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Building a hygrometer with a HS1101

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The next sensor I wanted to add to my home was a set of hygrometers. Specifically I wanted an exterior one, and a matching interior one. This would be useful as we have evaporative cooling, and if the humidity level outside is already high, then it doesn't make a lot of sense to put extra water into the air. Worse than that, it can also damage my books and make the house really clammy. So, adding some sensors was the first step in some form of alerting. I picked up two HS1101s from ebay quite cheaply (about $4 each IIRC). These devices are capacitors whose capacitance varies proportionally with relative humidity. You also need to provide a temperature at the sensor to correct the value, although the correction is pretty minor so I guess you could skip this if you really wanted to cut costs. Given I have plenty of code for Dallas 1820s now, I just dropped one of those onto the board too. I just used the circuit from the data sheet for my design, with a few simple tweaks (like the DS1820). Here's my surprisingly unprofessional circuit diagram: The DS1820 stuff that's not on the data sheet…

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The Man in the Rubber Mask

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I'd been looking for this book for ages, as it is quite rare, so it was exciting to find it at Gould's the other day. This is the memoir of the dude inside the rubber mask that Kryten wears in Red Dwarf. The book is an easy read, and entertaining, although I wouldn't call it funny. Most of the book focuses on how terribly horrible it is to be encased in rubber day after day while shooting a comedy in terrible locations. Oh, and Robert is slightly insecure which doesn't help. Overall I'm glad I found this book, and glad I read it again. [isbn: 0140235752]

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The Renegades of Pern

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This book starts off in quite a disjointed manner, with the introduction of a variety of seemingly unrelated characters. The only thing that they all have in common is that they're holdless. However, as the book progresses these characters are all weaved together into a relatively cohesive story line. I say relatively because there are gaps in the story telling, which can be a little jarring. Interestingly, this book also clarifies some of the events of the others in the series. Most satisfyingly it includes more detail of the buried settlement at Landing than The White Dragon did, which ties in nicely with the introduction provided in Dragonsdawn. This gives me hope that later books will take the science fiction track I've been wanting them to for a while. [isbn: 0345369335]

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Asimov’s Mirage

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If I was to name one flaw with the Robot City and Robots and Aliens series, it would have to be that they're not very good. They're lackluster, have difficult to believe plots, very simple structure, and are overall poorly thought through. Its a similar sensation to that I feel when I read the tie-in books written after Harrison's Bill the Galactic Hero series. I feel a little sorry for the writers in later books in these series, because I suspect their hands were tied by the poor decisions of previous authors (similarly to the mess that Bear's Foundation and Chaos had to dig that series out after Benford's tragically terrible Foundation's Fear). Robot City and Robots and Aliens were disappointments because I read Roger MacBride Allen's Caliban series before them, and Caliban is ok. Not awesome, but ok. I say all of this as an introduction to Mirage. I guess what I'm saying is that I've been wading through Asimov robot tie-ins from other authors for a while now, and some of them are not very good. That's why finding Mirage was such a delight. Its well written, has a similar style as Asimov's own writing, reuses characters and…

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The Beer Fridge saga continues

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Since the last update on the beer fridge, we've had to do some murdering of the original PCB to get it to fit in a case. In addition, we'd failed to take into account the startup power draw for the compressor (5 amps), and had to upgrade the relay we're using from a 3 amp solid state relay. Luckily Doug had the beefier relay just sitting around in his shed. That means we've lost our opto-isolation because the new relay is a simple mechanical one, but we have a relay coil doing the same thing now. A new PCB will make the world a lot neater, which will be nice. Oh, we've also been mentioned on Hack a Day, which has generated some interesting comments on their site. I've observed that sometimes the relay doesn't turn on, even though the arduino thinks it has done so. An example can be seen here: (Note that graph is a Google chart server image, generated by a simple visualization program I wrote in python. If you're that way inclined, the visualization software is in my public SVN repository). At first we thought this was a software problem with comparing ints to floats, but…

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Buy Jupiter Short Stories

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This is another Asimov short story collection. The following stories appear in the book, although I have already read a couple as part of either the Robot short stories or the Nightfall collection of short stories. To be honest these stories aren't Asimov's strongest. They entertaining, but they're not as amazing as some of his other stuff. I guess its hard to be a genius all the time. The following stories appear in this collection: Buy Jupiter1975 The Complete Robot1982 Robot Dreams1986 Darwinian Pool Room Day of the Hunters Shah Guido G. Button, Button The Monkey's Finger Everest The Pause Let's Not Each an Explorer Blank! Does a Bee Care? Silly Asses Buy Jupiter A Statue for Father Rain, Rain, Go Away Founding Father Exile to Hell Key Item The Proper Study 2430 A.D. The Greatest Asset Take a Match Thiotimoline to the Stars Light Verse [isbn: 0575041994] [awards: nominee nebula_short_story 1965 (Founding Father)]

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Thinking about arduino as a prototyping platform

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So, I've mentioned in earlier posts about arduino projects that I consider the arduino to be a prototyping platform, and a damn good one at that. Hack a day seems to think of it in similar terms. It was really Doug who got be thinking in this direction with the initial PCB design for the fridge controller project, which includes space for an Atmega CPU right on the PCB, thus eliminating the need for a relatively expensive arduino board to be permanently consumed. So I started to wonder how hard it would be to build a simple arduino replacement board. It wouldn't need the complicated USB hardware, as you could program the Atmega on a full arduino board before installation. It would just need a time source, perhaps a LED, and a voltage regulator. You can see in the picture above a version I quickly whipped up on a breadboard to prove this is possible. I didn't bother with a voltage regulator in this version, and the wires off on the right go off to a power source. This quickly turned into a PCB prototype board design, which has a voltage regulator, and exposes all of the arduino digital pins…

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Colony

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The Times is wrong about this book. Its not "cruel, cynical and very funny", its cruel and cynical for sure, but it lacks hope and is overall just depressing. I certainly didn't feel it was funny. Its strange, I loved the Red Dwarf series, and this book is very similar. I think the problem is that this book lacks all the hope and charm of the Red Dwarf books and TV show. Its a book entirely comprised of Rimmers, and that's hard to take. [isbn: 0140289755]

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Arduino with the kids: Cricket Noise Door Bell

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When I was a child, I had a doorbell at my bedroom door to ward off uninvited guests. My six year old, Matthew, has always been pretty enthused about building things, and so he wanted to give an electronics project a try. I thought this would be a good project to start out with for the kids, because its relatively simple, and there is a tangible result at the end (you press a button and something happens). Matt liked the idea. Because this project involved a fair bit of soldering, it turns out that Matt spent most of his time taking photos of the work, although we talked about what was happening at each step. I need to think harder about how to get him involved in the construction process -- I think that will be easier once the bread boarding stuff from ebay arrives. The design is relatively simple. I took the sample debounce circuit (a button, 10k resistor) and software and ran that first. Then we put a peizo buzzer across pin 13 and ground. That meant that with the sample software we had both a light and a noise when you pressed the button. Unfortunately, the pin…

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