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Topic: MAX7219 Alternative for 4 Digit 7-Segment display. (Read 4319 times) previous topic - next topic

adammhaile

I'm trying to figure out the best way to drive a 4-Digit, 7-Segment display and have found the MAX7219 chip to be very popular, but it is somewhat expensive and I'm wondering if there is something that would be smaller and cheaper, but able to run 4 digits of a 7-Segment display, instead of the full 8.  Is there anything out there that would do that?

Another possibility, however, would be something that could drive the 4 digits plus 3 RGB LEDs with PWM.  I know the MAX7219 has enough channels to drive all those LEDs, but it would be without PWM, which I absolutely need to have for the RGBs.  I'm already planning on using a TLC5940 for those, but having a single chip solution would be great.

Any ideas?

Grumpy_Mike

Quote
the MAX7219 chip to be very popular, but it is somewhat expensive

Popular and expensive usually means that there is no alternative. I haven't seen a cheaper one, more expensive yes nut not cheaper.

You can drive them like a multiplexed display but then the arduino would have to keep the display alive with software.

You would be better off using shift registers and drive the segments continuously instead of multiplexing them.

adammhaile

Ok, that's what I was afraid of. I'd seen other ways of doing it, but didn't want to have to continuously drive the displays. MAX7219 it is.

cjands40

You might take a look at the STLED316S - fairly cheap but surface mount only.  It's a "front panel controller" so it can handle switches as well as drive LEDs (common anode).

hexskrew

#4
Feb 18, 2011, 04:46 pm Last Edit: Feb 18, 2011, 04:50 pm by hexskrew Reason: 1
That was the dillema I was posed with, when figuring out how to drive my 8x8(x2 color) led matrix I bought from sparkfun, however for my alternative, I am just using the Atmega32L with the arduino bootloader. That way I have all the lights covered with one chip that ends up being cheaper than one MAX7219 chip. Go buy a pack of transistors, and your golden :)

Here's a proof of concept sketch I drew up in Fritzing.




I also have video and images of the POC as well since this is going to be a bigger project than just the matrix itself, and there are multiple concepts that are going into this system I am making.

CrossRoads

What is wrong with driving continuously? You just write to the shift register once and the data stays there.
You can also set up the shift registers to be independently loadable (common data, common shift clock, separate load clock, 6 pins total vs 3 with SPI) and just update 1 digit at a time like you would do with the 7219/7221.
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.

Cintax


the MAX7219 chip to be very popular, but it is somewhat expensive


Maxim allows you to order samples...

hexskrew



the MAX7219 chip to be very popular, but it is somewhat expensive


Maxim allows you to order samples...


I thought you had to be a distributor..

CrossRoads

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.

hexskrew


Nope, just a developer or a student.


Giggity! What kind of limits? Do I have to pay for shipping? Yeah I know I just need to go onto the site.. lol :P

CrossRoads

I've only asked for a couple at a time in case I smoked the first part. Free shipping. May take days for delivery if coming from the Phillipines or someplace like that.
Am waiting on some SPI driven USARTs right now to see about adding 2nd HW serial port at 230K transmit speeds.
Ordered a crystal from dipmicro to go with it. They are very inexpensive too, 5-25 cents for many parts, $2.xx for standard shipping.
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.

hexskrew

Yeah, that's why I wish there was some kind of local supply electronics supply house around here, because shipping is usually more than 1/2 the order on what I usually want to buy :\

Wish I could do reflow and smd soldering.. I have a board out of a lexmark printer that has a mighty fine stepper motor controller,  some kinda motorolla micro (useless though, proprietary and no schematic), serial addressable 512k chips, and a few other notable pieces. All I have is a cheap soldering iron I got for christmas two years ago. I have burnt the tip to hell and back (recently shaved and works pretty good still) but definitely not a fine tip.

CrossRoads

The dipmicro shipping is the least expensive of any that I have used, not complaining there,
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.

Cintax

#13
Feb 20, 2011, 01:36 am Last Edit: Feb 20, 2011, 01:45 am by Cintax Reason: 1
Maxim ships MAX72xx from California, I got some in the mail yesterday and I only requested them last week. There were sent via FedEx at no charge to me.

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