Recent Posts

1

Manufacturing & Assembly / Re: JLCPCB Global Sourcing -- experiences and cost?

« Last post by daisizhou on Today at 12:43:33 pm »

Sometimes cheap items are not necessarily fake,Because it may be surplus goods。
In the end, you need to keep your eyes open and make a final choice through sharp thinking.

If you only focus on price, you will be easily deceived

2

Projects, Designs, and Technical Stuff / Designing a H-Bridge with only N MOSFETS

« Last post by remopong on Today at 12:42:03 pm »

Hi,

So I was looking for designing

3

Repair / Re: Question about voltage in U.S. house built in 1890

« Last post by SeanB on Today at 12:40:08 pm »

PE getting to half line voltage is almost certainly a ground wiring fault (or that particular socket is not grounded at all), and some appliances connected to the same socket (or same network with faulted ground) are backfeeding the PE.

I'm almost certain with that since the other likely explanation, your utility failed to ground their transformer properly, is fairly unlikely (it *do* happen however, and deliberately done in IT system which isn't usually used for residential).

Hard to do in the USA, as the pole pigs ( house supply transformers) almost always have the neutral connection not isolated from the case, and a ground wire for both the incoming and outgoing supplies, along with ground bonds at each service point. Thus even if the transformer has lost ground, it will be completed via all the other houses, which can make for some hot ground cables on them, and a large neutral earth drop.

Here the house got upgraded to 3 wire outlets but was not rewired, and the only solution is to keep the meter, and replace all the rest with new. If it is rented the landlord is responsible to provide a safe electrical supply, and if it is owned by OP then the seller was responsible to have the house upgraded to comply to the minimum modern scec before transfer.

4

General Technical Chat / Re: Non-contact approach for measuring AC VAC/I and PF

« Last post by NiHaoMike on Today at 12:39:06 pm »

I think you wouldn't want to use an Arduino-powered car. 

Look into what actually goes on in the car modding scene and you'll see lots of sketchy stuff. All so that they can get up to the speed limit a fraction of a second faster and then waste a lot more time than that on more frequent stops at the gas station.

Professionals can afford to create industrial test installations and mock-up products.
Professionals already have knowledge, experience and a sufficient set of tools in the trunk. 

Arduino is for children's study, for learning about the environment when it is necessary to practically try.
Moreover, this is a bad toy, it corrupts, does not form a stable base. She breeds amateurs.

If you are not aware of other means, I can suggest looking at https://www.mikroe.com.

That doesn't solve the problem that much fewer engineers would be familiar with the platform. Guess why most office PCs run Windows even though Ubuntu would be far superior for most uses.

Have you ever imported a MPLABX project and found that you have to make changes for it to compile on the newer toolchain? It's not just Arduino that sometimes introduces breaking changes.

First, scientists use python for mathematical calculations (a stupid tool that basically does not have numbers and variables as such), and then they ask for a lot of money for super computers because they lack performance. 

For the most part, something like 5% of the code tends to run for 95% of the time. So accelerate that with Numba and Numpy or port just that part to C++. The rest of the code remains in plain Python where maintainability is most important. It's worth mentioning that most test scripts are I/O bound and so optimizations are more of carefully planning I/O operations (e.g. start the reading of all measurements in parallel) rather than making the code itself run faster.

5

Beginners / Re: Panasonic polymer capacitor vs other lower brands

« Last post by S. Petrukhin on Today at 12:38:06 pm »

In today's world, the ability to sell is often more important than the quality and purity of the brand.
But look at this: https://www.lcsc.com/product-detail/Solid-Capacitors_Rubycon-25PJV270MVB8X10-5_C2940683.html

6

General Technical Chat / Re: US 50% China Semiconductor Tariff

« Last post by coppice on Today at 12:35:48 pm »

Here in the UK "country of origin is defined as the last country that major work was performed on, so if a kit was produced in the UK that contained a chinese semiconductor, then the country of origin of that kit is the UK.

Country of origin is now pretty much a global term. Without some common standards for these terms each component would need to be produced specifically for it end user country. However, it leads to things like the Philippines and Malaysia appearing to be among the world's biggest semiconductor makers from their markings, because there are major packaging plants there. So, it ends up obscuring more than illuminating.

7

Projects, Designs, and Technical Stuff / Re: High speed ADC multiplexing.

« Last post by max_torque on Today at 12:31:52 pm »

i agree with the last ^^ poster tbh.  AT 200MSPS you'll be wanting a decent analogue front end / signal path, so doing the mplex'ing in the digital domain sounds like the way to go. As you are not requiring fast change to the mutiplex addressing then your multiplexers can be  switched and left, the high speed digital data sent/recieved, and you can then swap to a new m/plexer setting etc

Switching digital logic is also really cheap, so a basic digital buffer with an enable pin can be used to select the digital bus to the correct ADC with very minimal cost

8

Test Equipment / Re: Fun With Low Leakage/Bias Current: Femtompere, Electrometer, Keithley 617

« Last post by ZhuraYuk on Today at 12:31:50 pm »

That is common with sensitive high impedance circuits.  Vibrating wires cause movement of charge.  Mechanically securing the parts and wires helps.

I would tap around with an insulated poker or something to see if any areas are more sensitive than others.

I have 6 electrometers of different vendors including second K617 and non of them is doing that. There is some drift when you shake the device but just a little.
The one I have issues with, goes to higher range even from lightly knocking on the housing.

Anyway, I was able to remove old reed switches from the relays. Some are easily sliding out, some require desoldering the relay and poling the switch with tweezers.
Replaced only first 4 relays and now input current goes to 5fA in 5-10 seconds after switching to amps. Easily can be compensated to zero current.
The original look of the board was  preserved.

9

Beginners / Re: Panasonic polymer capacitor vs other lower brands

« Last post by wraper on Today at 12:29:41 pm »

Take the Panasonic, they at least offer a decent guarantee they will last the required lifetime, and will handle the current with little degradation. The others the Aishi only offers 2/3 the rated lifetime, and the Jianghai looks like a regular electrolytic with a purple top on it.

APC uses nearly 100% Jinghai even in very expensive UPS for a long time. Wouldn't call their electrolytics particularly good though. IMHO does not matter which you use unless it's some extremely high reliability or extremely high stress stuff. Chance of either of them failing is extremely low.

10

Repair / Re: Rohde & SchwarzSMS/SMS2 Microprocessor Board, where is the code/firmware stored?

« Last post by RichardM on Today at 12:28:30 pm »

OK, so after trying another method to dump the 8049 mask rom from https://www.eevblog.com/forum/microcontrollers/mcs-48-disassemble-8049-dump/msg3121778/#msg3121778

I managed to get a consistent rom dump. I have no idea if it is valid code. I used DASMx to disassemble and get the code attached.

Programming this into an 8749, trying this with a 7111 board in a working SMS and........ no change. Just mixed characters on the display. So, maybe there is nothing wrong with the 8049 after all? Or, the code attached is rubbish ? Anyone willing to look at the assembly attached and make an educated post that would be much appreciated

Cheers

Richard