[MinnowBoard] 1.6V output on gpio pin

[Anders, David]

Trevor,

Hehe, you didn't say you had the datasheet for the LED! Hehe

Dave


-----Original Message-----
From: elinux-MinnowBoard [mailto:elinux-minnowboard-bounces at lists.elinux.org] On Behalf Of Trevor Woerner
Sent: Saturday, February 6, 2016 4:29 PM
To: MinnowBoard Development and Community Discussion <elinux-minnowboard at lists.elinux.org>
Subject: Re: [MinnowBoard] 1.6V output on gpio pin

Hi Ken,

On 02/05/16 19:28, Ken Tait wrote:
> The proper way to do this is something like this:
>
>
>
> connect LED_1 to your GPIO pin. You can use almost any small fet. I 
> don't recommend a transistor, if so you will have to put in a pull 
> down resistor to completely turn it off.
>
> Resistor R12 controls the current and therefore the brightness 
> depending upon the led you are using. Different colors require 
> different currents since their voltage drop is not the same. Try not 
> to go below about 120 ohms..10-20ma is sufficient to light most leds.
>
> Ken...hardware designer and software guy :-)

Yours is the solution that worked for me.

I Found the sheet that came with the LEDs I bought. All it says is that if my voltage is 5V that I should use a 330 Ohm resistor. Even though my voltage is only 3.3V I used a 330 Ohm resistor for R12 anyway.

I don't have any BSS123's or 2N2222's on hand (I should probably get
some) but I do have BC337's which seem to do the trick as well.

For my R3 I'm using a value of 270 Ohm.

David: it looks like my gpio is still fine since I am able to measure 3.3V (when it is on) between it and ground with no load.
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