My temperature sensor works (kinda)

After successfully hooking up a stepper motor to my Contraptor frame, and being able to control the motion in one axis, I returned to trying to get my temperature sensor board and thermistor working. I finally discovered that either my RJ45 breakout cable or the RJ45 jack on the board is bad. My initial problem was that I hadn't stripped the ends of the thermistor before connecting to the terminals on the board (hey, I'm a programmer not an EE). Even after that, all the readings from Arduino pin 0 were essentially random. I thought maybe that port was bad (or the header), so I tried pin 1: same thing. Eventually I tried connecting my jumpers directly to the .10" pads on the underside of the sensor board. Then I was consistently reading zeros. This thermistor came with the board, but is not physically the same size as the ones that I ordered at the same time. I am going to try using one of these larger thermistors to see if I get readings that are scaled better. If I still don't, I will have to look at populating the R1 location on the board (after first figuring out what this circuit is trying to do).

Personal Fabrication Update #2

I am still manufacturing Contraptor hardware, in order to bootstrap myself a RepRap.

I found a Canadian supplier of bearings (for the shaft mounts and linear bearings), and do I ever feel stupid because I knew of them all along.  Lee Valley sells sealed bearings for use as guides on router bits, and they stock the two sizes needed for Contraptor components (and 608s that would be useful for RepRap, however I already bought some skateboard bearings).  They also now carry more Starrett tools than before; I picked up a Starrett 819 automatic center punch (catalog #30N28.25,  I had been using a Veritas automatic punch with pegboard to manufacture perforated angle but it wasn’t up to the job of punching aluminum.

Here are some useful tips for building the hardware that the Contraptor folks either neglected to mention, or figured you already knew.  I’m telling you now because I did it the hard way first.  If you are using paper templates to lay out your cut lines and hole locations, glue it down with a glue stick.  I tried spray adhesive, but that was too slippery (and then a real pain to remove when it dried).  Place the paper on your angle with light pressure, adjust to proper position and then press down.  Leave it for a minute or two, and then it’s not moving at all.  There is also no need to remove the template before drilling.  In fact it’s easier to line things up (and you don’t get confused and drill the wrong size hole somewhere).  You also don’t need to remove the template before sawing (again, I thought I’d make a huge mess and lose where the next line would be).  Cutting the aluminum with a hacksaw is not such a pain (especially with a 32TPI blade and a good saw), I tried using my compound miter saw with a carbide blade, but the kerf is too thick so it throws off all the dimensioning (especially for templates).

Personal Fabrication Update

I've been spending the last few evenings manufacturing Contraptor elements. Tonight I've half-finished some sliders (I need to find a source for UHMW PE channel to complete them). I'm getting faster and more accurate. Tony G. says that he cuts aluminum with his carbide-tipped blades in his saw, so I gave it a try tonight. I used the cheapie Mastercraft mitre saw instead of the Makita with the expensive blade. It's noisy but it works. The 8.25" Mastercraft blade is only 24 TPI instead of ~ 60 on the Makita, so the edge is a little rough. But it's square, and takes about 1/10 the time of cutting with the hacksaw. Especially the 6063 square tube.

I'm using the template method on the sliders, but gluing the paper on with spray adhesive. I mounted the template last night, and then did all my drilling and countersinking tonight after it had a chance to dry (I went a little crazy with the glue, but that made it easy to adjust the positioning). I don't have a 6-32 tap, so I didn't tap the holes. I may try using steel 6-32 screws as a poor man's tap. Tomorrow night.

One Word

Mr. McGuire: I just want to say one word to you - just one word.

Ben: Yes sir.

Mr. McGuire: Are you listening?

Ben: Yes I am.

Mr. McGuire: 'Plastics.'

Ben: Exactly how do you mean?

Mr. McGuire: There's a great future in plastics. Think about it. Will you think about it?

Ben: Yes I will.

Mr. McGuire: Shh! Enough said. That's a deal.

OK, how about two words: Personal Fabrication.

3-D printing is getting ready to hit Main Street. Commercial machines, costing thousands of dollars, have been used as prototyping tools in industry. Now a new breed of DIY machines (RepRap, RapMan, Fab@Home, MakerBot) are available to the hobbyist. Granted, these machine are not as fully functional as a $10,000 machine, but they are a disruptive technology (cf. sustaining).

People have said to me “what would I use one for?” I don’t know — yet — but they will become ubiquitous. I think personal fabrication is at the same stage now as the personal computer was in 1975 (when the Altair 8800 was introduced), or the web in 1993 (when NCSA Mosaic was released).

I am building a RepRap. However, RepRaps are self-replicating — many of the parts are printed on RepRaps — there is a bootstrapping problem. Correction, I am building a RepStrap using Contraptor components, with which I will build a RepRap. Right now I am manufacturing Contraptor perforated angle.

Tiny Apps are a good idea

I like the idea of Tiny Apps: get something out there after a night's work. But there's a bit of infrastructure that needs to be set up:

• if it's a "thick" app, where do I store it?
• if it's a web app, where do I host it?

I suppose there are also browser add-ins, they'd have the same issue as thick apps.

Some web apps can be run on Google App Engine, I suppose. Or I could fire up an EC2 image. How do I pay for the EC2 usage? Maybe that's step 2 after I get something that people like.

lim Ruby->Python

I find it a bit ironic that Ruby now checks your indentation for you. The fact that Python only uses indentation for block structure means that the compiler and the (human) reader are both using the same rules. It also means that you don't end up with hundred-line long methods (I've had to debug perl programs with functions that went on for pages). Ruby syntax is still a little too perlish for my liking (but maybe it's because the ruby book I have is not very good).

I had a dream last night

I woke up from a dream about 2:30 this morning, thinking "that was a very cool idea I should implement. I should write it down so I don't forget it in the morning". I think it was software, but it might have been hardware. Did I write it down? No. Do I remember it now? No. Sigh. But, as Zoe says, writing down ideas you have in dreams is like writing poetry when drunk: they don't look as good in the morning.

I attribute it to attending DemoCampVictoria02 yesterday.

The annoying part is that I thought I didn't have a pen on my night table, so I would have had to get up and go find one. But I did. Here's hoping I can redream it tonight.