Straw Poll - LED Driver Chip

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DDJ2011

Member
Hi,

I'm drawing up plans for an LED cube. I'm going to start at 3*3*3 single colour and progress from there. My aim is to reach 8*8*8 with RGB LEDs.

I'm going to multiplex the LEDs and need to expand the Picaxe output ports through the use of one or more shift drivers (depending ultimately on the size of the cube I go for).

I have read many articles about this and would like some input from you on which LED drivers to select. There are so many out there.

Do I go for SPI or I2C?
More outputs = fewer components but presumably higher cost for the chips? For example I can buy 10 74HC595s for £1. Only 8 lines each so more required, but they cascade and are dirt cheap.

So, thoughts and ideas please on which chips to buy (I have a separate thread for the technicalities of building cubes).

Many thanks,

DDJ
 
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DDJ2011

Member
Did Westy replying put people off?

Some of you must have used LED driver chips and have an opinion on them, surely?

Share them here and help me and others out - there are so many to choose from out there that personal recommendation is a good thing.
 
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gbrusseau

Senior Member
I believe in giving people a second chance, but please don't bite the hand that feeds you!
Take a look at the TLC5940 LED controller. No matter how you look at it though, an 8 X 8 X 8 RGB cube is over 1500 LEDs. Will probably require more than a few PICAXE's syncronized with each other.
 
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BillyGreen1973

Senior Member
The MAX7219 is a 8x 7 seg display (including decimal points) driver, it can directly control 64 common cathode LED's.They are controlled via a serial connection and can be daisy chained to give larger numbers. The LED output is latched too, so between serial commands it keeps the display lit. There is a single 'blank' and a single 'test' command for easy trouble shooting.
Check the datasheet for more detailed info.

http://datasheets.maxim-ic.com/en/ds/MAX7219-MAX7221.pdf

They pop up on fleabay now and again fairly cheap. I got 20 of these IC's for £2!
 
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DDJ2011

Member
gbrusseau said:
I believe in giving people a second chance, but please don't bite the hand that feeds you!
Click to expand...
Apologies - I am so used to seeing lots of replies that I thought something had gone awry. No disrespect intended as I have received lots of help here before.

Thanks to gbrusseau and BillGreen1972 - I will investigate your recommendations.

Incidentally, 8*8*8 RGB is 512 LEDs but more than 1,500 solder joints.
 
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westaust55

Moderator
DDJ2011 said:
Apologies - I am so used to seeing lots of replies that I thought something had gone awry. No disrespect intended as I have received lots of help here before.

Thanks to gbrusseau and BillGreen1972 - I will investigate your recommendations.

Incidentally, 8*8*8 RGB is 512 LEDs but more than 1,500 solder joints.
Click to expand...
512 phyicial LED entities, but if they are RGB LED's then *3 = 1536 individual LED elements.

I have not used the MAX7219 but in summary they are SPI interface and each chip provides 16 outputs .
Since they are primarily for 7-segment display driving, the chip has onboard brightness control and RAM to hold data which in a more static situations would reduce the PICAXE data throughput requirements. However with any more dynamic display, I think the data throughput will be as high as feeding data into other forms of basic IO expander chip to continually change the colour and illuminated pattern. IMHO, I don’t think it is well suited to multiplexing 1500+ LEDs.
The Texas TLC5940 is again a specific LED driver chip with SPI type interface and 16 outputs, each dedicated to driving an LED. With a high “drive” current sink rating (60mA constant current or even 120 mA) which is a better proposition than the MCP23017 basic IO expander chips I had suggested, but by virtue of the open collector outputs, would still need extra circuitry on some outputs if you wish to multiplex LEDs to reduce to overall chip count.
 
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