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Topic: Driving 14 or 16 segment LEDs (Read 1 time) previous topic - next topic

Oracle

Is there a good way to drive 4 14-segment LED's?  I'm looking for something comparable to a MAX7219.  I'm aware of the option of using a couple of shift registers and a transistor for each digit, but would prefer a driver that takes care of all the multiplexing and current drive for me.  I've seen SMD chips that will handle 8-digits but I need through hole parts. 

Thanks

CrossRoads

Check maxim-ic.com.
They have 14-segment drivers, might need 1 per chip. Or maybe will have 1 that does 2 chips.
But really, using 2 shift registers and a ULN2003 or TPIC6B595  is not that hard.
Write a blink-without-delay piece of code: at the top of void loop, you check for 500uS, or 1-2 mS, passing, pull the next digit of data from an array and write it out and turn on the next cathode driver for common cathode displays , or anode driver such as UDN2981 if you have common anode displays.
The rest of the time your program does whatever it does.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Oracle

Thanks for your reply.  I did look at the data sheets for the MAX6654/6655 type chips, they seem quite a bit more complicated to use than the 7219 because they try to be so much more versatile; more LED arrangements, a built in port extender, etc.  I also don't think I can get them in through-hole which might be a problem for me.

Those chips also support 128 LED segments which is one reason for the complexity.  From your post, can you point me at any drivers that do 1 or 2 digits?  I only need 4 digits so that won't be so bad for me.

Using 2 shift registers, a transistor array, and resistors will up my component count a lot.  Programatically, I'd use a timer interrupt handler to do the multiplexing so I could have a set-and-forget interface which I find a lot cleaner than blink-without-delay, but that whole scheme seems so inelegant.  I'm just surprised it's such an easy thing to do with 7 segments but so hard with 14.

I thought the 14-segment display would be a pretty solution, but it's at the point where I'll probably just go with a character LCD.

Grumpy_Mike

#3
Aug 03, 2012, 12:33 am Last Edit: Aug 03, 2012, 08:01 am by Grumpy_Mike Reason: 1
Quote
also don't think I can get them in through-hole

Yes you can, look at the data sheet for MAX6954. I have some myself.

CrossRoads

Did you look at MAX6954? Write to a register, it does all the multiplexing for you.
6954 is SPI interface, comes in a DIP. Be like using a MAX7219/7221.
http://datasheets.maxim-ic.com/en/ds/MAX6954.pdf
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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