Datasheet For Seven Segment Display - Page 1
Forum section: electronics / projects

author: bostonman
author_rank: Super Contributor
timestamp: October 24, 2022, 01:03:19 am
content: I have a seven segment display with lines in the middle of the rectangle in the shape of an asterisk. It's four digits with a colon in the middle; leading me to believe this is a time of display. On the back it has two rows of pins, one row is nine pints and the other side is eight pins.It has two lines which I thought were part numbers: SKM4C8H56P10AY and the second line is DF007 (or DFOO7).Unfortunately I haven't found a datasheet by way of these numbers.Does anyone know what these may be?

author: Nusa
author_rank: Super Contributor
timestamp: October 24, 2022, 07:08:26 am
content: If you're talking LED, 4-digit displays are typically multiplexed. You'll find a common cathode/anode (either can be had) for each digit and 8 segment lines common to all digits. The colon likely has independent pins, but its cathode/anode could be part of the multiplex. Not too hard to puzzle out the pins yourself with diode testing. Once you find one of the common pins, the segment pins and whether its cathode or anode should be quickly discovered. Here's a random but representative datasheet of such a display:https://www.sparkfun.com/datasheets/Components/LED/7-Segment/YSD-439AR6B-35.pdfedit -- I just noticed you said "in the shape of an asterisk", which means you're probably actually talking about a 4-digit 14-segment display which can do a decent job of displaying alpha letters. Still multiplexed, but the digits will be split: two common lines per digit and seven segment lines. Which also explains why you have so many pins.

author: MikeK
author_rank: Super Contributor
timestamp: October 24, 2022, 12:34:51 pm
content: Quote from: Nusa on October 24, 2022, 07:08:26 amWhile that is a typical configuration it isn't the only one. Some alpha 7-segs are weird.bostonman, unless somebody posts a datasheet you're going to have to suss it out for yourself. Just be sure to use a current limit. If it helps, attached is a 2-digit alpha display I had that wasn't initially obvious. Don't be surprised if yours is similarly wacky. They were meant to be multiplexed, but not in the typical way of all segments of each digit in turn. I wound up not using mine and using a more sane display.

author: mariush
author_rank: Super Contributor
timestamp: October 24, 2022, 01:29:40 pm
content: Because there's so few pins, the digits "share" pins, so you display something by multiplexing, by turning on one digit, then turning it off after a short period and turning on the next digit.First you should figure out if it's common anode or common cathode display.Common anode means all the positives of the segments of a digit are connected together, and you'll have 8-10 grounds, one for each segment, plus one for the : between the numbersYou would have 4 anodes, one for each digit (and on one anode, you will also have the colon connected), so you give power on one anode, then connect individual segment cathodes to ground to turn segment.Common cathode means all the negatives of the segments are connected together, and you'll have 8-10 pins through which you can give voltage to turn on that specific segment.You would have 4 cathodes so if you want to display one digit, you send voltage through the 8-10 anode pins and connect one of the cathodes to ground.You can figure this out with a multimeter in diode mode or using a CR2032 battery ( it's 3v so higher than forward voltage of the leds in the segment but has high enough internal resistance that you would not burn out the leds). It's just a matter of connecting one wire to a pin, then testing all the other pins with the other wire from the battery. If nothing happens, flip the wires. When a segment lights up, you'll know the pin connected to positive wire of battery is the anode of a letter, and the other pin is the cathode.You can use 5v from a phone charger or computer usb or you can use 2 AA batteries in series or a lithium battery you have around, but then you need to limit the current by adding a 100 ohm .. 1kohm resistor in series with your positive voltage, otherwise you'll burn the segments.You can also go to a store and look at other similar displays, and see how their pinout isHere's a common anode one :https://www.digikey.com/en/products/detail/vishay-semiconductor-opto-division/TDCR1050M/4074708Here's the common cathode version :https://www.digikey.com/en/products/detail/vishay-semiconductor-opto-division/TDCG1060M/4074707Here's another common anode :https://www.digikey.com/en/products/detail/liteon/LTC-4627JR/408223Here's another common cathode :https://www.digikey.com/en/products/detail/liteon/LTC-4727JS/408220All the above have 16 pins, but yours will have an extra pin for some segments, or maybe it's just not connected to anything.Here's 14 segment (8 with x in the middle) displays so you can see some of the standard ways of wiring the extra segmentscommon anode :https://www.digikey.com/en/products/detail/liteon/LTP-3786E/121576common cathode :https://www.digikey.com/en/products/detail/sunled/XAMR14C2/4902136

author: rsjsouza
author_rank: Super Contributor
timestamp: October 24, 2022, 03:20:39 pm
content: The multiplexing might be very complex as mentioned by MikeK and mariush, but there is also the chance the extra segments are non-operational. I have a few 4-digit 14-segment displays that simply do not have LEDs mounted in the extra segments. I have absolutely no idea why these displays are like that, but it might well range from cost cutting to manufacturing defect (these were bought NOS a long time ago).

author: bostonman
author_rank: Super Contributor
timestamp: October 25, 2022, 12:22:55 am
content: I'll take a look to find out if this is worth diving into.I have about ten of these and thought the part number on the side would be enough to locate a datasheet. My first assumption was the ground is common, but then I realized I didn't have enough pins for a one-to-one (i.e. pin to each single segment).