Spring Stormer Viscometer, proceeding, the board works.

Well, I recently recieved my boards back from ap circuits in Calgary and I’m pleased with the result. I kind of fucked up by ordering 4 of the same board and not 2 of the control board and 2 power boards. Oh well! I can use the current boards for the new ones. Anyways, here are some images of the board.


The two boards together, unpopulated and populated
The two boards together, unpopulated and populated

The board, populate with SMD's
The board, populate with SMD's

Rotational Viscometer design proceeding apace

It’s been a while since I’ve worked at full steam on the viscometer project. Though now a long way from it’s DIY roots I am making this new version from mostly Aluminum, Phenolic, Nylon and Low Density PolyEthylene. I had to scrap the last version since it would have been too difficult to actually assemble, this one is a little different in it’s overall size and assembly.


Of course it isn’t finished yet as it doesn’t have the screen and top switch attached as well as the outer shell. Perhaps I’ll start making it this week sometime.

New Viscometer board design and physical revamp.

Since my design was accepted in terms of moving ahead on a prototype, I’ve been working first on the board design. I have decided to abandon the PIC18F2620 in favour of the 18F4685. The reason for this change over is due to the fact that the 18f2620 doesn’t have enough I/O to handle the addition of two analog channels and four I/O for RS-485 communication.

This post is more for my own edification and to help me sort out my thoughts on this issue. I suppose for the sake of following my train of thought while sitting here, I’ll outline the specifications, as I think of them.

Overall feature set:
PWM output for 6-24V DC motor.
RS-485 Out – Rec enabled
LCD out
16 key keypad in
2 temperature sensors
LED indicators for power/error
Serial out for RS-232
Input for external reflection sensor
2 inputs for timing sensors

So, thats 1+4+6+8+2+2+1+1+2 = 27 inputs

I found some nice Molex headers that are single row, .100 pitch and is latched. Typically I use the friction based header and housings but it needs to be secure inside the housing and thus I’m trying out the new set. Also I’m going to use vertical out terminal blocks in order to save space inside the unit but not necessarily on the board.

I’m also considering adding an RS-232 port along side the board.

Hopefully this will be the final hurrah!

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.

Websites and registration, an opinion.

After a few years of looking on the web for various items, the trend towards mandatory registration on certain websites is becoming more and more prevalent. Now, I’m not talking about social networking sites or the really massive corporations, I’m talking about the mid-size companies that have their IT dude make them a site.

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.

Graphing program and viscometer proceeding apace

Well, things are proceeding apace as far as the viscometer is concerned. Unfortunately, the motor is just too non-linear to serve as a useful measuring device. God I’m dumb!

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
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!

Solid State Viscometer

Yesterday I started playing around with a solid state viscometer. This viscometer differs from other more physical methods in that it simply vibrates to determine viscosity. What I did was the following

  • Cut a strip of aluminum sheet.
  • Place a piezo tweeter element on each side
  • Tried to solder the elements to aluminum
  • Soldered two Teflon coated wires to the piezo material
  • Took the whole thing and cast it into epoxy as to seal it and make it rigid between the tow piezo elements.
  • Ground most of the excess epoxy off after curing.
  • hooked a function generator, sine wave, to one side of the unit.
  • Put the oscilloscope on the other side
  • Found the most resonant frequency, which in air, is about 62.5Khz
  • Tried ‘er out!
This is a closeup of the solid state viscometer prototype. You can see I had some problems trying to solder the unit to the aluminum.
This is a closeup of the solid state viscometer prototype. You can see I had some problems trying to solder the unit to the aluminum.
This is the solid state visc in the water. The Epoxy keeps it sealed from the outside and provides rigidity for energy transmission.
This is the solid state visc in the water. The Epoxy keeps it sealed from the outside and provides rigidity for energy transmission.

So far, it seems to provide useful results. I’ve tested it with water and oil. Oil tends to dampen the signal more than water which is a good sign since oil is more viscous but less dense, thus iy’s not functioning (entirely) as a densometer.

Here are the energy differences between water and air, the blue line is the sensor value.

This is the reading for the viscometer in the water. The blue line is the waveform.
This is the reading for the viscometer in the water. The blue line is the waveform.
This is the waveform out of water, the reading is the blue line
This is the waveform out of water, the reading is the blue line

Well, there we have it, a prototype vibratory viscometer. I guess the next step will be to do these three things.

  1. Produce a variable frequency.
  2. Amplify and use the signal appropriately.
  3. Produce a useful number.

Hopefully I’m up to the challenge. 🙂

Playing with simulations for the Viscometer

So, I’ve been playing with simulating the output of the viscometer at a specified power output. When the real unit runs it seems to output noisy but patterned values. I’ve found that the output has a sinusoidal output with anomalies at the upper and lower value ranges. So, I’ve made a simulation of the outputs so I can find the best way to smooth out the sample sets.

In my simulation I generate 2000 samples and divide the samples into 10 sets. These sets are each 200 samples, the amount that’s being generated on the laboratory viscometer. The idea behind this is to make all of the value sets almost exactly the same, so far, I’m close with the average, but not close enough.  Here’s a screenshot of the output

Viscometer Test output (click for full)
Viscometer Test output (click for full)

Green=minima

Purple=Maxima

Dark Green=Median

Pinkish=average

I’ll include a link to the file for shits and giggles (It’s freebasic BTW)

viscometer-timer-test