Recent Posts

1

Embedded Computing / Re: For how long can be held back a Linux kernel, yet upgrade to a new distro?

« Last post by magic on Today at 04:48:07 am »

Unless the special snowflake driver is strictly required for boot, I think I would first install normally, then make sure everything works as expected, then downgrade the kernel and check if it still works.

Also, do you have sources to this driver? Any chance that the "incompatibility" is as simple as an explicit version check?

2

General Technical Chat / Re: Whats your Work-Bench/lab look like? Post some pictures of your Lab.

« Last post by pqass on Today at 04:45:32 am »

That was nice.  Too bad your gear acquisition syndrome is only going to get worse.  Seek help before it's too late.   

3

Projects, Designs, and Technical Stuff / Re: Opamps - Die pictures

« Last post by iMo on Today at 04:39:15 am »

Have you ever shot a chopper opamp?

zeptobars: Microchip MCP6V27 - auto-zero opamp

This is the only example I have seen so far..

That is not linear analog technology anymore .. Compared to the traditional opamps it is perhaps 1000x more complex structure..

4

Beginners / Re: Why is there distortion in my Clapp Oscillator?

« Last post by BlownUpCapacitor on Today at 04:33:03 am »

L2 is floating at DC.

Unsure by what you mean, for me the oscillator works just fine in LT-spice, except the wave is not sinusoidal.

Maybe it's because of the different varactor I used? I'm 96.7% sure the varicap I have is the KV1236Z.

5

Repair / Re: HP54600B with spike problem with and without signal

« Last post by sacha on Today at 04:30:28 am »

Hi, thank you for the reply, in fact as soon as I turn it on the signal is very dirty and after about 15 minutes it disappears on its own. I tried to check the voltages coming out of the power supply but I didn't see any ripple and the voltage is around 5.10Volts. However, I noticed that if I cool the U33 the spikes return, perhaps it could be this integrated circuit or the timing of the signals is incorrect

6

Projects, Designs, and Technical Stuff / Re: High reliability ribbon cables

« Last post by thermistor-guy on Today at 04:20:08 am »

...  Out of 1726 in the field for <2 years, 78 have had intermittent connections and were replaced.  The application is not challenging, clean, dry, low vibration, low stress and no movement...

I use 3M twisted pair ribbon cable with Harting IDC DIN41612 connectors (64-way), in  test jigs. The combination has proven reliable, but there is a fault that
can occur during initial cable assembly.

The cable can sometimes have a distorted conductor-to-conductor pitch, so that it doesn't line up exactly with the IDC connector tines.
If the misalignment is bad enough, it results in adjacent conductor short-circuits.

Conceivably, if the misalignment is not that bad, but still present, it could lead to unreliable conductor-to-tine contacts; contacts that are not
gas-tight and that will fail over time.

To guard against this, I check the cable alignment against the IDC before assembly, then check for continuity and no adjacent shorts after.
Sometimes I do have to massage (stretch or compress) the ribbon cable into good alignment, beforehand.

7

Test Equipment / Re: Green(Ground) and black (Negative) are shorted on my PSU, is that normal?

« Last post by jjoonathan on Today at 04:20:02 am »

There is a hidden trap for new players in the "social contract" of most DC power supplies: the current limit applies before the output capacitor. This means if you set your power supply to 10V 1mA and connect an LED directly to the output (or connect both outputs to ground), the power supply will not pump more than 1mA into its output capacitor but the output capacitor will happily dump far more than 1mA into the LED until its voltage has fallen to steady state. This kills the LED (or causes a spark) because the short circuit current of the capacitor is large. Intro EE classes often buy fresh LEDs for their first lab class because it is expected that many students will learn the hard way, even if the instructions try to warn. You are not alone in this, it's a universal experience.

I have noticed extra caveats that come with cheap power supplies. A common one is that if you do not turn off their output before cutting power, they dump their intermediate voltage caps directly into the output (in my case, this was 42V for about 20ms). I have also seen a protection function that when engaged does not go to zero but rather outputs -1.2V and -20mA on a supply that was supposed to be positive only. The bigger point is: cheap power supplies do weird things. I have not seen the behavior of periodically shorting the negative terminal to ground, I would typically expect the terminal to be isolated, but I would not be surprised to see such silly behavior from a cheap supply.

As you might expect, more expensive supplies tend to diverge from baseline in the opposite direction. Expensive power supplies from Keysight (or so) will sometimes support "downprogramming" -- intentionally draining their own output capacitor to reduce voltage quickly for waveform generation or to quickly enforce current limits. SMUs also typically don't have the output capacitor caveat. If you set them to 10V 1mA and short the output, the only surge will be the surge required to drain the parasitic capacitance of the wires. The 1mA limit will apply inside a microsecond rather than after many milliseconds. You pay a pretty penny for these features, though, so it is best to learn how to deal with regular power supplies first.

The oscilloscope is probably fine. They are usually constructed with probe ground directly connected to the chassis. You could likely dump enough current into your probe ground to make the wires glow red hot without damaging the actual signal processing hardware in the scope. The melted probe would need to be replaced, of course, but that would be the end of it.

8

General Technical Chat / Re: Whats your Work-Bench/lab look like? Post some pictures of your Lab.

« Last post by BlownUpCapacitor on Today at 04:19:32 am »

Ya know... about a year ago, it looked something like this. Ever since my projects have gotten more complex. My issue is space for stuff. My room is about 8ftx8ft, or about 2.5mx2.5m for those of you who use metric.

9

Security / Putty/FileZilla - Keygen Vuln

« Last post by bingo600 on Today at 04:16:30 am »

Not likely to be  a "bad one" , unless you are commting to git etc. with Putty.
But do update your Putty, FileZilla etc ...



https://www.cvedetails.com/cve/CVE-2024-31497/
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-31497

All NIST P-521 client keys used with PuTTY must be considered compromised, given that the attack can be carried out even after the root cause has been fixed in the source code (assuming that ~60 pre-patch signatures are available to an adversary).

### Mitigations

This vulnerability has been fixed in PuTTY 0.81, FileZilla 3.67.0, WinSCP 6.3.3, and TortoiseGit 2.15.0.1. Users of TortoiseSVN are advised to configure TortoiseSVN to use Plink from the latest PuTTY 0.81 release when accessing a SVN repository via SSH until a patch becomes available.

10

Mechanical & Automation Engineering / Re: somoene finally built a solid state dehumidifier based filament housing

« Last post by NiHaoMike on Today at 04:10:53 am »

Interesting technology, but leaving excessive O2 around in a closed container will likely cause issues with some materials!!

Then put something inside to use up the oxygen without generating moisture? Carbon comes to mind as something that's cheap and readily oxidizes, the tricky part is figuring out how to do that in a well controlled manner, without generating hazardous amounts of CO.

Heater is obviously faster, as was noted in the video, but energy costs are high right now for some countries, so they are avoiding that solution.
I'm sure a 3W heater would not work as well as this device.

How about a simple solar thermal collector?