I see Orange Pi in my future. Also of interest: LinkStar H68K. Learned about them over here: I Can Save You Money! – Raspberry Pi Alternatives.
Orange Pi
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New shelf
So I installed this shelf. It’s the black wiry thing:
But it was a bit of an ordeal. I managed to snap not one, but *two* screws while bolting it in.
The drill bit on the left was a casualty of trying to repair the mess. One screw shaft was irredeemably stuck in the wood, I couldn’t get it out. The other one I needed to drill around to get it out, it was stuck hard. Then I just plugged the hole I had created with craft sticks and hot glue, then tried again.
The spirit level says I did a fairly reasonable job of it:
Software optimization resources
At last! A website that looks worse than mine: Software optimization resources.
The above resources were referenced from an article I read today: The World’s Smallest Hash Table. Also mentioned were Integer division by constants: optimal bounds and the Avalanche effect.
In cryptography, the avalanche effect is the desirable property of cryptographic algorithms, typically block ciphers[1] and cryptographic hash functions, wherein if an input is changed slightly (for example, flipping a single bit), the output changes significantly (e.g., half the output bits flip). In the case of high-quality block ciphers, such a small change in either the key or the plaintext should cause a drastic change in the ciphertext. The actual term was first used by Horst Feistel,[1] although the concept dates back to at least Shannon’s diffusion.
Weight loss
So here’s my weight loss since December 2021 in relative and absolute terms. The graph is the 7-day moving average. Still a long way to go!
“Clean” Code, Horrible Performance
Today’s viewing: “Clean” Code, Horrible Performance.
All You Need To Know About HDMI
This one, also good: All You Need To Know About HDMI To Fix Stuff! – Port Broken No Video Picture Output Repair Replace.
In it I learned about LVDS.
There’s some interesting Fluke equipment to check out.
There’s a follow-up video here: All You Need To Know About HDMI To Fix Stuff – Reprise. How To Repair Broken No Video.
All You Need To Know About ESR METER
Enjoyed watching this one: All You Need To Know About ESR METER To Fix Stuff. How To Use Test Capacitors Inductors Short Finder.
Mentioned were:
ESR stands for Equivalent Series Resistance. You can measure it for capacitors and inductors.
In the video the presenter makes this note: capacitors with these symptoms: double rated capacitance and low ESR, will exhibit very high DC leakage current. He says you should always measure capacitance and ESR when testing caps.
The formula for measuring microhenrys with a 100 kHz ESR meter is: R = 0.628 L; where R is in Ohms (Ω) and L is in microhenrys (µH). So if we measure the ESR we can calculate the inductance.
In the back end of the video he explains how to use an ESR meter to find shorted out MOSFETs in the power stages on a motherboard.
How DC Clamp Meters Work
I watched this fun video: How DC Clamp Meters Work (And other ways of measuring electric current).
The DANGERS of Inductor Back EMF
Watched this one today: EEVblog 1409 – The DANGERS of Inductor Back EMF.
I learned about back EMF, freewheeling, snubber, flyback, or clamping diodes…
In this video I also learned that BPJ transistors have a storage time, or switch off time, in the order of microseconds, e.g. 5 μs. That probably explains what I saw when I tried to measure the frequency response of my DTL OR GATE.
Ground Channel Coupling
Over here I asked about ground channel coupling because I didn’t understand how it could be useful.
All it does is tie the channel input to ground. But it doesn’t do that by shorting the channel input, rather it just substitutes the probe input for a ground input.
Apparently this used to be useful for calibrating old CRO scopes. You would set to ground channel coupling, set ground where you would like it on your cathode ray tube, then set back to either DC or AC coupling.