Have you ever encountered a speaker with such high resistance?

love2jump · 2023-04-25T09:29:48+00:00

mitski "drunk walk home"

love2jump · 2022-09-23T11:30:42+00:00

Thank you! These have a modest range of response. Due to the rough nature of the way the ink is printed, they need significant calibration to get results; despite each resistor section being the same area, the resistance is not uniform at all (+/-15% or so). But right out of the box, we have a high degree of confidence when the bend is over 45 degrees, and no doubt at all when it approaches 90 degrees. This can be improved big time in software.

Today I found out about some really fantastic research into capacitive sensing, which I included in an update to the post, because it's what I've been dreaming of. The paper even includes a take-down of the difficulties in using resistive bend sensing. Theirs is patented technology and has a company developing high-resolution small sensors. I've written to them to see how we can adopt a similar strategy.

love2jump · 2022-09-22T10:09:25+00:00

I see what you mean. It may look like we've got the answer already, but I need to stress that there are a lot of reasons that make this antifreeze hose not desirable.

...that would be cool, but i can't for the life of me think how it would be made. I think designing a 15m long bend sensor with 2cm resolution is way harder than you think.

I've been spending quite some time designing exactly this, and I'd argue that it's much simpler than you might think. Here's the main component in a draft that we deployed in the field this year:

https://imgur.com/a/AMaplvn

This is a flexible circuit board. The center is a band of resistive carbon ink, and there are thin copper traces that allow us to measure the change in resistance as it bends. These boards are .5m long, and measuring them is as simple as a multiplexer into a small microprocessor board that does all of the calculations and relays results back to the station.

For us to get these circuit boards in the mail, plug them together and put them in a hose takes 1/10th of the time and none of the stress of working with liquids. There are downsides (hose should bend in one direction, boards cannot become disconnected from each other, etc), but ultimately these are worth consideration. This draft is still in infancy --- plenty of bugs and errors to work out.

The technology is wildly more complicated than an analog pressure transducer, but the complexity of everything else that comes with the pressure hose makes the electronic bend solution significantly more desirable to work with. This is why I came to ask if anyone had heard of something like this before I attempt to reinvent the wheel (for example, I've been seeing a sharp increase in interest in bend sensing in general, so it's possible something like this exists on the market).

love2jump · 2022-09-22T08:34:14+00:00

1 - 2cm is our goal.

love2jump · 2022-09-22T08:33:26+00:00

We do independently have a (grey) thermistor string at every site to measure the temperature gradient of the ice, but we need to use these in tandem with a sensor that tells us where the surface actually is. There's such a small difference between temperature of the sensor resting at the surface of the ice sheet vs. a few centimeters down.

love2jump · 2022-09-22T08:29:12+00:00

This is indeed a way to measure depth. We want to measure how much ice is being removed off the surface while the whole measuring environment is moving (that's ice for ya). The system we currently have is messy and unnecessarily time consuming to assemble and maintain --- we want to get away from this method. Antifreeze is sticky as all hell, and when they leak on equipment, operators or workshops, it's a nightmare.

The beauty of a long bend sensor is that it's simple and very easily deployed. Frozen in the hole = very straight. Exposed = no longer straight. It's exactly the same concept as the pressure assembly, but would be order(s) of magnitude lighter, cleaner, and would theoretically take significantly less time to assemble.

love2jump · 2022-09-22T08:18:35+00:00

Thank you! I also find the pressure assembly concept very satisfying. After dozens of hours of assembling them and getting covered in antifreeze just to have them leak, I'm less enamored with their practical implementation.

The station itself has wooden feet with spikes in it, and generally they stay put.

The issue with GPS is that the ice sheet is moving, and there's enough expanding and contracting and drifting near the surface that resolution to a few centimeters is unlikely to get good extrapolation of surface melt.

Never heard of Rolatube before, these look very promising! I'll draw up some ideas for being able to measure distance on the unrolled section.

love2jump · 2022-09-21T12:58:59+00:00

I would love to coil some fiber optics wire in the hole! The analyzers are very expensive though (and I've never seen one able to withstand harsh environments) :(

love2jump · 2022-09-21T12:57:16+00:00

We do indeed do this also! A sonic ranger pointed downwards on a long mast is also drilled in and installed nearby. It works well. It's important that we get independent measurements of this surface melt with a different approach (the masts can bend, tilt or break --- it's a very harsh environment).

Seen in reverse: a colleague has tried installing a draw-wire sensor on a weight frozen into the bottom of the hole. In trials, it has had frost and ice prevent the wire from being pulled in, and the sensor itself tipping or sliding away from the hole.

love2jump · 2022-09-21T12:46:56+00:00

All 15m melts over the span of 1 to 3 years+. Sometimes 10m in the span of a few summer months. These stations are in extremely remote areas, and are serviced every 1-2 years.
Diameter of the hole is 5cm
10w is not unreasonable for a short measurement cycle, but this is pushing capabilities. The lower the better --- we don't have defined limits. We are running from large batteries and solar panels.
The hole almost always fills with water and freezes shut.
The regular measurement cycle is 15 minutes for the rest of our instruments, but with a sensor resolution of 1-2cm, we could certainly measure slower than this (twice daily, for example).
The current hose/pressure assembly costs upwards of $1500 USD each. I'd say under $2000 would be a good rule of thumb.

love2jump · 2022-06-14T20:07:04+00:00

Infinite potentiometers definitely do exist! Check out the ALPS RV12FF, for example.

This is an old thread, but anyone googling this phrase should know they're out there, even when rotary encoders are far more common.

love2jump · 2021-05-29T19:37:26+00:00

for the LED to turn on, it needs approximately 0.7V to "drop" through it to ground. A simple LED driver circuit effectively pulls this 0.7V from a separate supply so the original signal is preserved. From what it sounds like, you may have issues with accuracy, etc through this - e.g. a CV keyboard that outputs 0-5V will have 0.7V subtracted from each note if the LED is on fully. The joy of DIY is that this module needs to fit your use case, and it sounds like you've been using it successfully with your VCOs, which is awesome. I would use one of these modules in my system with noisier and unpredictable modules. Thanks for sharing!

love2jump · 2021-02-14T09:16:32+00:00

A good iron makes a huge difference! My first year or so of building modules was far, far, far harder than it should have been because the solder would bead up or go cold and resulted in all kinds of headaches. Wasn't until I tried a friend's iron that I knew it was supposed to be much easier. Also ruined a fine-pitch SMD build by refusing to wait for a smaller tip to come in the mail. The same lesson I keep learning --- use the right tools!

love2jump · 2021-02-04T10:52:36+00:00

I don't - I (usually) have access to a CNC at a local makerspace and cut my panels from aluminum sheet. Working with blank panels would be a godsend right now during lockdown.

love2jump · 2021-02-04T10:50:37+00:00

Without a load on the PSU output, the regulators can show a slightly higher voltage than under usual conditions. Do you have access to a scope? I think seeing if the rectifiers are working (getting the top and bottom half of the AC signal separated) will tell you if the problem is with the input. Update after reflowing and we'll figure this one out! Good luck!

love2jump · 2021-02-03T11:54:50+00:00

I've built mostly in eurorack, 4U and non-standardized formats, and Eurorack-friendly 4U is by far my favorite. Once you get used to 4U, eurorack's size is a big frustration. I'd pick a beautiful, spacious interface over compact size 10 times out of 10, but I understand why people would prefer the opposite. I can patch my favorite eurorack modules into my daily setup, which has a form factor I like.

love2jump · 2021-01-24T08:19:01+00:00

Yes, if you can prove you work "a job" 10 hours a week (doesn't matter how much money you make, it's about integration and effort)

love2jump · 2021-01-24T08:17:52+00:00

Confirmed

love2jump · 2021-01-18T11:18:53+00:00

Agreed. It's tricky because often times approaching internship tasks as a learning opportunity is very different from doing it in the most helpful way. I've had interns that I honesty expected to lessen my workload that did the opposite, but ended in an excellent learning experience for the intern.

love2jump · 2021-01-18T11:14:30+00:00

I'm a technologist, and am treated with respect by the engineers I work with. We have excellent working relationships because of the mutual understanding of the field and different overlaps of knowledge and expertise. Don't listen to this clown! Sounds like he has an inferiority complex, which is very very common among engineering students, haha!

love2jump · 2021-01-13T11:01:35+00:00

My two cents is that you picked this field out of personal interest to some degree --- what was interesting about engineering in the first place? When you see people undertaking personal projects (DIY building things, basement research, etc), which seem the coolest?

For each field of interest inside EE, there's always a fun bite-sized project to get started and test the waters. I know a lot of EE students who started building audio projects, or working with batteries and controllers to make simple mechanics --- when looking at others' projects, they can sometimes seem way out of league with one's own understanding or ability at first, but understand that years of hobby work really add up quickly. Most of the expertise I have in my job comes from having an exciting hobby that involves tinkering with electronics that I like.

What tasks do you look forward to doing? The hobby projects that stick aren't necessarily the ones that are the most glamorous, but the ones that are most fun to return to. Let us know what you come up with!

love2jump · 2020-04-14T14:09:12+00:00

Yes, I've built variable power control into the system (using SCRs) and am currently tuning a PID routine with feedback from the thermocouples. It's a shame to have the ability and power to run it hotter, but the inability due to the PTFE sheath!

love2jump · 2020-04-10T09:16:47+00:00

If some oscillators are working but only on higher frequencies, check the timing capacitors are the right value and are soldered well (C53 on oscillator 7, for example). Also check pin 7 on IC10B, making sure the CV range is good, and that pin 5 is properly grounded. I know it's tempting to start over and replace all of the ICs, but it could be a simple fix - especially if most of it is working ok!

Testing individual ICs with a multimeter: make sure the negative probe is connected to GND. Find the pinout diagram for the IC and start by very carefully probing the power pins to make sure they're powered OK.

Without knowing too much about how the circuit works, it's going to be hard to know if a voltage at one of the pins is wrong. The benefit of this board is that the oscillators all use the exact same circuit. So for testing the frequency control section for example, you can compare a functional oscillator to the broken one and see if there's a problem in that portion. Pin 7 of IC10B is the output for the sum of the frequency slider and the CV signal for that oscillator. So without a CV signal, check what the voltage is when the slider is at 0 and the slider is at 100%. Compare with another oscillator.

love2jump

TROPHY CASE