10 Pin Dual 7 Segment Display...cant find documentation

[JCoder]

Hey Guys,

So I was scrapping parts from an ancient present I found up in the attic called the "Singing Machine". Point is I managed to retrieve a dual 7 segment display. The only documentation I can find online is for 14 pin versions of these things. Strangely this only has 10 pins and I can assure you none broke off. Anyone have any idea what these pins match to?

[fleem]

Hey Guys,

So I was scrapping parts from an ancient present I found up in the attic called the "Singing Machine". Point is I managed to retrieve a dual 7 segment display. The only documentation I can find online is for 14 pin versions of these things. Strangely this only has 10 pins and I can assure you none broke off. Anyone have any idea what these pins match to?

It should be pretty simple to figure out. Put a 10K resistor on a 5-15V power supply, then in a darkened room touch the leads to different pairs of pins. Once you know what's what, crank the current up for reasonable brightness.

[JCoder]

I kinda expected to get that answer. I have been playing around with the pins for about 2 hours now but most of them seem to be multiplexed.

[berkeman]

Can you post a picture? Are there any markings on it?

[JCoder]

Picture is attached

[berkeman]

Interesting. Googling the part number doesn't turn up anything helpful (but you knew that already). To drive two sets of seven segments takes at least 9 pins if you share the segments and just have two different common cathodes or common anodes per digit.

You said you did some beeping -- were you able to identify a CC or CA or two?

[JCoder]

The strange thing is this was used for a track number display for a CD so both 7 seg's must have been controlled differently. Pin 7 when + turns on the right screen and Pin 8 + turns on the left screen. When both are + both screens go on. Whenever I change the other pins they change both screens so I am confused as to how to change each screen individually. Pin 2 when - is the d.p. Each Pin is an annode because it is only affected when in the - side. I believe I am describing this correctly. Sorry I am not very familiar with describing it other ways.

[Bob S]

Interesting. Googling the part number doesn't turn up anything helpful (but you knew that already). To drive two sets of seven segments takes at least 9 pins if you share the segments and just have two different common cathodes or common anodes per digit.
If I were designing this, I would use the 10 pins for Vcc, ground, and two BCD 1248 signals. The 4 line to 7 line decoders would be inside the chip.

[berkeman]

The strange thing is this was used for a track number display for a CD so both 7 seg's must have been controlled differently. Pin 7 when + turns on the right screen and Pin 8 + turns on the left screen. When both are + both screens go on. Whenever I change the other pins they change both screens so I am confused as to how to change each screen individually. Pin 2 when - is the d.p. Each Pin is an annode because it is only affected when in the - side. I believe I am describing this correctly. Sorry I am not very familiar with describing it other ways.

So it sounds like each digit is configured with a common cathode (- side), with the two CC pins providing multiplex access to the digits. Each of the pairs of 7 segments share an anode pin. So your drive circuit will need to drive the two digits in an alternating fashion, with each digit being on for 1/2 of the time. Drive them above the flicker fusion frequency of the human eye -- something like 50Hz should be fast enough, but you can experiment.

[JCoder]

Berkeman, that actually makes alot of sense. Thanks for the help everyone.

[kris22]

maybe this can help you.
http://www.theelectronicshobbyist.com/blog/2010/06/arduino-2-digit-7-segment-display-with-buttons/

[Jiggy-Ninja]

If you want a picture to help you visualize what Berkman is talking about, here is the data sheet for a 4 digit display:

http://www.sparkfun.com/datasheets/Components/LED/7-Segment/YSD-439AK2B-35.pdf