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Typical LEDs to be used with MaxO


#1

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.


#2

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.


#3

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…


#4

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

http://m.ebay.com/itm/110909403870?nav=SEARCH&sbk=1


#5

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 :slight_smile: ) 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!


#6

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


#7

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 :slight_smile:


#8

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!