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Topic: Good LED Driver IC for 121 Bi-color LEDs? (242 pins)( common-cathode) (Read 4561 times) previous topic - next topic

TECH GEEK

I'm looking to buy a few LED Driver IC's for an 11*11 LED Bi-color display. Here is what I need:


  • Adjustable Brightness for each output pin is preferred but not required.

  • 242 LED's must be controlled individualy (not all via 1 IC)

  • Each of the 242 LEDs uses up to 10mA w/ resistors in series (also, what is the minimum mA's "THIS LED" can use?)

  • the IC must use serial or i2c

  • must me in DIP form and be @ a reasonable price

As always... Thanks for posting!!!

floresta

Have you considered the Microchip MCP23017 (I2C) or MCP23S17 (SPI) IO extenders ?  Each chip has two independent 8-bit I/O ports.

Don

Grumpy_Mike

Common cathode LEDs are not very common and so not many chips are designed to drive them.
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what is the minimum mA's "THIS LED" can use?

There is no minimum, the smaller the current the dimmer it is but you will always get some photons out of it for some current through it.

TECH GEEK


Common cathode LEDs are not very common and so not many chips are designed to drive them.


Really? That is all i seem to find when I look at bi-color & RGB LEDs...
As always... Thanks for posting!!!

floresta



Common cathode LEDs are not very common and so not many chips are designed to drive them.


Really? That is all i seem to find when I look at bi-color & RGB LEDs...


What do you expect - he drives on the wrong side of the road, his light switches are upside down, his electrical outlets have too much voltage and low frequency, and he spells some words wrong.  Actually I think Mike is referring to 7-segment LED displays not bi-color LEDs.

Don

Grumpy_Mike

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and he spells some words wrong

Who invented the language?  :)

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Actually I think Mike is referring to 7-segment LED displays not bi-color LEDs.

No, why do you think there are very few common cathode LED drivers? The reason is that traditionally you always had a greater current sink capacity from logic gates than current source. So it made sense to drive them with current sinking. This is no good for driving common cathode LEDs.

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his light switches are upside down

I didn't know that.

No matter how hard the U.S try we will always be at least 5 hours ahead of you.  ;)

TECH GEEK

I don't know we are talking about common anode when the led the subject is about is common cathode...

Still want a good led driver IC
I think I will revise what I need from the driver:

  •   The more ports (aka. output pin) that can be individually controlled on 1 chip the better, so long as the price-per-port ratio is reasonable

  •   Each port needs to be able to control the brightness of the led,
    while still allowing the LED to be directly powered from the LED driver's port(typical 7.5mA // 15mA max @ 100% duty cycle?)

  •   Built in current control would be nice

  •   Serial control or I2C (if any other type please include a link to a tutorial)

  •   DIP chips only

  •   Needs to keep the selected ports on/off until the chip gets a new command

  •   Total cost to control 242 ports on however many ICs needed should cost less than $35.00 USD


As always... Thanks for posting!!!

sixeyes

I'm not sure it meets all your requirements but the MAX7219 / MAX7221 will allow you to drive 64 LEDs (32 Bi Colour C/C LEDS). You can chain them but depending on your update rate that may not be suitable.

TECH GEEK


I'm not sure it meets all your requirements but the MAX7219 / MAX7221 will allow you to drive 64 LEDs (32 Bi Colour C/C LEDS). You can chain them but depending on your update rate that may not be suitable.


what do u mean by the update rate?
It needs to be controlling a 11*11*11 Bi-color LED cube... with only one layer on at a time. (121 Bi-color LEDs max on at any time)
so it would need to cycle between 11 to 22, (22 layers if i have only one color per layer on at a time,)
layers at a rate that the human eye will see no flickering... 40Hz???? I don't know for sure...
As always... Thanks for posting!!!

sixeyes

The MAX7219/MAX7221 is controlled by sending a 16 bit command to the chip. If you want individual control of each LED you're going to have to send one command per LED. If you have 242 LEDs and 40Hz that means ~ 10,000 updates a second, so you've got lots of time. There is a library to drive the chip although I've not used it (yet).

Grumpy_Mike

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although I've not used it (yet).

That is quite clearbfrom this rubbish
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If you want individual control of each LED you're going to have to send one command per LED.

no you don't.
This chip is totally unsuitable for the op

sixeyes

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This chip is totally unsuitable for the op

Totally unsuitable seems harsh. It will drive common cathode LEDs. What makes it so totally unsuitable?

Grumpy_Mike

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What makes it so totally unsuitable?

OK maybe it is harsh but I think it is true, the OP said:-
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I'm looking to buy a few LED Driver IC's for an 11*11 LED Bi-color display.

That chip handles an 8 X 8 matrix for a single colour. So how are you going to extend it to handle an extra 3 columns and rows and an extra colour? It's internal memory is only 8 X 8.
So how do you propose using that chip for this situation?
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and be @ a reasonable price

This is an expensive chip, are you suggesting that he uses three of them?

sixeyes

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That chip handles an 8 X 8 matrix for a single colour. So how are you going to extend it to handle an extra 3 columns and rows and an extra colour? It's internal memory is only 8 X 8.
So how do you propose using that chip for this situation?

I was planning to use the chip myself for use with bi colour common cathode LEDs. That's why I posted when no one else had suggested anything. If you have 4 LEDs per bank and 8 banks per chip. I was imagining that he would need 4 chips.

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This is an expensive chip, are you suggesting that he uses three of them?

Depends where you source them. I bought 5 on ebay from Hong Kong for < £10. But I agree if you're buying from Farnell / RS it's way too expensive.

TECH GEEK

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I was imagining that he would need 4 chips.


yeah except every single cathode is connected to ground, so no columns or rows, just 121 or 242 pins to control...
As always... Thanks for posting!!!

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