Computing the volume of a cat

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Cat volume computation

How do you compute the volume of a cat?

Dunking it in water doesn’t work– you only get the volume of the rat-like creature that lives inside the cat; much like the feeble alien within a Dalek. (And, if your answer had anything to do with contour integrals, get real.)

Here is a low-tech method that works: Using successive approximation, determine the smallest box that the cat will fully enclose itself in, and measure the size of that box. Cats tend to leave a few appendages hanging out of the corners– you may need to assist with folding the cat into the box for the final stages of approximation.

This cat is approximately 648 cubic inches in volume.

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Class Reminder: Choosing a Microcontroller (Sat 7/7 @ TechShop)

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ATtiny2313MakeController

Tomorrow I’ll be again giving my seminar called “Choosing a Microcontroller” at TechShop. This class is a broad introduction to the capabilities and variety of single-chip computers, as well how to actually pick one for a given application. It’s easy to get overwhelmed looking at the variety of range of micros, from four-bit micros that have a 4-bit wide data path — and actually cost four bits— to AVRs and PICs, basic stamps and Arduinos, to 32-bit gorillas with names like ARM, Blackfin, and Coldfire. So, we’ll try and cut through the fog and help you figure out where to get started.

If you’ve heard people getting excited about or doing cool things with microcontrollers and want to learn more, this might be a great introduction to the field.

Sign up for the class here.

If you are interested in the topic but can’t make it, you might want to take a look at our
list of resources for choosing microcontrollers.

This is the last time that this particular class will be offered in the near future. Another intro AVR class will be forthcoming, probably in August. As always, if you have other ideas for classes that are within our expertise, please let us know.

This entry was posted in Education, EMSL Projects, Microcontrollers and tagged , . Bookmark the Permalink.

Urban Art at Morrow’s Nut House

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Toadstools

Nut HouseWhile wandering around San Francisco, we ran across Morrow’s Nut House. There were some very silly decorated walnuts in the window, but that’s not what caught my eye. I couldn’t take my eyes off of the toadstools just outside. These capped-off pipes had been painted red with white spots. Urban art at its finest! Of course, the name of the shop is pretty good, too. Unfortunately for us, it was closed. Next time. In the meantime, you’ve got to check out the reviews people have written about this place!

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Cooking hot dogs via electrocution

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cooking   LED 1

How to cook hot dogs… with electricity!

[Disclaimerzilla: While we could give you lots of warnings about all the different dangers involved and how to possibly skirt them, the simple truth is that this just isn’t safe. If you are foolish enough to attempt this, you will have to deal with pointy things, raw electricity out of the wall, hot steam, and the possibility of fire. If that isn’t enough, and you succeed, you are still faced with the possibility of having to eat a hot dog. In summary: do not, under any circumstances, cook hot dogs this way.]
Continue reading Cooking hot dogs via electrocution →

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Cellphone charging stand

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Cell phone charging stand

Lamp...or charging stand?Here is a simple solution for a common problem: where to put your cellphone while it is being charged. This multiple gooseneck floor lamp (aptly named “Hydra,” available at Home Depot) can do double duty as a cellphone charging stand, freeing up valuable shelf or desk space for more important uses. It nestles your gadget inconspicuously out of the way but still readily accessible while charging.

One caveat: this lamp has a dimmer switch, and we haven’t yet found reasonably priced dimmable compact fluorescent bulbs, so bulb options are limited to incandescent or extremely expensive.

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Casting class at TechShop

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finishing the pour

We attended an aluminum casting class at the TechShop last week and had a great time! It was totally hands-on and absolutely unintimidating. The instructor did an excellent job of getting all the students (all five of us! – perfectly sized class) involved and getting our hands dirty. When I wasn’t busy with tamping sand or other fun tasks, I took some pictures, which are in this flickr set.

The TechShop offers a wide range of classes, and based on our experience as students, they are great. They are having an open house this weekend, so if you’re in the area (Menlo Park, CA), you can check it out for yourself. Open house details can be found on the event schedule.

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Reminder: Upcoming classes at TechShop

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led micro-readerboard   Blinkylights1

Build your own LED Micro-Readerboard this Satuday (6/30, 1:00 PM) at TechShop. It’s a single class where you choose phrases for and solder together your own LED Micro-Readerboard. As a new option: you can choose to make yours an AlphaPOV display! This class is a fun first introduction to what you can do with a microcontroller– where you make a neat toy that you get to take home. (Kids can take this class too, assuming that you’ve already taught them to solder.) Sign up here.

A week later, “Choosing a Microcontroller” (7/7 @ 1:00 PM) is a detailed seminar on the capabilities of microcontrollers and walks you through the process of finding one for your application. Sign up here.

This entry was posted in Education, EMSL Projects, Engineering, Microcontrollers and tagged , . Bookmark the Permalink.

AlphaPOV: An alphanumeric persistence of vision display

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AlphaPOV4

You have probably seen persistence of vision (POV) toys at some point– little LED dot-matrix displays that, when waved around, display a picture or a message that seems to hang in mid air. We’ve been playing with 16-segment LED displays lately, and it some point it occurred to us that we’d never seen an alphanumeric POV display. So, we went ahead and tried it out, and hey– it works! AlphaPOV is the result. It’s a neat effect since the clearly defined segments– designed for text– introduce a certain degree of legibility into the display.

The starting point for building this project is our LED Micro-Readerboard. Normally, the micro-readerboard shows one character at a time, so that you can read it sequentially while holding it still. Here, we use a (very slightly) modified version of the firmware that blinks the characters on and off at high speed. Read on for details, AVR source code and a few more pictures.
Continue reading AlphaPOV: An alphanumeric persistence of vision display →

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Quick hack: The $1 C-to-D adapter

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Quick C to D adapter

Here’s a common problem: You want to power your gizmo that runs on D cells, but all that you have handy are C cells.

In many (but not all) circumstances, you can solve this problem by using the C cell and making up the battery length difference with a few quarters– typically three or four. There is a 12 mm length difference between a C cell and a D cell, and quarters are about 2 mm thick, so if your gizmo has a really weak spring it could take up to six quarters to do the job.

Yes, commercial battery size adapters are available.

They typically cost between 1.5 and three dollars and can only be used for the one purpose– adapting battery sizes. (Well, that, and as a set of matryoshki.) Using quarters can also potentially end up costing as much as $1.50, but it can go straight back into your wallet when you’re finished! Much more importantly, when you really need it, you can probably find a few quarters no further away than your pocket.

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