LCD, led and current

hi,

I'm working on a project which (hopefully) will include an LCD and 25 leds. I's wondering if arduino can handle the total current without the need of external components§ (?)

Finally, I know the current for each led is 20mA but I do't know how much current an LCD needs in order to operate properly.

thanks

25 LED's each drawing 20 mA = 500 mA + the LCD, this is already over the total current you can draw from the Arduino board i think. Assuming that all the LED's are on at the same time.

So you my advice is to use an external powersupply

hi MikMo,

I'm trying to keep my project USB powered if posiible.. Any workaround?

Also, the 24 leds are used with 3x4051 multiplexers.
I don't know if my assumption is correct, but even if all the LEDs are on at the same time, in theory there should be only 3 LEDs on at exactly the same time, if you know what I mean?

Am I missing something?

thanks

You should be Ok if only three LEDs will be drawing current at any one time. I run a backlit LCD and an optical mouse powered off the 5v USB supply with no problems.

I agree with mem.

If only 3 LED's are on at any given time, there's no problem at all.

There have been a few different opinions about the total currenthandeling capability of the Arduino board, but if my memory serves me i think it landed around 300 mA without a heat sink on the voltage regulator.

Any individual pin can source 40mA

in order to avoid confusion...

All the LEDs seem to be "on" at the same time. Is just me that I think that with the 4051, in theory there should be only 1 led "on", even if it looks like all the LEDs are "on". Still don't know if this assumption is correct.

thanks for you replies guys..:slight_smile:

I think you are right.

The input of the 4051 can only be connected to one output at a time.

cool, thanks MikMo ;D