New cables

I made some new cables (the ones on the right). They’re banana plug to square socket. They complement the ones on the left, which are banana plug to pin jumper. The pin jumpers can plug into the square sockets.

I also installed the two black hooks to hang them on. The silver hook with the hot glue gun on it was already there.

For each type there are two pair of short ones and one pair of long ones.

SPI: The serial peripheral interface

Watched this one from Ben Eater: SPI: The serial peripheral interface. I found it while watching this one: Hacking a weird TV censoring device, which was kind of hilarious, he reverses a profanity filter and finds its dictionary.

I noticed Ben Eater has a Keysight DSOX1204G Oscilloscope, a pretty nice looking bit of kit. Oh dear, he also seems to have a Keysight DSOX4024A Oscilloscope, which is an even nicer looking bit of kit.

When I have some time I’m gonna get some of these BME280 knockoffs and see if I can play along with the SPI 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.

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.

Measuring Input Impedance of MSO5074

Over here I asked about the measurements I was getting when I tried to measure the input impedance of my scope with my multimeter.

I was getting a reading I didn’t expect or understand, but that turned out to be because of a dud BNC to banana adapter that I was using.

For some reason this adapter had either a 1.5 MΩ or a 6 MΩ resistance across it. It would change from time to time when I plugged in banana plugs. Weird. I can only assume some sort of manufacturing problem.

I threw the adapter in the bin and measured again with functional equipment and got the reading of 1 MΩ that I was expecting.