8x8 LED matrix with the MAX7219

If I were to make an 8x8 led matrix using the max 7219, would I need any other components? Or would I just need the leds, the max7219 and my arduino? I saw this product http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2127970_-1 I would just buy the kit but I don't really want to spend $60 and I already have a bunch of leds and an aruinod so I'd really only have to buy the MAX7219 and any other components. Anyway this kit comes with 2 resistors, 2 potentiometers, and 2 capacitors in addition to the leds and max7219. But, looking at the schematic, I can't figure out what they do. So, could someone tell me if I would need any other components and, if so, what they would be? Thanks

Check out the ones on adafruit that include the I2C back pack.

https://www.adafruit.com/products/870

trendz3: If I were to make an 8x8 led matrix using the max 7219, would I need any other components?

Hi trendz3,

You will need a resistor to set the overall brightness of the matrix. Ideally the value of this resistor would be based on the exact specification of the LEDs in the matrix you are using (the forward voltage and maximum current). But I always use 10K and have never had any problems with that (except once when I used really, really cheap LEDs from eBay!).

You should also use 2 caps: a 0.1uF and a 10uF. It may well work without them, but its good practice to always use them to avoid strange issues that can arise if you don't, which could cause you to waste a lot of time trying to figure out what's going wrong. They help smooth the power supply to the chip. As LEDs get rapidly switched on and off by the chip, this can cause ripples and dips in the power connections that can affect the chip and any other chips and components in your circuit, even the Arduino itself.

$60!?! Hard to see how they can justify that for those components.

Paul

CarlW: Check out the ones on adafruit that include the I2C back pack.

https://www.adafruit.com/products/870

Thanks this is definitely better than the $60 jameco one. But it does use a different driver than the max7219. The end result of my project will be an 8x8 matrix incorporated into a table top, so basically a table and the tabletop is the matrix. So the matrix will need to be bigger. Do you think it would work if i recreated the circuit on a larger scale? Because adafruit has some nice libraries of code to use with this

PaulRB: Hi trendz3,

You will need a resistor to set the overall brightness of the matrix. Ideally the value of this resistor would be based on the exact specification of the LEDs in the matrix you are using (the forward voltage and maximum current). But I always use 10K and have never had any problems with that (except once when I used really, really cheap LEDs from eBay!).

You should also use 2 caps: a 0.1uF and a 10uF. It may well work without them, but its good practice to always use them to avoid strange issues that can arise if you don't, which could cause you to waste a lot of time trying to figure out what's going wrong. They help smooth the power supply to the chip. As LEDs get rapidly switched on and off by the chip, this can cause ripples and dips in the power connections that can affect the chip and any other chips and components in your circuit, even the Arduino itself.

$60!?! Hard to see how they can justify that for those components.

Paul

I agree to the $60, it's outrageous. But as for these components, where would they go in the circuit?

The resistor would go between +V and ISET. The two caps go between +V and GND as close to the chip as possible.

Yes, no problem making a larger matrix by spreading out your leds. I made a 4x4x4 cube using max7219.

If you download a copy of the datasheet for the MAX219 you will find the circuit that everyone uses as part of that datasheet. How to size the resistor is also part of the information supplied. Google is your friend.

Don't need google for that - go right to the source, www.maxim-ic.com