Computing stuff tied to the physical world

LED polarity

In AVR, Hardware on Aug 17, 2009 at 00:01

Ok, first puzzle solved. I had the two 0603 LEDs reversed.

The silly part is that I had actually built a test rig to make sure this wouldn’t happen:


As trivial as it gets: a battery with a series resistor. By holding the SMD LED against two copper contacts it’s easy to check which side is which. Here’s a green LED lighting up:


Then I got confused and placed all the LEDs exactly the wrong way around – doh!

There are three copper pads. The middle one is PLUS, the other two are GROUND.

Ok, now the RX+TX LEDs blink a few times when plugged in. Onwards!