Tuesday, January 29, 2013

Another post on the meaning of 3D printing

I’ve been looking at the objects that I’ve uploaded to Thingiverse over the last year or more and there are some interesting points that occur to me (interesting to me anyway).  I think these will affect the economy of the future. I know, everyone and their dog has commented on this already, but I’m not slow, I’m just methodical in my thinking :)
One category of things that I’ve created are things that are completely unavailable commercially. Perhaps nobody’s thought of them before, perhaps I have a need nobody else has, more likely it’s not economically viable to produce them for one reason or another. Maybe they can’t be standardized so it’s not viable to produce them for mass market.
Another category is things that are commercially available, but either not exactly what I want (wrong color, size, doesn’t match my stuff, etc) or (I think this is interesting) it’s just easier/faster to print one than to go to the store or order one online.  In some cases the item is available but is difficult to find, is expensive, or shipping is expensive (sometimes more than the object costs).
The third category is things that are utilitarian and I can get easily at the store, but I don’t for some reason.  Perhaps they come in 10 packs and I need 2, and I don’t want the trouble of storing the extras for years then not remembering where I put them.  I’m rather like a squirrel burying nuts in that regard – unable to throw things away, but probably can’t find them when I need them either.
I will also happily admit that I will design something that’s available readily and inexpensively locally, simply for the fun of making it myself, and also because I get a charge out of thinking that people are out there making and using something I designed.  I will spend a couple of hours making something I could buy for $2, because I’ll be able to make them in a minute or two later and also because potentially hundreds of other people can now make them from my files.
So, possible economic impacts:

  • Shipping is reduced – bad for shipping companies, good for the environment
  • Excess production and waste is reduced – only make as many as you need, don’t store and search for them later.
  • Items are better suited to their use – you can customize all you like.
  • Problems are solved that might otherwise go unsolved, or are solved better.
  • Satisfaction goes up immensely.

Tuesday, January 15, 2013

Layer heights and Z axis drive rod


After a fun debate over on the G+ 3D Printing group, I have been proven wrong (which I do not mind at all – being correct is far more important than being right, if you know what I mean).  The discussion was regarding using SAE rods to drive the Z axis but choosing layer height based on nice round numbers of millimeters, like 0.25mm or something.
Turns out, that results in rounding errors, because for instance with a standard 18 TPI rod and a 3200 step revolution, 0.25mm (as an example) means 1128.888888888888 steps per layer.  This is going to result in rounding errors, so each layer will not necessarily be exactly the same height. It sounds miniscule but when I tried it last night, it really does seem to make a small difference.  The difference is magnified the smaller the layer height.
Moving to 0.254mm layer height seems to smooth it out quite a lot.
In reality it may be that moving to metric threaded rod is the best solution, then you have nice round numbers in the firmware for steps per millimeter.

Friday, January 4, 2013

Bicycle helmet cam experiences


I typed this up for BikeForums, figured I’d toss it up here as well.  This is regarding helmet cams for use on bicycles, in particular for commuting, video to be used as evidence in case of traffic incidents.
808 #16 keychain camera – OK video quality, honestly not much worse than many cameras that cost much more. However, battery life is almost nonexistant so you have to build something yourself, and that’s not reliable in my experience. Also no waterproofing, so it’s not a real solution.
Contour ROAM – Video quality about average. One switch turn on is nice. Problems: No replaceable battery, so you have to take it somewhere to charge every day or two. You have to connect it to a computer to switch modes. It has no circular recording so you have to connect to a computer every few days to clear the memory card (this is a ridiculous lack of features – it’s hard to find any other cam, even a $30 keychain cam, that doesn’t have this feature).
Chinese “ExtremeCam” – BIG. Apart from that, quite good. You can do everything on the cam, it has an LCD screen, it’s waterproof without an extra case, the video quality is good, it has removeable batteries and uses a common Fuji digital camera battery that are cheap and easy to find, it has every feature I’ve ever heard of on any similar cam. If only it weren’t so ridiculously large.
Sony ActionCam – pretty nice really, but the image quality really isn’t good. Video quality was only so-so, better than the keychain cams but probably worse than all the other cams I’ve tried. The still image quality looks like the photos came out of a camera that was found in the bottom of a cracker jack box. They’re embarassingly bad, very very VERY noisy.
GoPro Hero3 Silver – What I’m currently using. I have no complaints except that it’s not a Black edition. I will be buying one of those in the next few months, at which point the Silver will become my rear facing cam.  UPDATE May 29 2013 - I have since found a few problems with the GoPro.  It has a circular recording feature, but it's broken.  It's supposed to erase the oldest file when it runs out of space, but if you power it up in 1-button mode and it's full, it just says "out of space" and stops.  GoPro initially claimed that it must be because I'm using cheap memory cards, but it has since done it repeatedly with a genuine Sandisk Ultra UHS class 1.  Also, the GoPro is the worst device of any kind that I've ever encountered as far as card compatibility goes.  I have about 12 MicroSDHC cards, and only 2 of them work properly in the GoPro.  Moreover, once formatted in the GoPro, which uses a fairly non-standard format, only one reader that I own is able to read them, and I have to format them multiple times in my PC before I can then use them in anything else again.  I will NOT be buying another GoPro, and in fact I'm replacing it with another cheap Chinese camera (review to follow).

Tuesday, January 1, 2013

Basic equipment for casual electronics noodling

This is going to be a sort of glossary page for equipment that I mention elsewhere. It's not necessarily a shopping list or a buyer's guide, just a reference for what I'm talking about elsewhere.


Solderless breadboard

If you're going to do any experimenting at all in electronics, you need one of these.  They're really cheap and they will save you tons of irritation.  Here's what a breadboard looks like (image stolen from LadyAda.net)
When you plug a wire into the breadboard, a little metal spring inside makes electrical contact. Each row of five are all connected together (so on the left, a,b,c,d,e are all connected in the first column, a,b,c,d,e in the second column are separate from the first but all connected together).  To form circuits, you plug parts in then plug either other parts or wires in to other holes in the same column and they're connected together.

Using a breadboard you can quickly put circuits together and change them around in seconds.


Breadboard jumper wires
You can just cut bits of solid core wire, telephone wire (24 gauge solid core) works fine, but for very little money you can just buy a bunch of jumper wires with perfect little ends on them for working with breadboards.  Here are some jumper wires (image from adafruit)

Arduino
Arduino is a fantastic environment to get started with microcontrollers. There is a huge amount of help available online, the amount of stuff you can buy to interface with it to make your projects a reality quickly is almost hard to believe.  For one-off or very small runs of hobby projects, the Arduino is probably the way to go.  There are a lot of different Arduinos.  If you will be buying peripherals for the Arduino (called "shields") then you will want a shield-compatible board such as the Arduino Uno. These can be found on ebay for < $15
Arduino Uno


If you intend to build your stuff on a breadboard and possibly eventually incorporate it into a small board, then the Arduino Nano is a good choice.  You can plant it right onto a breadboard and wire directly to it.  Arduino Nanos are < $10 on eBay.  Be sure to specify "USB" - there are some versions without it.  Later if you want to really cut costs, you can buy the Arduino Pro Mini which usually does not have a USB interface - you use an external USB adapter to program them then unplug it when you deploy your design.
Arduino Nano USB

The Arduino family is pretty huge.  There's also the Arduino Mega which extends to much more I/O, more memory and a more powerful CPU.

There are other more powerful development environments such as the Raspberry Pi, BeagleBone Black and others which are basically small computers complete with networking, keyboard/mouse and monitor connections. If you need that kind of power, they're definitely worth looking at. My projects tend to be smaller so I stick to the smaller solutions.


Chip programmer
If you're going to play with Arduino, you don't need this - normal Arduinos have a USB interface built in.

However, if you are working on a project that will have a bigger number of items produced and it is cost sensitive, you may wish to use a smaller chip - AVR processors can cost as little as 50 cents in quantity.  If you're going to use microcontroller chips more directly, you'll need a programming device. All of my work is done with AVR chips, and these can be readily programmed with an "in-system programming" (ISP) device. I use the USBASP programmer, it's a little USB stick with a ribbon cable out the back. The cable goes to a 10 pin header, but I prefer the 6 pin, so be sure to get one with an adapter to go from 10 to 6 pin. You can find these programmers with adapters for < $7 on ebay.