Computing stuff tied to the physical world

Archive for March 2015

From LPC810 to LPC812

In Book on Mar 25, 2015 at 00:01

No, I haven’t abandoned the Micro Power Snitch!

But some projects are trickier than others, and this one didn’t want to play along when I tried it again on my new PCB design. I fixed one glaring wiring mistake so far, but there’s more going on. Since Mr. Murphy seems to be enjoying himself again, I’m going to let him enjoy his little “victory” for a while and come back to the MPS at a (slightly) later date.

Instead, let’s move up the ladder a little and experiment with another ARM µC:

DSC 4977

On the right: four times as much memory (both flash and RAM) and twice as many pins.

As you can see, packaging is everything – and bigger is not always more…

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Micro Power Snitch, last part

In Book on Mar 18, 2015 at 00:01

In this concluding part (for now) about the Micro Power Snitch, which feeds off the magnetic field around an AC mains power cable when in use, I’ll look into how the whole circuit behaves when it comes to actually sending out wireless radio packets.

The daily articles in this week’s final MPS episode are:

Update – With apologies (again!), I’m going to postpone the following posts:

It’s a huge challenge to manage the incoming energy so that everything keeps going!

(For comments, visit the forum area)

Micro Power Snitch, part 4

In Book on Mar 11, 2015 at 00:01

At the end of the day, the Micro Power Snitch (MPS) is really about powering up and down robustly under all circumstances. There will be times when there is no energy coming from the Current Transformer, and there will be times when energy levels hover around the go/no-go point of the circuit. That’s the hard part: being (very) decisive at all times!

This week’s episode looks at an improved circuit with a dozen individual components or so. As you will see, it has excellent snap-action behaviour, and does the right thing on the “up” ramp as well as on the “down” ramp, regardless of how slowly those voltage levels change.

DSC 4958  Version 2

Here is the daily sequence for this week:

With a complete MPS circuit design worked out, we’re finally getting somewhere.

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Micro Power Snitch, part 3

In Book on Mar 4, 2015 at 00:01

There’s trouble ahead for the MPS: it’s not reliable enough yet, and can enter a “zombie mode” whereby the µC won’t have enough voltage to start up, while drawing so much current (relatively speaking) that the energy source isn’t able to raise the voltage further.

Leading to some beautiful pictures, but nevertheless totally undesired behaviour:


The daily articles in this week’s episode are:

So far, it looks like this second MPS design solves the problems of the first. Progress!

(For comments, visit the forum area)