Messy ugly board for rotary strain gage

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!

Sony A300 with 200mm Rokkor lens attached

Night Shot with 200mm Rokkor, Level corrected

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.

Here’s what it looks like so far:

The rotary strain sensor

I’ve put it through its paces thus far and I can see a 10mV difference when I move the sides, that’s good enough. Soon I’ll see if it works with the stuff attached.

Nowadays if you want to find any kind of information on the product a smaller company makes, you have to register for an account on their site even for things like datasheets. While on the surface this seems like a good idea, since you can engage the person in setting up an account on your site and have their e-mail address for later, it is irritating at best. Unfortunately, companies take it so far as to require you to register for almost every thing under the sun. Things I’ve seen required registration for:

• Product Pricing
• Data Sheet
• Frequently asked questions
• Their forums (Not to post, just to see their forums)
• The products they make!?!?!

Like I said, I can see the logic to it in terms of engaging the browser, however, myself I find myself backing out of the page, even if I need the information when presented with a ridiculous registration prompt. I’m fairly certain that other people do the same thing when looking for a product. Especially when looking for parts. There are so many manufacturers of similar parts and when you have to go from site to site and fill in a billion fields of data just to see what they fucking make is absolutely ridiculous!

All I can say is this. STOP REQUESTING REGISTRATION YOU IDIOTS!

In the end they only increase the traffic on their phone lines with engineers and designers that simply want some damned information. Stupid.

Note that these aren’t all of my drawings, but a decent selection of them.

Torque Coupling

It’s pretty fucking ugly but it’ll work for the time being. I did have the ribs that sit under the sensors quite a bit thicker, but there wasn’t enough strain to be useful for measurement, I had to hacksaw the chunks underneath right off.Unfortunately, I believe the polyurethane glue I used has caused strain on the sensor as it cured, I don’t know of it will go any further.

So, I’ve started on the circuit as of yesterday. I have it set up to take the PICKIT2 interface so that I can hot-program it and I setup the serial out board so that I can output debug data. This works thus far. Soon, I’ll be setting up the ADC and attempting to interface with it.

Starting on the ADC circuit

Here is an image dealing with the read/write cycle on the AD7705, also to note is that the AD7705 is MSB first.

The timing for read/write on the AD7705

Here’s the site they came from http://www.protongeeks.com/index.php?option=com_content&task=view&id=63&Itemid=27

Anyways, I’m glad to have my equipment back and ready for whatever crap I decide to build. Here’s a picture for posterity:

My bench as of Nov, 2008

Anyways, I’ll attempt to update this as much as possible, for whoever is interested (or not).

Strain Coupling Model View

What you can’t see is that I plan to manufacture it out of plastic, that way the strain gage experiences the most out of the deflection of the part. I’ll use a flexible polyurethane bonding agent for the strain gages, allowing the forces of the strain to work without breaking the bond.

Here’s a through model view:

Strain Coupling Transparent View

Of course, it only took me a few minute to make this model but it helped me see if what I was doing would work, I also used FEA to see if the forces would be transmitted where I wanted them. The FEA results were promising, nice even strain along the gage surfaces. (Those gauge surfaces are seen in light blue). You can see though that the hole through the side relieves some strain on the strain area, though, this shouldn’t be an issue.

Strain Coupling Strain Test view

Here’s an image of the stress as calculated by Cosmos

Strain Coupling Stress Test view

Well, hopefully this will work. First I need to get the strain gages to provide reliable results. By using two of them, temperature concerns should no longer be an issue and should help mitigate innacuracies. I’ll post pictures of the finished part, though I don’t think I’ll do it on the NC, I’ll just do it manually, it may look like ass

Anyways, my graph-it program is working ok now and producing some useful graphs. I have programmed the save and load features and they seem to work just fine! It will eventually allow for a variety of data analysis techniques.

Here’s a picture of the linearity, or lack thereof.

Reciprocal of motor linearity

The blue at the bottom represents the overall error , the pinkish is the actual reciprocal of the tach values and the brown is the average of the tach values.

Hopefully I can get this working… Sigh!

Anyways, I’ve been running tests with the viscometer and everything is working great so far. I’ve got the temperature sensors working and the conditioning of them with OP-amps has worked like a charm. Though I find that the read value from the ADC is pretty jumpy.

Anyways, as reference, here some photos.

The Whole Deal

Temp Conditioner

Motor Linearity