# Typical LEDs to be used with MaxO

Hi

I’m up to a project using one or two MaxOs to drive some leds (the standard ones you can stick into a hole on a thin wooden board). I read the ports have a 330 ohm resistor built in.

What LEDs would one typically use? I’m currently looking on mouser.com, and can’t seem to find any LED that would fit the 3.3V / 330 ohm nicely.

I understand that the formula for calculating the forward current is: I = (V - Vf) / R
E.g. using Vf = 1.9V, V = 3.3V, R = 330 ohm yields I ~= 4.2 mA

The closest matching LEDs I can find are 2 mA (would break) and 10 mA (probably not enough to really light it?). It’s the same for all other Vf I tried.

I feel lost. Thanks in advance for any helpful answer.

The calculation is to get primal brightness. I wouldn’t worry about the numbers. Any typical led will work well. Also I would buy the leds from eBay, really cheap. Or look into hobby stores like sparkfun.

Welcome to the community.

Gus, thank you for your answer. I’m new to the hardware field. Could you give me an example of a “typical LED” that would work? I want to build something that has a couple of LEDs and i’d like to avoid re-order in case I got the wrong ones, mainly due to excessive shipping prices (to switzerland) compared to what the LEDs cost on their own…

Here is an example but the Internet has tons of other options

To expand on Gus’ answer, for example a 10mA rated LED would just be dimmed, it would still light, if your calculation is correct (specifically if your rated resistor value is correct, it probably isn’t ) You won’t have a problem, just buy some LEDs of the type you want from eBay, whether you want square through-hole (TH), round through-hole, or surface mount… I would buy a big bunch of TH and keep in your parts bin!

What is the ‘rated resistor value’? I only mentioned one resistor value, the 330 ohm. That comes directly from the MaxO spec…

I didn’t describe that well, did I…

I meant if you say it’s 330ohm, based on documentation, you can almost guarantee it’s not 330ohm. It’s probably a 10% tolerance, so you’ll always get slightly different brightnesses from multiple LEDs on the same family of resistors. Just don’t get hung up on it, buy some LEDs and you’ll get visible light

Meanwhile I received what I has ordered. In case anyone has the same question:

http://ch.mouser.com/Search/ProductDetail.aspx?R=TLHE4600virtualkey61370000virtualkey78-TLHE4600

These LEDs are pretty much OK, connected without any additional resistor.

Cheers!