16-Segment LEDs Sticks on eBay

tomcrawford

There are some 16-segment 4-character monochrome displays that have recently showed up on eBay. They come in various colors. You can have a look by searching "16-segment LED".

Here is a demo of a font I made. The left two characters are the ascii character; the right two characters are the ascii code.
http://youtu.be/oyiSs0KbOmQ

Of course, the segment decoding is different from anything else in the world. I did most of the characters except a few that I just couldn't stand.

There is a problem with the v4 data sheet; the pinouts for data and clock are swapped.

The segment diagram in the v4 dat sheet is right side up when the connector is on the bottom. That is sort of good because it means the character you send first is on the left.

Dr_Acula

Nice work - that is brilliant!

Are the displays the ones that are coming up on ebay at about $32?

CuriousOne

One of popular hobby supplier haves them in 2x16 segment configuration for $0.79 ea.

Dr_Acula

@CuriousOne, yes I have quite a few of those - ie just the display. Sitting in the parts drawers on my shelf making me feel guilty for buying them and not using them Tom's design uses a module that also includes the driver chip, and the drivers can get quite complex as you need 16 pins per character, constant current (ie lots of resistors, or a smart chip), and then if you start adding multiple chips you need to multiplex, but if you multiplex you need driver transistors and also can't go beyond a certain number of characters before the display gets too dim. So it gets really complicated to think about, say, a 16x2 alphanumeric display (which I would *really* like to build!).

Just as an aside, video's of these led displays make them look kind of blurry - they look so much sharper in real life.

CuriousOne

Maxim has dedicated chip for these displays - MAX6955, it has built-in ASCII font too, so interface is easy.

tomcrawford

I should have said earlier that these are *not* my design and I have no connection with embedded-adventures, an outfit in Great Britain, who is selling them. I just like to fiddle with LEDs, perhaps to atone for killing the first sample I ever saw, sometime in the early 70s. Also, I like to write PASM.

These are based on the Texas Instruments TLC5926, a 16-bit shift register with programmable constant-current outputs. They use one per character.

The MX6955 looks like a very nice chip, driving up to eight 16-segment characters and including a key-pad scanner. I'm a little surprised not to find anything based on it on eBay.

MJB

tomcrawford wrote: »

The MX6955 looks like a very nice chip, driving up to eight 16-segment characters and including a key-pad scanner. I'm a little surprised not to find anything based on it on eBay.

see this
http://www.ebay.de/itm/8-bit-Segment-Module-Tube-TM1638-Digital-Dual-Red-LED-Display-Driver-For-Arduino-/181471888031?pt=Wissenschaftliche_Ger%C3%A4te&hash=item2a4091429f

and there are other offers as well

LoopyByteloose

Here is a YouTube demo of an Extremely Rare 22-Segment LED display.

why is it that I only count 16 segments? And, what about the 14 segment LED display?

http://www.youtube.com/watch?v=D2cyZoCat_U

http://en.wikipedia.org/wiki/Fourteen-segment_display

tomcrawford

That is majorly cool. There really are 22 segments; at about 2 minutes they show a diagram. They even have a dot for the lower case i and j, as well as descenders.

I think I shall return, now, to 8 x 8 matrixes. They have all the advantages of bit maps. You can do any font and you can scroll on a pixel basis. They are cheap and readily available (at least monochome and red/green/yellow).

CuriousOne

You haven't seen specific 16/22/34 segment led displays, made for Asian languages. I had photo somewhere, will try to find it. Regarding the question, why there's no cheap Chinese boards using MAX6955, I believe that this is because of reason that MAX6955 is not cloned yet by Chinese, as they did with MAX7219 already (remember I've posted a video, where MAX7219 bought off ebay, had cathodes reversed?)

__red__

The MAX7219s are functionally replecated by austrian semi. AS also have some other sexier LED driver chips in their range too!.

MikeDYur

Tom, I wonder if you had done any work with the TM1638, I bought this off of eBay just because, well you know why. Do you know of a good excuse use for it? There is nothing on OBEX and this is the only thread that came up on a search for the chip.

http://m.ebay.com/itm/New-8-Bit-Digital-LED-Tube-TM1638-Keypad-Display-Module-For-Arduino-UNO-R3-Due-/182230531683?hash=item2a6dc93e63:g:aaUAAOSwHgVW76R6&_trkparms=pageci%3A38565855-5be5-11e6-9ec1-74dbd1e05f28%7Cparentrq%3A605623af1560a2505512b4b2fff71da8%7Ciid%3A16

TM1638 is an LED Controller driven on a 1/16 to 14/16 duty factor. 10 segment output lines, 8 grid output lines, 8 segment/key scan output lines, one display memory, control circuit,
key scan circuit are all incorporated into a single chip to build a highly reliable peripheral device for a single chip microcomputer. Serial data is fed to TM1638 via a three-line serial interface. Housed in a SOP28 package, TM1638 pin assignments and application circuit are optimized for easy PCB Layout and cost saving advantages.

tomcrawford

Hi, the short answer is "no". I googled 'tm1638', though and got a bunch of hits, including youtube stuff. Data sheet seemed to indicate it has a vanilla SPI interface.

MikeDYur

Thanks Tom for the reply, I pulled a couple of different datasheet versions off of net, have been looking for some arduino code, to see if it would help. The only thing that I can light so far is the power LED. The chip can scan an 8x3 keypad, and there are some versions of the board with 16 buttons. A great little I/O board for less than $2.00, if you can find a use.

MikeDYur

Did anyone here put one of these together, I done two of them back in the mid 70s. I can't find a good example of the board, this one looks homebrew. I miss having the old RS nearby, the one near me is useless to buy a resistor, transistor or even a microcontroller anymore.

kwinn

I assembled a lot of multi-digit displays using those chips way back when, but never used the RS board. In a few early Propeller chip projects I used ULN2803's.

Do you need a single digit led display for something?

MikeDYur

kwinn wrote: »

Do you need a single digit led display for something?

No, I probably have the chips to breadboard that circuit, no reason to. Just wanted to show the younger crowd what it took do get one digit going. Maybe someone has an example of the board they wish to share.