Steve’s Junk

What’s an abraser you ask? Well, it’s a device that has two abrasive wheels that are pressed against a plate with paint on it. The idea is to determine the wear a certain coating or paint will get with a number of revolutions on this device.

Anyways, it was acting up the other day and the guys at work asked me to fix it since the numbers were jumping into the thousands quite quickly. Since this device counted revolutions via an interrupted beam of light, I simply stated that it was dirty. I was right, it was just a bit dirty and after blowing the head out and looking at the signal, it was fine. What surprised me though was it’s electronic construction.

Surprisingly it was nothing more than a PIC-based protoboard with a transformer and a gearmotor, I was surprised that it was so sloppily put together. Here are some images of it in case anyone is interested or in case I wish to refer to them later.

A shot of an (older?) Taber Abrader

This is the inside view of a Taber abrader

As is evident, they used a PIC16C71 for their little project and soldered it together on a protoboard, very strange for company that’s been in business for so many years. They even used cables that didn’t have the correct number of wires in them, they simply trimmed the excess wire, sloppy!

I was perusing about today and found a helpful document about OP-Amps. It’s distributed by Texas Instruments and it looks really good even though I haven’t read it for the most part. You can get it here:

http://focus.ti.com/lit/an/slod006b/slod006b.pdf

Or you can download from my site, just in case it got flushed down the digital void somehow.

opamps-for-everyone

Have fun!

Well, I’ve been thinking about deleting the gallery that’s been installed since I started this site. So far I haven’t even paid any attention to it since it recieves very little traffic and frankly, I don’t pay any attention to it.

I was thinking about deleting it… Instead, I’ve decided it’d be better to revive it, keep all the images that are on there and use it as a backup for all of my raw images. I’ll keep anything sacred close to the chest but other than that, I’m gonna make it public.

So, http://smackaay.com/gallery/

I’m going to start uploading sets of images, slowly but surely, as to avoid bandwidth charges!

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 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 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.

Well, I took the plunge and built an RS232 output device so that I can track the values over a longer term than whatever my memory can hold. I’ve started with a series of tests designed to test the speed control or the encoder. So far my results have been poor. I’m not exactly sure why, perhaps the motor is hooped, maybe the encoder or perhaps even my logic with timing the pulses, I don’t know as yet. I’m going to purchase some different motors to try out.

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Click on the pictures to enlarge them, there is a good description of each. There is also a zip file of the analysis data and the program so far.

viscometer-data-analysis-081009

For a while I’ve been looking for a decent freeware terminal program. Oddly enough, it’s been sitting right under my nose through a simple google search. I figure I’ll record it here for my own edification and file storage, just in case I can’t find it again…

realterm_20057_setup

Later tonight I’m going to try and post some of the results of the tests from the viscometer. So far, not so good.

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)

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

I purchased a lens off Ebay to test out. It was fairly cheap, like $25 all told and it looks great and feels great in the hands. I’ve taken a few test shots with the lens and I’ll post them here if anyone is interested in seeing what this older 3rd party lens is/was capable of.

Here’s the lens in question.

135mm F2.8 Star-D Minolta MD lens (click to enlarge)

Here are some shots from the lens. I’m not going to edit them in any way. This is how they came off the camera. Sorry ’bout the extra shot of the lens, the gallery doesn’t allow removing images, weird.

So far it’s a really nice feeling lens. The aperature ring opens and closes smoothly and the focus bezel moves like a dream. It’s gonna take some getting used to, but I don’t mind manual focus too much.

Well, as far as viscometers go, I could be considered an expert by now (no, not really). Today my new board arrived and I assembled it, I’m kind of proud of it, it works real slick just like the last one. This one has the following changes

• ICSP provisions so that I can program it in place.
• a PIC18F2620. Has 10 times the program memory and RAM.
• diode protection in case the power is hooked up wrong.
• Fast recovery diode for motor induction absorption.
• Larger traces for the motor.
• Fixed resistor array.

Anyways, here is a comparison shot. Old on the left, new on the right.

click image for large size

Well there you have it!

I suppose I should post a picture of my new office. Despite the fact that nobody reads my blog, I’ll post a picture for posterity.

Office at Endura

Pretty fucking messy, but that’s me!

I’ve been looking around at various themes for wordpress. Being a fan of simple, straightforward designs, I picked Block2.

Persoanlly, I like it better than the previous one, it’s very nice though I may change it over to some sort of fixed width font.

Here’s an interesting audio tidbit I found about the US mortgage crisis. Well worth a listen (click “full episode”)

http://www.thislife.org/Radio_Episode.aspx?sched=1242

Listen, very informative.

So I’ve been working from home for a while and now I’ve moved all of my equipment to my place of work. I’ve been given a new office to work from and it seems promising so far. I’m also going to revamp my site a bit. I’m not certain as to wether or not I want to keep the gallery intact or use it as a backup server for my images. At this point, I’m not entirely sure.

So, hopefully I can get some stuff done this winter and continue riding well into december. Let’s hope so I guess…

After a couple of weeks of solid work, the laboratory viscometer is almost ready for extensive testing. Since this is a redesign and simplification of the older design, it has a few more features and a couple of drawbacks in relation to a brand name Stormer Viscometer. I’ll detail some of the features and drawbacks.

Features:

• Viscometer can produce results in both KU and MPa*s.
• Viscometer can be used as a gel timer.
• Viscometer can derive a trend plot of viscosity over time.
• Current design is highly simplified, requiring only a 2.25″x1.875″ circuit board and an appropriate power supply, this allows it to fit in smaller, potentially hand-held units.
• Has an easy to use menu system to allow lab techs to calibrate the unit themselves and operate it easily.
• Has a keypad for data entry, used for time lapses and calibration (Oil values)
• Relatively cheap to produce.
• No spring to break, unlike the Stormer viscometer.

Drawbacks:

• Unit does not do live sampling, thus, any kind of watch-and-wait testing has to be done by the computer. This is due to the fact that the motor has inherent changes along the time line and therefore a fix sample time is necessary.
• Unit is a single CPU unit, unlike the larger in-process version, thus requiring a great deal more finesse in programming.
• May still be difficult to detect low-viscosity fluids like water and alcohol. Different motor may make the difference.

Things to do so far:

1. Finish motor mount - almost done anyways, need encoder though, hence why I’m using the in-process viscometer device for now.
2. Test and program - of course, who know how long this will take, though, the majority of the difficult work is already done.

Some pictures (click to see larger!):

Since the last report done on the viscometer, a great many things have changed in regards to the mechanical and electrical design of the unit. It is now a rotary viscometer instead of a paddle based unit. It operates in a similar fashion to the typical Stormer viscometers in that it measures the energy required to push a paddle at 200 (or other specified) RPM; the greater the force required, the larger the KU value.

Summary of what’s been done so far

So far, the majority of the unit is in a functional state. Recent modifications have allowed the unit to function in a more reliable fashion. The unit works on the following principle:

• There is a gear motor that is specified to run at 275RPM at full power.
• The motor’s shaft is fitted with an encoder.
• The motor is started and operated with a PWM (Pulse Width Modulation) output.
• If the motor is running too fast (>200RPM) , the duty cycle is dropped.
• If the motor is running too slow (<200RPM) , the duty cycle is increased.
• From the duty cycle values sampled over a period of time is derived a viscosity value, preferably translated into Krebs units.

So far, things that are done/workable are:

• Main CPU w/o calibration and safety routines
• Tach Controller
• PWM Controller
• High ESD Input controller
• Auxillary controller (not implemented yet)
• Motor controller
• Main Viscometer Unit

Here is an image detailing some of the items on electronic side of the viscometer:

Click to enlarge

The Viscometer Electronics

Whats going on now?

Currently, I’m working on a few items related to the viscometer, namely:

• Viscosity testing with mostly a flour-water mix since the resulting mixture is similar to the shear thinning fluids of paints and coatings.
• Explosion proof case acquisition. While there are a great many NEMA-7 Enclosures available, I’m trying to find one that isn’t $800+ per case.
• Algorithm changes. Since the samples that come into the unit are not as clean as they appear on the screen, the sampling algorithm has to be tested in order to produce accurate and useful data to the automation system.
• RS-232 Output device. I’m currently working on the output portion of the device, that way the automation system can read what’s being measured.
• New Mainboard
  

  New Viscometer board

  This board integrates everything that you see in the picture above and allows it to take on the same footprint as the 5×3 power supply. This allows one to purchase smaller enclosures and it’ll be a lot more reliable with fewer interconnects.

Some Problems

While there aren’t any showstopping problems, there are a couple of kinks to work out.

• With the increased friction from the new top and bottom bushings, the sensitivity to the lower end of the scale (around water’s viscosity) is almost Nil. I’m going to play around with the sizes and try a couple of tricks in the way of selectively modifing the outgoing voltage. The bushings are a double-edged sword, they help remove the reliance on the alignment of the shaft and the unit in general but, of course the aforementioned friction is now a problem.
• Long warm up times. In order to reach a stable set of samples with any fluid, the unit must be on  for at least 5 minutes. This has been exacerbated by the bronze bushings to about 7 minutes. I suspect this isn’t the fault of the motor but of the seals and lubricant needing a warm up time in order to drop their friction levels. I am looking at different lubricants and at adding a start up routine that runs the motor at full speed for 40 seconds or so, this seems to mitigate the issue.
• Still some measurement differences based on vertical or horizontal alignment….

Well I hope this was informative, if you have anything you want to ask, feel free to do so.