[Arm-netbook] Oscilloscope or bust?

[David Niklas]

On Sun, 9 Sep 2018 23:25:42 -0400
David Niklas <doark at mail.com> wrote:
> Hi,
> I need help here. I was designing the power supply of my laptop and I
> noticed that some power bucks and step up/down converters (Which both
> seem to do the same thing. Please tell me otherwise.), produced a more
> stable power supply than others. In order to find out if they are truly
> suitable for suppling power to sensitive electronics I've heard that I
> need an oscilloscope.
> I currently own:
> 
> 1. #222634543946
> "DC-DC 10/12/15/20A 150/250/300/400/1200W Step up Step
> down Buck Boost Converter"
> 
> 2. #152710861245
> "2A DC Boost Step-up Adjustable Converter Module 3v-24v to 3.3v 5v 6v
> 9v 12v 24v"
> 
> After learning that some guy with an oscilloscope reviewed these, I'm
> planning to get: #122923215542
> "6 Pack MP1584EN ultra Small DC-DC 3A power Step-Down
> Adjustable Module Buck M2H3 6 Pack MP1584EN ultra Small DC-DC 3A power
> Step-Down Adjustable Module Buck"
> 
> I've seen many oscilloscopes online on crowd funding campaigns. I've
> never been certain of which to get, if any. The real professional ones
> are out of my budget range of about $100. *I'll pay more if I must*,
> but I already did not anticipate the need to actually evaluate what
> should be solid products.
> I probably should find a solid adjustable DC power supply to test these
> with vs. an old laptop power pack or some batteries.
> What I need some of these things to do is to take a dynamically variable
> voltage as input (Li-Ion batteries in series), and produce a constant
> voltage as output. Others I need to just convert to the correct voltage
> from the old laptop power pack.
> 
> Thanks!
> David

Alternatively, does anyone know a good place to ask?

I searched a lot online and found a forum www.electro-tech-online.com
which I signed up to and was rejected. It was a very weird sign up
process. You're supposed to input your name but the form will only take
one character (and allows white space as that one!) You also have to tell
what education level you're at (I choose student), and what your
expertise is, which being a student was none, but they did not have that
choice and the others were things like "PCB layout engineer," so I
selected everything.
After being rejected I wrote to the admin asking the reason and have yet
to get a response after about a week...
In other news, I found a couple of guys on youtube who did a review of
the 300W buck converter I own and it seems to be a good model with a
168mhz switching freq and 218ma voltage variation independent of load, but
I must confess that I have not done any work with computer circuits until
now so they might have stricter requirements than I think.
So, I think I'll add a 3.3uf capacitor onto the leads and call it quits
from there. 3.3uf should be able to reach saturation at 168mhz unless my
calculations of the time constants are incorrect. Feel free to check me
on that, I did use a calculator this time (I learned via pencil and
paper and I still have my notes!)

Still, I think I could use a good place to ask these questions on because
although this list is called "arm netbook" it seems that a lot of
questions I post on the subject go unanswered, but that might just be my
perception :)

Status update: other than the above, I'm still trying to find genuine
Li-Ion batteries (both my stock of Li-Ion and my Ni-Mh batteries are
duds. I did replace the Ni-Mh ones), and I managed to fry a pair of my
tester leads (turns out that the tester is rated for 10A and the leads
for 8A? So I'm building an open source set of leads. :) They "mind
melded" to each other when I decided to test if my 300W buck converter
would work.
Another annoying thing is that it turns out that electrolytic capacitors
are being faked in addition to batteries. I never needed a capacitor
tester before because the ones that were not bulging were marked and the
ones that are bulging are not safe. So I am getting a little TC1
multi-function tester that was reviewed here:
https://lygte-info.dk/review/ComponentTester%20Multifunction%20Tester%20T1%20UK.html
The gentlemen also reviewed a bunch of batteries, but most of them are no
longer available or are very expensive.


Thanks!