Interfacing to the MAX7313

E

Euanw

New Member
Hi all,

I need to PWM control many LEDs at once and have obtained some MAX7313 samples to give them a go.

Does anyone have any experience interfacing to these from an 18X? i.e. Does the PICAXE I2C protocol work well etc?

Many thanks

Euan
 
M

marcos.placona

Senior Member
Take a look at the manual for picaxe and i2c interface.

A picaxe 18x can handle that with no problem. I think it's more a matter of reading and understanding the datasheet. I haven't got experience myself with this chip, but what springs to mind now is the MAX7219 (loads of examples here) or even the cheap 74HC595 (cascaded) that can give you 16 digital outputs (more if you cascade more than two) http://www.picaxeforum.co.uk/showthread.php?t=9116

How many leads do you need to drive?
 
B

BCJKiwi

Senior Member
A single pwmout can control a MOSFET which supplies the power to all the LEDs. The LEDs can then be switched by any number of devices including PICAXE Ports directly (depending on loads/circuitry). Use MCP23017 16 port i/o expanders for most projects myself.

The MAX7313 has a couple of gotchas as far as I can see;
1. chip supply is 2 to 3.6V even though i2c and ports are rated for 5V.
2. ports are 50mA capable but max out at 20mA per port if all are on.
3. surface mount only (if that is a problem for you).
 
Last edited:
E

Euanw

New Member
marcos.placona said:
Take a look at the manual for picaxe and i2c interface.

A picaxe 18x can handle that with no problem. I think it's more a matter of reading and understanding the datasheet. I haven't got experience myself with this chip, but what springs to mind now is the MAX7219 (loads of examples here) or even the cheap 74HC595 (cascaded) that can give you 16 digital outputs (more if you cascade more than two) http://www.picaxeforum.co.uk/showthread.php?t=9116

How many leads do you need to drive?
Click to expand...
Thanks for the reply.

I'll need to drive approx. 128 LEDs (using RGB LEDs), each with PWM to control brightness. Any tips on a more appropriate way of doing it would be much appreciated.

Cheers

Euan
 
E

Euanw

New Member
Euanw said:
Now that looks like the job!

Fantastic, I've ordered a load of samples so I'll give these a go.

Many thanks for your help Hippy!

Euan
Click to expand...
Okay, one more question.

I see a lot of people saying that you must use MOSFETs to drive the LEDs from the TLC5940, but in the datasheet it says they can be driven directly.

Surely, if you're not exceeding the 80-120mA current sink capabilities of the outputs you don't need a MOSFET? Or am I showing my ignorance?
 
You must log in or register to reply here.
Top