Freesteel Blog » Internet of things thing wiring

Internet of things thing wiring

Tuesday, November 4th, 2014 at 11:14 am Written by:

I’ve begun various arduino experiments here in DoESLiverpool, which necessitated moving closer to Adrian’s desk on account of knowing no electronics, there being bugger all adequate instructions on how to wire anything up.


Oh yes, he says, obviously VCC is standard code for “power in” for that red square in the centre-left of the picture that contains a microSD card and requires 3.3V of power — even though this is nowhere stated and all the other circuits in this kit use 5V.


It’s not much of a standard when this is immediately contradicted by the thin thing on the bottom left of the picture (called a Jeenode) which labels its corresponding power pin “PWR“, and the low-power bluetooth blue board on the middle of the white panel which calls its power pin “VIN” for “voltage in”, and the red “real-time clock” thing above it which labels its power pin “5V“, which is so much better because: (a) it is immediately understandable by the man in the street, (b) it conveys the crucial information about the level of voltage required, and (c) it uses one fewer character when the labels are already too small to read without a magnifying glass which I do not have but should get.

So WhyTF do they use any of those other codes?

Ah, you might say, wouldn’t your logic require sometimes writing “3.3V“, which is four characters?

Well, no, actually, because the thing in the middle with the USB plug has two power pins on it, one called “5V” and the other called “3V3“, so they were forced to be sensible.

Of course, I’ll be proved wrong when I find a peripheral that contains both “VCC” and “VIN” pins.

Don’t get me started on all the other pin names, especially on the different arduino boards on which they’ve failed to mark out these all-important SPI pins that are either pins 11, 12 and 13, or pins 4, 1 and 3, or pins 51, 50 and 52, or you have to look it up on this handy diagram if you have a Jeenode.

I think electronics got off to a bad start from the very beginning when they decided that current flows in the opposite direction to the electrons. From then on it’s been seven human generations of miscodings and mistakes that have been adopted as conventions resulting in something not unlike spelling in the english language — ie you can’t see the problem once you have gotten used to it.

1 Comment

  • 1. Another Adrian replies at 4th November 2014, 1:34 pm :

    VCC has a specific meaning in electronics: it’s the collector supply voltage for a bipolar circuit (VEE would be the emitter supply voltage). Unfortunately, it often gets used as a general purpose label for the positive supply pin of many things. This is doubly annoying if you appreciate the original meaning, as VCC can be negative (for a pnp transistor), and many of the things you’ll be using won’t even have collectors because they will be CMOS, and therefore should have their supplies labelled VDD and VSS. Some are labelled correctly – especially so when a mixture of bipolar and CMOS devices are present in one thing and it’s important to know which bit you’re connecting to.

    It has been well said that the best thing about standards is that there are so many to chose from. Enjoy.

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