Get your account ready because here comes a new InTheMail and there is a good chance of finding something to order in this video. Don’t forget to use the links below to find the items shown in the video.
Welcome to a new voltlog, today we’re going to test a range of pocket multimeters by applying transient voltages to their inputs and we’re also going to talk a bit about CAT ratings and what they mean.
CAT ratings is something we often see marked on measurement tools and they refer to the measurement category, a method of classification published by IEC (the International Electrotechnical Commission). Different types of circuits will require a different measurement category based on the total energy available in that circuit. For example:
CAT I: is for measurements performed on secondary circuits not directly connected to mains.
CAT II: is for measurements performed on local electrical distribution, such as that provided by a standard wall outlet 110VAC in the US or 240VAC in the EU.
CAT III: is for measurements performed on hard wired building installation, for example distribution boards, circuit-breakers, bus-bars, junction boxes and industrial equipment.
CAT IV: is for measurements performed on the source of the low voltage installation, like the power input to your home, your electricity meter or the primary overcurrent protection device.
As you can see a higher CAT number refers to a circuit with higher available power and higher potential energy transients. Within each of these categories we have voltage ratings and a higher voltage rating means the ability to withstand a higher transient.
Welectron.com which is an authorized Brymen distributor, loaned me the BM887 Insulation Multimeter to perform some testing on the pocket meters. I will be using this meter to apply 1KV to the pocket meters and see how they survive. The BM887 is made for measuring insulation resistance in industrial machines, certainly not for testing multimeter input protection but we can think of it as an abnormal voltage spike that might come rushing through a circuit you are measuring.
In this video I’m gonna show you 3 methods to solder SMD parts but before we get to the actual methods I think it’s best to talk about the type of solder to be used. And there are two main types of solder that you can use, that is leaded or lead free solder. If you are doing prototype work it’s best to stick with leaded solder or solder paste because it’s easier to get right, it has a lower melting temperature. If you are doing production work, you plan to sell those boards, than you might be forced to use lead free solder to be compliant with the regulation.
Welcome to a new voltlog, this is a follow-up on voltlog #148 the pocket multimeter shootout. In that video I reviewed 4 different cheap pocket multimeters. The general idea was that while some had advantages over others they were all missing important protection features on the input, making them safe to use only with low voltage, low energy circuits.
The guys from Welectron saw that video, they contacted me and said they have something better and they sent me the Brymen BM22S and BM27S for a review.
Welectron is offering a 5 EUR discount code (voltlog5) valid until 31st of May 2018. This will pretty much offer you free shipping for one of these meters which coupled with the 3 year warranty and their nice customer service, makes it a very nice deal if you are in the market for a good pocket multimeter.
In this video we’re taking a look at the new Raspberry CryptoPI, a single board computer designed specifically for mining Ethereum. It features 8GB of GDDR6 and a new Nvidia VOLTA GPU. Release date Q3 2018 at a cost of around $400 USD. Let’s hope there will be some units left for us because I am expecting whales to buy these in thousands qty.
Here is a link to the current Raspberry PI: Amazon, Banggood.
If you would like to support the channel you can donate here.
A while ago I showed this power supply kit, which I ordered from ebay. It was being advertised as an LM317 0-15V 0-5A adjustable power supply kit and it looked promising. Upon receiving the kit and taking a closer look theres 2 thing to mention, one the power supply is not based on the LM317 but on the TL431, they used TL431s instead of op-amps in this power supply design and two there isn’t much documentation about this power supply.
The components used are low quality but that is to be expected from these cheap kits coming from china so no surprises there. If you would like to use some better quality parts I would suggest replacing the electrolytic’s and the TL431s with ones sourced from known sources. Also a nice upgrade would be to use some 10 turn pots instead of the supplied ones to get some finer adjustment. But I just used the originally supplied parts to see what kind of results we get with those.
Here is a screenshot with the signal measured right on the bulk filtering capacitor (4700uF). Looks like this might be the cause of the 100Hz oscillation we we’re seeing on the output.
Here is a screenshot with the current overshoot. The power supply was set for CC 50mA and I suddenly shorted the output through a 1ohm resistor. The scope probe was placed across the resistor leads on the low side ( 1mV = 1mA ). As we can see we have a huge spike of current that could potentially fry an LED connected on this power supply. However the spike lasts less than 1mS which is good and I have observed similar behavior on my HP E3611A analog bench power supply.
Here is also a screenshot with the power supply regulating the current at 50mA in CC mode. This doesn’t look right at all.
In this video I’m gonna show you how I build my own Trezor hardware wallet. If you would like to support the voltlog channel checkout the donations page where you will find my paypal address or different crypto wallet addresses.
If you encounter this error while trying to compile trezor firmware:
Traceback (most recent call last):
File "nem_mosaics.py", line 6, in <module>
from google.protobuf import json_format
ImportError: cannot import name json_format
Makefile:121: recipe for target 'nem_mosaics.h' failed
make: *** [nem_mosaics.h] Error 1
It can be fixed by installing googleapis-common-protos package like this:
sudo pip install googleapis-common-protos
This fix was posted in the comments section by a viewer, I verified and it works.
