Working on the new rotary viscometer

Been working on a new version of the rotary viscometer, after many design changes, the result is this. A rotary viscometer bridged with a rotary reaction strain gage. Guess it’ll work. Here are some pictures.

I’d say a bit more but I’ll wait until the design is a little more fleshed out, and of course, remember that this design isn’t finished since the motor at the back obviously doesn’t float in mid-air.

Kinda been in a creative funk…

For the last while I’ve been in a bit of a creative funk. Troubles at work and the the weather have made it difficult to concentrate on the things that I like. Anyways, perhaps while I have some time off I might make use of it to do some stuff. Don’t know really.

That brings me to my next topic. What I should do.

Firstly, I think I’m going to start taking more pictures of Edmonton again and post them on Panoramio again. Frankly, this is the reason I started taking pictures in the first place was to provide images of Edmonton for whoever wanted to look and explore both the nice parts and boring parts of our city.

Secondly, I’ll finish that fucking clock. Really not much more to do it it, just make it so you can set the time.

Thirdly, focus on building a working vibratory viscometer. It’s the ideal way to measure Krebs units in an environment as harsh as paints and it will be substantially cheaper.

Anyways, End of Line.

Stuff about sensors, a quick post.

Well, I’ve been looking around at torque sensors and found some interesting information. For one though, they are NOT cheap. Keep in mind that these are higher sensitivity sensors but it doesn’t seem to have an overwhelming bearing on the overall price. for example.

Optical, high sensitivity sensor, ~$6000
Magneto-elastic sensor, ~$2000
Strain gage based, ~$4300

While this is expected, it’s still quite a cost on a per-unit basis. interesting.

Another little tid-bit I picked up is this.
Magneto-Elastic sensor document

Anyways, I’ll keep looking for a cheaper unit, though, I doubt I’ll find one cheaper than the unit I developed. Perhaps I’ll machine a small enclosure with precision bearings and develop a more robust and practical design. I have some conductive graphite for the brushes in order to reduce noise and the brushes could be replaceable. Might try it.

The LED Clock

Well, for the past little while, I’ve been working on a bizarre clock made with LEDs glued into a dollar-store cookie sheet. I got the idea just out of the blue and decided that it would be fun to build. Now, it’s nearing completion so I figured it’d be prudent to document the miserable contraption. I guess I should go through the steps it took to get this thing running.

First, I took one of those dollar store cookie sheets and drilled it through for 40 LEDs. 12 for the hours, 12 for the minutes, 5 for the seconds, 5 more for the div/5 minutes and five more for the outside and the PM light.


Drilling it wasn’t much fun but, when it was finished, I started to insert the LEDs with the grounds all towards the outside of their respective circle. Then I mixed up some epoxy and drizzled it over the backs of the LED’s. Unfortunately, the epoxy didn’t hold very well on the other epoxy surfaces so I used hot glue to tie them down.


As you can see, I labeled it in reverse of the other side so that I could get ‘er working. Thus started the long job of soldering the whole thing.


The image show isn’t the complete one, but it took me several hours to solder it all together. I used 7 groups of 6 LEDs in order to display the image. In this case I used the 7 groups for the duty cycle, thus a 1/7 duty cycle was used. Each of the 7 groups is fed ground through an MPSA13 Darlington transistor. Here’s a picture of the board that controls it.


Pretty fucking ugly, I know. But it works and I used an MCU (PIC18F4685) that was a little overkill but that’s fine, I’ve got quite a few of those. Anyways, so far so good, though it seems a little impractical as a clock and I think I set the rings of the minutes and hours too close together. Oh well.


Complete 180, well, perhaps 90.

So, after doing a bunch of work on the rotary strain gage it’s been declared incorrect. Oh well. Here’s the new concept, although not my own idea, were going to rebuild the entire concept around the notion of a dynomometer. First we’re going to place the motor inside of a housing that allows the motor to move freely with the help of large ring bearings, then we’re going to bind the motor in place with load cells.

While this concept may work, I feel as though it’s lower end repeatability and accuracy will be compromised and will be greatly subject to temperature differences as the bearings heat and cool from ambient and mechanical sources. But perhaps I’ll be proven incorrect.

Here are some images of the idea.

I’m going to keep working on my own sensor design in the meantime, it may come in handy someday.

Rotary Strain Gage update

Well, it’s been a little while since the last update, I suppose I should have stated something sooner. So far, the device seems to work but now I have mechanical problems. Friction on the top is preventing the load from being sensed at the paddles. Plus, the strain gages, I believe, are placed improperly. While it looks as though one side gets compressed and the other side gets stretched, I am thinking that this is not the case.
Unfortunately what that means is that the strain gages are counteracting each other, thus the voltage difference is too small to detect effectively.

Gonna design a new one with only two strain gages.

Viscometer Rotary Strain Gage update

It hasn’t been long since my last update about this thing but I’ve made some progress as far as making the unit into a single board. I simply used the AD7705B as I suspected it work work great for this application. I’ve been playing around with reducing the amount of noise coming from the sensor but random fields are causing the ad7705 to produce strange numbers, even when my hand just gets close to the unit. Here are some pictures of the unit.

Messy ugly board for rotary strain gage
Messy ugly board for rotary strain gage

Rotary Strain Gage being tested
Rotary Strain Gage being tested

Thus far it seems to work though, at least when tested with a multimeter. Sadly though, it seems impossible to test it with the oscilloscope because it uses the same ground as the power supply, damnit!

Minolta MD Lens test, 200mm Rokkor

A while back I purchased a 200mm f4. Rokkor lens off EBay for pretty cheap, like 40 bucks total. Since then, I haven’t really been taking any photos and thus haven’t been able to get a good feel for the lens. Tonight I decided to brave the cold and take some night shots with the camera, nothing special, just some far away downtown shots with lights incident to the lens.

Sony A300 with 200mm Rokkor lens attached
Sony A300 with 200mm Rokkor lens attached

As for the build of this lens, it’s all metal, including the built-in hood that slides nicely into place with a little satisfying click. The focus is smooth and the mechanics of it are pleasant. Even the grip is nice with its typical waffle pattern bezel. Very nice lens. However, reflections are a true pain on this lens, much like the other Rokkor lenses. I take night shots to test the lenses ever since I discovered the horrible properties of the Star-D 135mm f2.8 lens. This lens is not much different with internal reflection galore. Granted though, I haven’t really put this lens through its paces as yet and these two scant images are hardly a definitive test. Anyways, here are two of the shots I felt could grade the camera decently.

Night Shot with 200mm Rokkor, Level corrected
Night Shot with 200mm Rokkor, Level corrected

Tree shot with 200mm Rokkor Lens
Tree shot with 200mm Rokkor Lens

As you can see with the downtown image, it’s level corrected, the wind was so strong that long exposures tended to make the focus look poor, when in fact it was shaking. The tree image is also level corrected, just to give it more contrast, I did not, however, sharpen the image.

Anyways, these are obviously poor tests but can serve as a bit of a guideline as to what to expect from these lenses. Another issue is the MD adapter, I’m not entirely sure that either adapter that I have access to is appropriate for these lenses. I’ll do more tests later.