perestroika
@perestroika@slrpnk.net
- Comment on Don't let people sell you flashlights :) 1 day ago:
It sure is.
A typical “obscenely bright” LED chip might be Cree XML, but many similar chips exist. Then you need a driver. Some are fixed while some adjustable with a tiny potentiometer. You’d need an 18650 cell holder (it can be made too, an 18650 will go into a leftover piece of 20 mm electrical cabling pipe with a spring-loaded metal cap engineered of something).
Myself, I bought a nice head lamp, but it broke after one year. The driver board failed. Being of the lazy variety, I replaced the board with a resistor to limit current and now it’s been working 3 years already. Not at peak luminosity, the resistor wasn’t optimal of course. :)
- Submitted 1 day ago to diy@slrpnk.net | 8 comments
- Comment on ZFS High Availability with Asynchronous Replication and zrep 3 days ago:
Thanks, that looks like something I might have to try. :) Myself, over the network, I still don’t do filesystem level incremental backups, sticking to either directories or virtual machine snapshots (both of which have their shortcomings).
- Comment on ZFS High Availability with Asynchronous Replication and zrep 5 days ago:
I’ve been hearing about ZFS and its beneficial features for years now, but mainstream Linux installers don’t seem to support it.
Out of curiosity - can anyone tell, what might be blocking them?
- Comment on Raspberry Pi 5 vs Intel N100 mini PC comparison - Features, Benchmarks, and Price 2 weeks ago:
From a person who builds robots, three notes:
- Camera
Raspberry Pi has two CSI (camera serial interface) connectors on board, which is a considerable advantage over having to deal with USB webcams. This matters if your industrial robot must see the work area faster, your competition robot must run circles around opposing robots, or more sadly - if your drone must fly to war. :( On Raspberry Pi, in laboratory conditions, you can access the camera (with big ifs and buts) at 500+ frames per second. That’s impossible over USB and unheard of to most USB camera makers.
- Optimized libraries
I know that Raspberry Pi has “WiringPi” (a fast C library for low level comms, helping abstract away difficult problems like hardware timing, DMA and interrupts) and Orange Pi recently got “WiringOP”. I don’t know of anything similar on a PC platform, so I believe that on NUC, you’d have to roll your own (a massive pain) or be limited to kilohertz GPIO access frequencies instead of megahertz.
- Antenna socket
Sadly, neither of them has a WiFi antenna socket. But the built-in WiFi cards are generally crappy too, so if you needed a considerable working area, you’d connect an external card with an external antenna anyway. Notably, some models of Orange Pi have an external antenna, and the Raspberry Pi Compute Module has one too.
- Comment on Fifty Things you can do with a Software Defined Radio 📻 2 months ago:
I’m inclined to add:
51: monitor the radio spectrum for drones (and if they are hostile, warn people about them) - there’s a DIY recipe for a monitoring station out there somewhere, and some Ukrainian guys scan their sky with HackRF
SDR is definitely a technology worth learning.
- Comment on What's Up? 3 months ago:
Trying to figure out how my heat pump supposedly supports WiFi… in unfathomable and non-standard ways. It’s available as an access point, I can associate and ping it, but no TCP ports listen and no UDP port responds. Nothing cool, undocumented features down to the rocky bottom. When you buy a heat pump and plan to automate its use, check out supported protocols before making a decision. :)
- Comment on Gravity Storage 101 Or Why Pumped Hydro Is The Only Remotely Real Gravity Storage 3 months ago:
Yep. As for why:
- the material being raised and lowered must be very cheap (to be able to afford much of it)
- the material must be possible to automatically handle in arbitrary amounts
- the friction of raising / lowering the material must be low
- the handling should not require a slope of particular grade or a specific height
Trains fail the cheapness and arbitrary amount check, along with the slope grade check. Sand fails the friction check. Concrete blocks are close to failing the cheapness and arbitrary amount check. Cranes fail the specific height check for certain ranges of height.
Water… it also requires a certain slope grade, but the range is not narrow.
- Comment on Scientist Discover How to Convert CO2 into Powder That Can Be Stored for Decades 4 months ago:
Looks sound, but I’m not qualified to say if success will follow:
en.wikipedia.org/wiki/Sodium_formate
Upon modest heating, sodium formate decomposes into hydrogen and sodium oxalate. Shipping that somewhere where it gets converted back to sodium formate is the tricky part, because that seems unlikely to happen onsite (on a small site, anyway).
- Comment on €45,000 for a heat pump installation in Germany -- really? 5 months ago:
Why does the title link point to a BBC story about South Africa? :)
To answer the question - I don’t know.
For comparison: installing an air-to-air heat pump for a tiny house in Estonia:
- heat pump unit (smallest unit, maybe 3 KW heat output for 1 KW electrical input), bought at the deepest discount: 450 €
- physical installation (mounting on a rack on a wall) - DIY, 0 €
- electrical installation (running a cable to the outer unit and back to the inner from there) - DIY, 0 €
- sealing and letting the working fluid into pipes - technician’s visit, 100 €
I would imagine that an air-to-water unit costs more (the cheapest are probably over 1000 €, unless you use a pool heat pump which can be crappy), that an average German family lives in a far bigger house (so maybe 3 x more wattage), and that they need 3 installation technicians for several hours (maybe 1500 €).
Beyond that - profit?
- Submitted 5 months ago to fixing@slrpnk.net | 1 comment
- Comment on Not All Batteries are Created Equal | Hackaday.io 5 months ago:
Unfortunately, yes.
I’ve had multipe experiences with seeing a flashlight battery which, according to labels, ought to have the capacity of an electric vehicle cell. And of course they don’t. :)
If one needs high current, measuring the current with a known and low resistance (e.g. car headlight bulb) helps.
- Comment on Solar module prices may drop 40% to $0.10/W by end 2024 5 months ago:
As an anecdote, I can tell that I’m still using my shattered solar panels. :)
(Normal people would not, of course.)
One broke during welding because a droplet of molten metal hit it - the hardened glass shattered all over. Another met with a flying plywood sheet during a storm - the plywood went right through with a corner and made a hole.
I use both panels on a wheelbarrow to pump water on the field during flood season. They’re perfect, nobody wants to steal them because they look like they got nuked. :D I worry about the wheelbarrow considerably more. :D
But yes, a recycling plan would be needed. Grinding them up and getting the aluminum back is not too hard, but how to separate the glass from the sealing silicone and doped silicon - I know some folks in Korea do it, but I don’t know how. :o
- Comment on Is there any use of an end-of-life LED lightbulb? 5 months ago:
If it were just a straight glass tube, there would be potential uses (heat collector), but due to the curvature (cannot be stacked) and presence of mercury, nope.
- Comment on Design of zinc bromide flow battery 7 months ago:
No experience on that front, sadly.
Compared to iron redox flow batteries, it has about 5 percentage points of more efficiency (75 vs. 70%), slightly better cell voltage (1.8 vs 1.2 V) and better energy density per electrode surface (0.2 W vs 0.05 W / cm2).
The “resetting” of cells seems like a nuisance. Quoting Wikipedia:
Every 1–4 cycles the terminals must be shorted across a low-impedance shunt while running the electrolyte pump, to fully remove zinc from battery plates.[3]
- Comment on Weekly What's Up? 7 months ago:
Still building a DIY tractor / excavator - racing against time, as autumn is rainy here and you cannot weld water.
It can already maneuver, turn the mast, raise the first linkage of the mast, lower / pull the second linkage of the mast, but the excavator bucket is incomplete and the bucket tilting mechanism missing.
The remote control system is also missing (relays on a slow boat from China), so currently I have to control it via cables. Limit switches are missing, currently it’s unsafe to use for a careless operator. Later on, it will be remote controlled and limit switches will ensure it cannot break itself.
My own reason to choose remote control is convenience (better ergonomics as I can write pre-programmed movements). If it works too well, I might send a recipe to a friend in Ukraine, with the suggestion of asking around - maybe someone needs cheaper mine disposal machines.
Hydraulic excavators are neat, but too expensive for me, and require far too much power.
- Comment on Fix leaking kettle 7 months ago:
I would recommend motor silicone, since it’s often rated for 300 C. The surface should be scratched or sanded for better adhesion. After it has fully cured (several days), one should probably do about ten “test boils” to flush out anything that might seep into water.
- Comment on 40GW of solar panels gathering dust in European warehouses 7 months ago:
I think the same.
In the country where I live, thare are regions where the grid doesn’t accept new production capacity - because installed capacity covers local demand and electricity cannot get where it’s needed.
Also, planning is slow and permits are issued slowly - I have an acquaintance who created a semi-legal solar park because waiting for permits would take too long. Electrically, everything is fine, professionals wrote the project and did the job. The parish just wasn’t informed, only the grid company was. Since it’s a small park, it flies under the radar. :o
- Comment on I built my first shed! So proud of myself! 9 months ago:
Looks very nice and practical. :) Congratulations.
- Comment on Turning CDs/DVDs into a solar panel 9 months ago:
Or a solar concentrator and a steam / Stirling motor.
- Comment on DIY Wheels for Bike or Trike or Trailer 11 months ago:
Interesting project. :) When clicking the link, I was expecting to see CNC aluminum plates, but rebar didn't cross my mind. :) Cheap, doesn't require a skilled welder or good tools, and since it's steel, fatigue is not such a big obstacle. Rust will be an issue, though (solvable with zinc).