this instructable helps, I purchased these displays a few years ago then didn't have time to devote mapping out the pins. Information is difficult to find and sift through, I like reading but not for hours chasing dead ends.
Enjoy and get creative. In a future instructable you will see my use for these displays.
I have included several PDF files for you to download that should help.