EEVblog #1137 - Mailbag Monday

Mailbag Monday

SPOILERS:
12:20 iTron VFD Displays
16:06 Oscilloscope Component Tester
In-depth description of the project:
22:23 Random Chinese Mailbags

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[TheBreadboardca]

The charger output is designed to increase as current goes up in an attempt to compensate for typical cable drop so it delivers the right volts at the end of the cable, not at the charger port. I reviewed one of these a few months back and overall it is a nice device but it is basically a dumb charger. no negotiation with the connected device. great for a bench supply for all those Raspberry PI projects and the like.

[hene]

Oh those finger condoms... Lol I wish they wouldn't say that in the packaging... All the fun I could have while ordering them to friends.

[StrongOneX]

The cell phone part from China is the camera "visor" for the Nexus 6P I think. They are notorious for breaking when disassembling the phone for repairs.

[bjornroesbeke]

Smart chargers are trying to sense the capabilities and requirements for the connected devices, devices are trying to sense the capabilities of the charger.
Both fall back to the lowest possible current. Can you see the problem here? Just output the 5, 2V dammit!

It's like graphics cards and monitors. The graphics card won't output a signal if it doesn't detect a monitor first and the monitor won't allow to select an input until a signal is applied first.
The "smarter" devices become, the more it makes me go medieval on them.

[williamsquires]

Hi Dave! Re: the curve tracer. I did something similar - but much simpler - in EE lab in College. I just took a 12 VAC wall-wart, a 1% 1k resistor and the DUT. Wired the 1k resistor in series with one lead of the transformer secondary and a solderless breadboard to mount the DUT. The other lead of the xfmr went to the DUT, and the other end of the resistor to the other lead of the DUT, so all in series. Now hook the X-axis across the DUT and a small 1:1 toroidal transformer across the 1k resistor, with the Y-axis on the other side of said toroidal transformer; this way, the Y-axis is not ground referenced to the circuit. Set the scope for X-Y mode, and hook up the DUT. Set the scale and have fun testing components. I was able to demonstrate the correct “waveforms” for resistors, capacitors, inductors, diodes, and a small zener diode as well.

[leisergeist]

You've heard of Edward Scissor Hands, well here's Dave Condom Hands

[foxpup]

Loved your show. First one I've seen. Will watch more. :-) Watching you talk while swinging the knife around makes me feel sentimental. My mom used to talk in the kitchen while flailing a knife around like that. We kept our distance. Good old mum. How I miss her. :-)

[voltlog]

the pirl charger actually compensates for the voltage drop you would get on a USB charging cable while running at 2A.

[StrongOneX]

It looks like the top part of the USB charger (lid?) has a square cutout of the USB ports so it would take the strain off the sockets when you 🔨 the ports. Also the ruideng USB meter and RD USB load behaves like that when you go over the limit of what the supply can suffer, the screen turns blank but it will still draw an odd amount of power although reduced from what initially set. Got the same thing here on Ruideng um34 and Ruideng t64 together with their ld25 and hd35 USB loads. No fault on the charger so to say. Shame about the lack of quick-charge.

[jagardina]

On the pirlcharger web site, they mention something called Wire Compensation "to compensate for power loss in wires and connectors." That would explain the increase in voltage as the current went up. It's by design.

[MegaSmiley]

The thing at 23:00 is the back glass panel for a Nexus 6P phone

[LucasHartmann]

On the Octopus curve tracer: Connect both grounds to the shared XY terminal, the probes to X and Y, and set the scope to invert one of the channels. No differential probe required. Used to do that to test PV panels.

[alecapristrudel]

What's the point of that "curve tracer" when you need an fgen and differential probes. As it is it's just an opamp and a shunt resistor. At least build the ramp/triangle generator into it....

[DavidGranz]

The Itron 7000 series displays don't do 4 bit mode. It's likely that's why your test didn't work.

[TheDefpom]

Hasn't that charger featured before? I remember that odd LED display, the vac display seems familiar too.

[Arek_R.]

That TI IC says something about cable compensation, that's why you get that voltage raise.
I don't understand why you dislike it.
Very often smartphones will charge at full current only if you feed them at least 5.2V because of the voltage drop.
Yeah 5V is the perfect value but it's not anymore when it reaches charging IC with 4.8V...
Anyway that Pirl chargers seems to be quite a crap, and probably expensive, just because of that display.
You can get 5 port mains PSU from BlitzWolf, 2.4A each, with support for for 5V handshake protocols, for like $20.

[merlingallagher]

Why not just adding a differential to single ended converter into that curve tracer. That's not to difficult to add?

[cyberspearmint]

22:45 Nexus 6P replacement glass for the camera "visor"???

[zachadams]

That's a replacement camera/flashlight glass bit for the Huawei Nexus 6p, which i have. Mine is broken. It broke yesterday. Conspiracy?!

[kazriko]

Those Noritake displays also have a serial port interface and serial protocol, I think RS232 even? It's been 12 years since I last used them.