Dyslexia

Perhaps I have a twinge of numerical dyslexia. In my work I order stuff online from Farnell who use six or seven digit order codes. I can think I have committed such a code to short-term memory then type it into my order and find I have the digits in the wrong order. Often I know I am writing it wrong, but cannot be sure what the right way is. This happens so frequently that generally I have resorted to writing down even the simplest of codes. It is the same with telephone numbers.

SOT23-5 semiconductor package

Microchip make amplifier chips and specialise in lower power rail-to-rail input and output types, and these I find useful in my work. Recently I chose the MCP6401 in SOT23-5 package from the many to choose from.  So I ended up ordering the MCP6041 by mistake, and after re-ordering got mixed up between the MCP6401 and MCP6041R.

Whilst similar there are enough differences between MCP6401 and MCP6041 to matter, and you can see that MCP6401R has a different pin-out. So I decided to purge my stocks and only keep the MCP6041R for which I have a symbol in my PCB-CAD software. In the design I am currently working on I used this symbol only to find I had mixed up the two pins VIN+ and VIN-.  Duhhh...

My next catastrophe was with LED's. I needed a high-brightness red indicator LED and chose one by Cree in a PLCC-4 package. You'll see from my picture that three of the legs all connect to the cathode of the LED, and one to the anode. And there is a diagonal line "cathode marking".

PLCC-4 LED package

In a subsequent project I wanted high-brightness LED's in different colours so manfully chose a bunch from the Farnell online store only to find, after designing my PCB and soldering them in, that they didn't work because they use the four pins differently. I had naively assumed all PLCC-4 LED's would use the same pin-out - indeed, why-ever not?

There's a moral somewhere...