Wednesday, June 25, 2008


XKCD is one of my all time favorite comics. It is at the very least amusing. Sometimes it clues me in to an internet meme which I missed out on (I probably have 10 years on Randal, so I am a little outside his demographic). There is frequently something of value to be learned. And once in a while it hits me as the funniest thing ever.
Today hits a little close to home.

Check out the archives. There are some great ones in there.

Tuesday, June 24, 2008

And the spinner was detected

I had some time to run my sensor on the real meter last night and was able to read the spinning disk with some reliability. It was not in full sun, so that test remains. I didn't drag my oscilloscope outside with me, so I don't know how close I got to saturation, but I am now hopeful. There was some noise in the output when pointing the sensor on the edge of the disk (it has a surprising number of imperfections). I had better luck moving the sensor above the disk and pointing it down.
The next step is to optimize the design by removing any unnecessary components, and cleaning up the output to produce a clean digital output. I also have to figure out how to mount the thing nicely.

I will be connecting the sensor to a microcontroller and sending the resulting data out via a wireless link to my main computer. The plan is to put the data on the web.

I created a first pass schematic including the microcontroller, I was able to route it all on one metal layer, which simplifies things from a manufacturing standpoint. This is important because I manufacture the boards myself, and have no plated thru-holes! I'll post the final design when I am done.

Monday, June 23, 2008

The vomit maker goes on vacation

This is one of my infrared shots from a trip we took pre-children.

She was still pretty much a puppy here, but she did a nice job sitting still for this shot. I believe this was in Jackson, WY. I don't know the story behind all the antlers, but I believe they were collected from a nearby wildlife reserve.

West Nile

Guess what happened to me in 2004.

you can clearly see Colorado's northern front range in this map.

We have signal

After messing around for a while I am getting good results with my phototransistor design by using AC coupling and some opamp buffering and a gain stages. Next up is to see if my phototransistor gets saturated in full sunlight. To get around it, I might have to add some IR filtering. Shading the meter would be a good option, but I think the electric company might have issues with that...

Oh, if you are just tuning in, check out my power post to get some context. This is my device for optically reading the spinning disk on my electric power meter so that I can compute peak power demand and make an informed decision on changing my electricity rates.

Friday, June 20, 2008

A box full of awsome

For my wedding anniversary I received a great geek gift. Theodore Gray is someone I would greatly enjoy hanging out with. He appears to have a rocking workshop, and a fantastic collection of almost all the elements in the periodic table. He also does some kick-ass photography of his items. Furthermore, he went ahead and put it into an attractive poster and sells it.

This poster can be seen in the background in many of the Mythbusters scenes. I got the 22"x44" size, which is a good healthy poster size. There is an even bigger one available, but that one would have a hard time fitting in my laboratory. (Note that these are an odd size, and custom framing is required if you decide to go that way)

Utilities - a history

Playing around with the very cool Google Docs today. I went ahead and populated a spreadsheet with my utility history. The charting features are somewhat lacking, so I couldn't do a very fancy graph, but here it is anyway:

It would be nice to annotate the graph with significant events, like the winter months during which the waste water rate gets computed, and the summer months when the AC is on. Also, it would be nice to have a dual Y axis range. In this graph, I had to multiply KWH/day by a factor of 10 to keep the ranges similar. Yucky.

I took the first steps to design an automatic reader for my electric meter and bought a IR phototransistor and an IR emitter. My fears were that a simple phototransistor would not be sensitive enough for this purpose. So far, my fears were justified. I am going to do some signal conditioning with some active filters and see where that takes us. If the phototransistor is a bust, then I will purchase a nice PIN photodiode with a built in amplifier. If THAT fails, I may have to resort to designing some sort of optics to reduce the noise level to something reasonable.