Saturday, October 9, 2010

Physics Projects

I love Advanced Lab. PHYS 427, is easily my favorite class this semester. I have to stop myself from spending too much time on it, like I am doing right now.

For the class we have three remaining projects, two small labs, and one major project. I have about five to do.
1. Finish the vacuum chamber. This is an ongoing process. It's about 96% done. Still have a few little things left to tweak. Hopefully I can find time to post about them as I move along.

2. Finish the thermal evaporation plate. This one is a really fun project. I am making a thermal evaporation system for the vacuum chamber. We'll be using it in lab to make a half silvered mirror and some Hall effect samples. I am making it essentially from scratch, most of the design is original, with a lot of inspiration from google image searches. I'll continue to post about that separately from the vacuum chamber as we go along.

3. Make a half silvered mirror. This involves finished the evap system, and will serve as a test for it. If we can successfully make a mirror I think I can say the build was a success.

4. Inverted pendulum. For our PID loop project I choose to make an inverted pendulum. Initially I plan to use LabView to implement the algorithm, but maybe later this semester I'll program an Arduino and make the unit self contained.

5. Hall effect. This one is a doozie. I am currently working to set up a hall effect measurement experiment. Right now that involves a lot of research into techniques and methods for doing it. Hopefully all that knowledge will coalesce into something tangible over the next few weeks. I hope to have something physically established for it by the end of October, giving me plenty of time to work on actually getting it to work before the end of the semester.

Some pictures from the lab.

Tuesday, August 17, 2010

ASS Part 2: Getting the screen under control.

It has been a while since I last posted about ASS. I have made a fair amount of progress, and at my current rate, with what still needs to be done, I see myself finishing this project and completing installation by the end of this week. It's a good thing too, I don't know when I'd have time to work on it during this semester.

I received my parts from sparkfun the other day. I like how the parts come in a little red box.

I hooked up the motor driver and had some fun playing around with controlling the motor. I did not hook up the screen because I had not integrated the encoder yet. I decided after some testing that my motor driver was a bit puny. I went back to sparkfun to order the next size up. I got it a couple of days ago, and hooked it up. After a few more tests I liked what I had.

Next was the encoder. After reading these tutorials:

I had the encoder pretty much locked down. After some slight modification and meshing of the code from the second tutorial I was able to produce what is currently busy to my left. I have the controller set up to move the shade up and down using the encoder as feedback. It has been running for the past 45 minutes or so, the driver chip seems to be warm but nothing too hot, and the screen stop positions haven't drifted noticeably.

Needless to say I am very proud of this auto-shade, rolling up and down. It's a bit silly, but I like watching the screen roll itself up and down.

These brief descriptions do nothing to detail how the encoder was mounted to the screen dowel. This portion of the project was especially fun for me. I had to couple the encoder to the dowel so that it could monitor the rotation and know how far the screen had lowered. I ended up using the encoder as a portion of the mounting system, just like the motor is used as a part of the mounting system. I didn't have any good shaft couplers around my house at the time, so I just grabbed the nearest thing, which was an old gear with a set screw. It fit the encoder perfectly and with enough modeling cement, it fit the end of the screen dowel too! This is by far the weakest link in my system so far, I will probably want to revisit it at some point.

I used some old wire wrapping wire to make a nice header pin for easy connections on the encoder bracket. It occurred to me that I might want to move this thing around, so making things modular was important.

Friday, July 16, 2010

Decay-o-scope (Peltier cooler cloud chamber)

Some of you may be familiar with my rant about how this guy stumbled upon the brilliant idea of using thermoelectric cooling and built it before I did, receiving internet credit points for the idea. I am not going to repeat my rant here, instead I give the person mad props for thinking of the idea, and then finding the time to actually make it. If it wasn't for ASS I would have probably also made one by now. But now with the end of ASS in sight, I am beginning to assimilate parts for my next project, the Decay-o-scope.

Cloud chambers are really neat, and since I am into nuclear stuff, I decided a while back to build one, eventually... Then I learned all about Peltier coolers while working at ERG, and had the great idea of using the thermoelectric devices in a solid state cloud chamber! Most of the time cloud chambers are built using dry ice, or some kind of refrigerant system. Using a solid state device would dramatically increase convenience, and portability. Not only that, but the coolness factor goes up by orders of magnitude.

I have a far off plan of eventually building some kind of furniture (coffee table?) around such a solid state cloud chamber (SSCC). To start with though, I want to build a proof of concept. Since Rich beat me to it, I figure I can build my own version, with some extra stuff (and extra size!).

First off, there are a couple of things about cloud chambers, apart from the cooling, that make them sort of hard to use. Unless you have a really nice chamber, seeing the actual trails can be difficult. I hit on the idea of using a nice fresnel lens for the viewing plane. It would magnify the interior of the chamber, allowing a viewer to more easily see the trails inside. Not only that, but fresnel lens are cheap, and can cover a large viewing plane, when compared to conventional convex lens.

So I hopped onto ebay and did a quick search for Fresnel lens. Of course I found some immediately, and as I hoped, they were nice and cheap. But that's not what excited me. Check this one out. See anything interesting there? It's a fresnel lens from a 3M overhead projector!

An overhead projector has all the optics, cooling fans (for the junction heatsinks), and plenty of space to house the chamber, the powersupply, junctions, etc. The viewing optics are perfect for this application too! The overhead lenses provide a great way to get really close with the trails, and the fresnel lens embedded in the top of the projector is nice an large, perfect for a big chamber. Also, overhead projectors are super portable, as most of them are found on carts.

Sometime soon I will be putting together an extremely small version of this cloud chamber, as the initial proof of concept. The parts are on the way, and as soon as ASS is complete I'll be digging into the Decay-o-scope.

Thursday, July 15, 2010

Parts (ASS)

Here's a couple of interesting things.

First, I was at radioshack, about to drop 5 bucks a pop on some crappy little relays, when a voice inside my head screamed out. "A dollar saved is two dollars earned!" At least, according to something I read on the internet about the subject ( I will try and find the link and post it here). Anyways, I quickly checked online and found the same relay for about .50$ so I scoffed at the radioshack employees and made my exit.

I got home and went to all electronics, and just as I finished my shopping list, I stopped and thought some more... I was on a roll you see... I thought, "Why stop here man? Why use mechanical relays when I am sure we can find some solid state motor drivers somewhere..." I started by googling some chips, but then I landed on this brilliant idea!

Sparkfun. I went to sparkfun, and located my motor drivers in about 3 minutes. Along with that I found a good graycode encoder, and some light sensors. Everything I need to finish this project! Not only that, but most of the stuff from sparkfun is centered around interfacing to the Arduino to begin with, making my work even easier (and more fun).

Here's what I bought:
Rotary Encoder $2.95 1 $2.95
Light Intensity to Frequency IC $5.95 1 $5.95
Motor Driver 1A Dual TB6612FNG $8.95 1 $8.95
Light to Frequency Converter - TSL235R $2.95 1 $2.95

Apart from this stuff, I saw tons of other tasty items for future projects.

Sparkfun, ftw!

Monday, July 12, 2010

ASS (Automated Shade System) Part 1: Mounting the hardware

ASS, as in this thing is a pack animal that carries the task of providing shade to my living room like a champ.

I came up with this idea after a couple years of owning a projector. I have lived without a TV for several years now and my only complaint with the projector has been the need for a shade (and the expense of buying new bulbs). Manual shades are find, but you need to find a good place to mount them, and they are often just left down which leads to dark nerd-caves where mold can grow in abundance. No, I would much rather have a bright and sun-lit area to live in when I am not using my projector. So began the birth of lazy man's shade.

A few features:
1) Automated, motorized
2) Activated by the projector
3) Feedback for shade position (so it doesn't completely unroll)
4) Ambient light sensitive, so it only lowers as far as it needs to
5) Easy to setup and install, easy to remove (I am in college, I move)
6) A cool project title (done)

So this project has been on my backburner for about a year. I was stuck for a very long time on what motor to use, how to fix it to the shade roller, and how to mount the whole thing. The sensors, and microcontroller were the least of my concerns. All those issues were solved when my roommate dropped a toyota window motor in my lap. It was perfect!

Next I had to get the motor attached to the shade. A bit of hobby cement and a grinder made quick work, and I had a perfectly easy shade-attached-to-motor. There is a circular metal piece in the window motor which slides into the main gear and is held by some tabs (sorry no pics). There are some bumps that need to be ground down, once these are gone I was able to cement the metal piece to the end of the shade spool. Bam! a perfect fit.

Making the mounting hardware was a bit more tricky. There are some nice screw holes on the motor enclosure which I used to attach the motor to some Lexan. The Lexan was then attached to a regular old bracket. Again this went very smoothly.

Now I have mounted the shade and motor to my wall in my bedroom which should allow me to mess around with it much easier. A good testbed. Hopefully I'll have some time to work on it this evening.