Inkplate Weather Display

Posted on 2022-10-19 by Nigel VH

A little while ago I ordered an Inkplate 10, which is a project pairing old Kindle E-Paper displays with ESP32 microcontrollers. Mine arrived a bit ago, and I’ve been looking for a good project to use it on.

Recently we’ve had some wildfires in the area that have significantly impacted air quality in our area. I have some air quality sensors here at the house, and all the data is logged, but I thought that this display would make a good way to present this data along with the time and some other data in the living room without having to check with my monitoring system.

The device was programmed using MicroPython, which connects to the wifi, pulls a json file from a local web server with all the data to present, and then handles all the drawing routines to display the info on the panel.

It was also interesting to experiment with partial refresh, which is a feature these E-Paper panels support. Partial refresh allows for updating only changed portions of the display without doing a full refresh of the panel. A full refresh involves some blinking between black and white and would be distracting every minute.

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Geiger Counter Kit

Posted on 2022-08-24 by Nigel VH

I recently saw that the MightyOhm Geiger Counter kit was on sale, and decided it would be fun to pick up as a simple, fun kit.

In terms of the kit itself, it was simple to assemble, and the instructions are well done. Easily less than an hour for folks who are familiar with soldering and simple through-hole component kits.

As one would imagine, I don’t have any specific need to be able to measure high energy radiation, but it’s an interesting sensor to have alongside my other environmental sensors including temperature, barometric pressure, humidity, and air quality (particulate counts).

I was however able to test to see that there was a slight increase in counts by placing some uranium glass marbles directly adjacent to the sensing tube.

I also feed this data into my general monitoring system so I’m able to graph this data over time.

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Measuring Mains Frequency

Posted on 2022-06-04 by Nigel VH

Mains frequency in North America is specified at a frequency of 60Hz, however in reality that number varies up and down a small amount as load and generation balance on the power grid.

As generation exceeds load, physically the turbines and generators will speed up and result in a slightly faster frequency. Conversely as load exceeds generation the extra demand will slow down the generators resulting in a slightly lower frequency. These changes are regulated and dampened by careful control of capacity, and the physical inertia of many many tons of spinning steel in turbines and generators across the grid.

These factors are part of a fine balancing act the grid operators manage, as they tune generation capacity to meet demand. Over the long term the grid operators manage these variations to average out to 60Hz, but over the short term we can measure these variations.

In the context of the significant power outages in Texas, some discussions with a friend inspired me to measure the variations in my region. In my case, I’m part of the Western Interconnection, which is not directly associated with the grid in Texas, so my data is not relevant to events there, but is generally interesting to explore.

I used an old wall wart power adapter with an AC output, and fed it into my frequency counter (which is referenced on a rubidium standard) and set up 1 second sampling intervals. In this case this is a view of about 1 minute of samples at roughly 4:30 in the afternoon. We can see load varying a bit over the minute, and overall load appears to be slightly exceeding generation as the frequency is running slightly below 60Hz.

Running slightly slow in the afternoon is not at all uncommon, as people use more energy during the day, and especially in the evening as people return home and start heating/cooking/etc. During the night typically generation will slightly exceed demand as people are sleeping, and bringing the overall average out to 60Hz.

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New Oscilloscope

Posted on 2022-02-25 by Nigel VH

For a number of years I’ve had some older analog oscilloscopes without storage capabilities, paired with a Saleae Logic, which has done well for my use cases in general, but there are some limitations. If a signal was faster than the Logic could capture, or not perfectly repeating to be visible on the non-storage analog scopes, it wasn’t something I could easily capture.

Recent years have seen a number of inexpensive but very capable entry level DSOs (Digital Storage Oscilloscopes) enter the market including the widely discussed Rigol DS1054Z.

I recently had an occasion to try and capture a very fast, but not frequently repeating signal in the phase comparator circuit of my homebrew GPSDO boards, and it wasn’t a good match for either my analog scopes or the Logic, so I took it as the impetus to finally pick up a DSO. The Rigol DS1054Z is a few years old at this point, and while there’s a firmware tweak to enable 100MHz operation, more recent options with a few years of advancement means that the Rigol is competing with newer, faster scopes, with more features in the same price bracket.

I ended up picking up the Siglent SDS1202X-E, which is a 200MHz, two channel scope. While I’m not any real reviewer, and am not going to touch the surface on the features, I will say I’m pleased with how it’s working. It was able to illuminate the signals I was interested in within a matter of minutes after getting it out of the box. I look forward to being able to get a better view of signals in my projects that I had avoided or worked around during testing in the past.

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Storage Expansion

Posted on 2022-02-08 by Nigel VH

For the last several years I’ve had a storage shelf attached to my home server supporting roughly 30TB of redundant storage making use of ZFS, which I’ve been quite pleased with. I use it to store all my various media, and back up all of my other computers to it. As part of my backup scheme I also back up some of the data from the array to a remote array in another location.

Unfortunately as the years have passed the data stored has grown and the array has been nearing full for quite some time. I’ve put off expanding the array as there’s always more pressing/interesting things to spend project money on, and a bit of a battle with myself about *really* needing more than 30TB of storage.

Finally a deal came along on disks that was too good to resist, and I ordered twelve more 6TB disks to complement the eight I had already. As is always the way it goes, this also necessitated changing out the storage shelf I had to accommodate the additional disks as well. Fortunately a friend was swapping some of their storage hardware at the same time and had some HP D2600 storage shelves they gave to me for a good price.

Racking up two of them, and plugging them in to my HBA was pretty quick and painless. After which comes installing all the drives, and configuring the ZFS pools.

With only a minor hiccup, in that ZFS needs the same level of redundancy for each sub-pool, I couldn’t add the new twelve disks as a new sub-pool to the existing eight. I needed to create a new, separate, ten disk pool, move the data over, destroy the old pool, and create a new sub-pool with the original eight plus the two left over from the twelve. With all that done I’ve now got a bit more than 80TB usable space and plenty of room for growth so I can forget about it for the next few years.

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