Return of the dreaded disease

Posted on August 4, 2011 by Skye Sweeney

Last night as I making for algorithm changes to my lightning detector, I experienced an unexpected reboot. Never mind, I was probing with a scope lead at the time. That likely caused the problem. But after a few minutes it became clear that I had a problem. The same problem that scuttled my sailboat race start timer. Continue reading →

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Data from my lightning detector

Posted on August 2, 2011 by Skye Sweeney

Here is a sample CSV file from a lightning storm that passed through my area on August 2, 2011 at around 5:30PM.

sparks_38

Here is a sample piece of that CSV file:

1312198123.414 8 187.975 8
1312198123.416 0 0.002 8
1312198123.430 16 0.014 23.8
1312198123.433 0 0.003 23.8
1312198123.437 6 0.004 29.8
1312198123.439 13 0.002 42.7
1312198123.441 0 0.002 42.7
1312198123.447 23 0.006 65.7
1312198123.450 0 0.003 65.6
1312198123.454 11 0.004 76.6
1312198123.456 40 0.002 116.6
1312198123.458 0 0.002 116.6

First column is the time in Python time (seconds since Jan 1, 1970)

Second column is the reading from the detector.

Third column is the difference in time since the last result.

The last column is the result of the following algorithm. Sum the new raw value with this running sum, and subtract a gain (10) times the deltaTime from the sum. Do not allow the sum to go less than zero.

You can see large blocks of time (deltaT in the hundreds or thousands) where nothing happens. Then you get the occasional spark that is detected, but is washed away from the decay part of the algorithm. Only when a large number of sparks come in at one time, does the sum reach a warning threshold (2000) and then a danger threshold (3000). From this data I plan on refining the algorithm. Stay tuned!

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HomePowerMonitor with a CS5460A?

Posted on August 2, 2011 by Skye Sweeney

A poster on the Sparkfun forums (donnib) clued me into the Cirrus Logic CS5460A Power/Energy IC. This part appears to be designed specifically to be the backbone of a power meter. It takes as inputs the instantaneous voltage and current and generates real power measurements as well as instantaneous power. Continue reading →

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HomePowerMonitor on an Arduino? First tests.

Posted on August 2, 2011 by Skye Sweeney

Using an Arduino for my Home Power Monitor (HPM) has many advantages. It is cheap, simple, small, and has a good user base behind it. But could it meet my requirements (more on these in a future post)? To find out, I started to prototype the software last night and time it with my scope. I was pleasantly surprised. Continue reading →

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Start of a HomePowerMonitor Design

Posted on July 31, 2011 by Skye Sweeney

So what does one do when you want to put in a whole home power monitor? Hit Google of course. After many hours of searching, I found numerous consumer power monitor systems and countless industrial systems. The industrial systems where mostly completely outside my league. Most did not even including pricing (“If you have to ask, you can’t afford it”). Of the consumer systems most were lacking.

The most common deficiency was that lack of individual branch circuit monitoring. They would either look at the whole house as one measurement, or at best give you a measurement on each phase. No consumer system had the hooks to instrument each branch and that was what I really want.

But in looking at all these systems, I started to get the idea about how they worked. For the single measurement types, they would often clamp a device on the meter to watch the wheel spin or the light blink. Or they might clamp a sensor on the main power line to measure the magnetic field generated on one phase. The two measurement systems used clip on current transformers (CT).

These doodads are little plastic devices you snap over a single wire. Inside is a metal doughnut and wire windings that generate current in proportion to the amount of current flowing through the wire you instrumented. The current can be transformed into a voltage with a “burden resistor” and monitored using your choice of electronics.

The output of a CT is not an average current, but rather an instantaneous one. Since homes run on AC power, this means the CT generates an AC current and (via the burden resistor) and AC voltage. You therefore need some smarts in your electronics to convert an AC voltage of varying amplitude into a measure of current.

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Sources of data on Home Energy Monitoring

Posted on July 31, 2011 by Skye Sweeney

This posting will be updated with external sources of information of power measurement. Continue reading →

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Power monitor

Posted on July 28, 2011 by Skye Sweeney

Over the last few years my wife and I have noticed out electric bill getting larger and larger. This is not surprising with the cost of everything going up, but what does bother me is that our usage of power has increased.

Why are we using more power? What is consuming the extra? Continue reading →

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Trouble with Reset

Posted on July 25, 2011 by Skye Sweeney

I have been working on an MSP430 based sailboat start timer. For those readers not into sailboat racing, races as started by a series of “guns”. At predetermined times before the start of a race, the race committee creates an audio signal (shotgun with blanks, airhorn, cannon, …) . The sailors use these to attempt to get their boat to an invisible line between two buoys at the split second the time reaches zero. It is a complex task that requires lots of practice.

So I attempted to make my very own timer. A small motorcycle battery with a little micro to drive a car horn at the proper times. This I could place on the dock of my lake cabin and I could practice as long as the neighbors would allow a car horn going off. Continue reading →

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Indoor Lightning

Posted on July 25, 2011 by Skye Sweeney

Strange as it may be, my lightning detector goes off every few minutes… but without the thunder and blinding flash of light. Continue reading →

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A Max Hold Circuit

Posted on July 25, 2011 by Skye Sweeney

Since the conversion rate on the MSP430 would not reliably see my piezo sparks, I decided to try my hand at a max hold circuit. I considered using a simple RC circuit to try to capture and stretch out the pulses, but this seemed to be outside the scope of what I could reasonably do. Continue reading →

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