driving LEDs

Hello, I’m new to the world of micro controllers. I have a pretty good background in electronics, (took a certificate course a few years back) but very little in programming. before i jump in, i want to drive(actually control is probably a better word) fairly large arrays of LEDs for moving arrow boards hand held traffic signs, emergency vehicle lighting and simple LED animation. is the Arduino a good way to accomplish this? from what i’ve seen so far it looks good!

Any thoughts?

Thanks Gary

Slower animation which you’ll be wanting is dead simple with the Arduino.

I’d use the MAX7921. It drives a 8x8 grid so if you want bigger you just hook more up together (they only need one set of pins).
Its also rather light on the battery because only one LED is on at any time yet it still looks good.

Thank You Cheater!
Good advice, I’m gonna get one and work my way thru some tutorials, i was lookin for an excuse to get one to experiment with anyway.

Thanks again for your input!

Gary

Hi,

I’d use the MAX7921…
Its also rather light on the battery because only one LED is on at any time yet it still looks good.

If you meant MAX7221, not quite right, The MAX7221 always switches a group of 8 Led’s on or off.
Still saves a lot of power though.

Eberhard

I think Cheater meant the 7219. There’s also a newer 6950 & 6951 from Maxim.

Yeah yeah I meant the 7219/21. :stuck_out_tongue:
The 21 uses SPI while the 19 doesnt. Only difference.

The MAX7221 always switches a group of 8 Led’s on or off.

No, it does a 8x8 array of LEDs. Also works well with 8 7 segment displays.

Hi,

No, it does a 8x8 array of LEDs. Also works well with 8 7 segment displays.

Yes, thats why its a 8x8 Matrix. But concering the maximum supply current it is important to understand,
that at any given point in time a group of 8 Led’s are switched on or off, depending on the data sent to the device.
Since there is a chance that all Led’s of the group are on at the same time, the maximum supply current to be expected is 8 times the current that was set on the hardware-side (Resistor ISet, see datasheet).

Eberhard

But concering the maximum supply current it is important to understand, that at any given point in time a group of 8 Led’s are switched on or off

Uuuh no. Only one LED is on at any one time with those chips.
Go read the datasheet.

Hi, Cheater

But concering the maximum supply current it is important to understand, that at any given point in time a group of 8 Led’s are switched on or off

Uuuh no. Only one LED is on at any one time with those chips.
Go read the datasheet.

I did when I wrote the LedControl-Lib, all of it!
You probably want to read the section Computing Power Dissipation on page 11 in the datasheet again.
The equation clearly shows that the number of lit segments (Leds) is relevant to the power-consumption (Factor N).
It also mentions the worst case scenario : 8 segments (Leds) lit.

If you need another proof, see the Electrical Charateristics Table on page 2.
In the third row Operating Supply Current there is a value given for the matrix when all 64 Leds(segments) are lit.
If the Led-(segment-) current is set to 40 mA (Resistor ISet) the resulting Current is given at 330 mA.
Thats 40 mA per Led (segment) plus some extra 10 for internal chip-logic.

Eberhard