Recent Posts

1

Beginners / Re: Data logger - separate power supply with isolation?

« Last post by Sikanda on Today at 07:14:12 am »

@shabaz
Also, unless you've already ruled it out, you could consider a microcontroller, e.g. Pi Pico instead of Pi, unless you really need network or other Linux capabilities. Pi Pico can log to Flash or to micro SD for instance. Anyway, it's just a suggestion in case it sounds appealing.

Raspberry Pi seems a bit over the top. But it is mainly for the ease of programming. I can plug in a USB stick, download the data and have it running. With a microcontroller, I would have to do a lot more programming.

@PGPG
I understand these 4 devices are powered from data logger and have no other connection to building earthing system. True? If not true then you should consider isolation between them.

Yes, all devices are powered by the datalogger.

@PGPG
I would use microcontroller having 4 UARTs and one SPI and one more UART or SPI to communicate with Raspberry. if you want to isolate Raspberry from your own supply than you will have to isolate only one link.

That's a nice idea. I will think about it.

@thm_w
Having one isolator for I2C means all the RS485 connections are then common. I guess you are planning to use something like SC18IM704PWJ which is not cheap.

Yes, I was thinking about the SC18IM704PWJ, but maybe I will go for the one microcontroller suggestion from PGPG.
The advantage of the SC18IM704PWJ would be that I could use a Linux driver for the chip and easily access each RS485 port.

@thm_w
Can you have all the RS485 devices on one bus? Or you think that is too risky.

I rather have a direct link to each device. If for some reason there is a problem with the wiring the whole measurement gets disturbed.

2

Beginners / Re: BM786 continuity beep not latched

« Last post by woox2k on Today at 07:13:59 am »

There are only two dealers, Welectron who order direct from Brymen, and Simon from Sparky Labs who orders from me.
I handle all other global shipments from my lab here.

Whoops, sorry. Apparently you are a hell of a lot more involved in handling those meters than it makes sense! Nice! That doesn't help people around the EU though (or the people who already have purchased the meter)... Meters sold by Welectron have not been upside down at your place Ordering one directly from you would probably cost an arm and a leg, plus a large amount of money. Same with sending it to you in order to get it flashed and shipped back...

3

Test Equipment / Re: Desktop DSO for hardware and firmware development of MCU systems

« Last post by tautech on Today at 07:11:23 am »

After the scope has capture multiple copies of the trigger event plus one screen width of data around trigger point, I can SEARCH the captured data using different 'trigger condition' to find some abnormal events, right?  For example, pulse abnormally higher voltage;  some has RUNT

Even better: the always active history stores the trigger events for you without the need for you to do anything for it. Up to 80000 trigger events (depending on timabase and memory depth) can be stored in the history and inspected to your hearts content afterwards. All the tools are available and a couple advanced triggers are supported for event search, which works across the history if so desired. Compared to Sequence mode, history is just not as fast and there is no guaranteed max. dead time (down to 2 µs!), which is still sufficient in many use cases.

Many thanks for vast number of tests as in https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293741/#msg5293741

Part one report shows the scope can capture pulse of two to four ns (presumably depends on 1,2 or 4 ch, at 2, 1 and 0.5MSa/s) and SPI decode at tens of time higher than my 10MHz task-on-hand.

Is the software 'practically' no bug for normal use?  Any reason not to buy this (apart from 2000 series has the new serial test mode that measures dozen SPI signal parameters automatically, bigger screen and build-in LA)?

Well we have hung our hat on SDS800X HD models as our low cost but advanced solution as its capabilities well exceed all previous Siglent models at this price point.
Only when you need a 10" display other pricier models get suggested however SDS800X HD is just half your initial budget and I know you will be very impressed with its capability as I have 100% confidence it will meet your needs.

4

Beginners / Re: BM786 continuity beep not latched

« Last post by EEVblog on Today at 07:07:49 am »

At least with Brymen meters Dave doesn't handle every single meter that is sold globally! They come directly shipped from Brymen to resellers around the globe.

There are only two dealers, Welectron who order direct from Brymen, and Simon from Sparky Labs who orders from me.
I handle all other global shipments from my lab here.

5

Beginners / Re: BM786 continuity beep not latched

« Last post by EEVblog on Today at 07:06:10 am »

I personally don't like the scratchy sound either.  One solution: Dave can offer firmware version flash options in his store at an extra charge.

Possible, but postage is a killer.

I mean as part of the initial purchase.  Take it out of the box, flash it, then ship it.

If someone wants to order a special unit then I can flash in 78609 firmware.

6

Beginners / Re: BM786 continuity beep not latched

« Last post by woox2k on Today at 07:05:51 am »

I mean as part of the initial purchase.  Take it out of the box, flash it, then ship it.

At least with Brymen meters Dave doesn't handle every single meter that is sold globally! They come directly shipped from Brymen to resellers around the globe. One option would be to give resellers the option to reflash firmwares but that will not happen (most would not bother anyway) Brymen itself cannot do that because it would be nightmare to keep track of all that stock of different firmware versions. Best solution would be to release firmware files so that users could flash it themselves but sadly that will not be a thing either.

7

Beginners / How to read HRM-10 Internal Resistance Tester

« Last post by bobcat2000 on Today at 07:03:07 am »

I bought a HRM-10 Internal Resistance Tester.  Sadly, I don't know how to read it.  As least I know I need to open the clamps so they are not touching each others before I can get the readings.

If there is not much trouble, would you guys teach me how to read the numbers please?

How do I know if the battery is good or bad from reading those 2 numbers?
Do I fully charge the battery first and then get the readings from the HRM-10?
Run the battery down and get another readings and compare the numbers before I can tell if the battery is good or bad?

Many Thanks!!!

https://www.fnirsi.com/products/hrm-10

8

Projects, Designs, and Technical Stuff / Re: CC/CV Benchtop Power Supply Topology Question

« Last post by ledtester on Today at 07:03:05 am »

The original design started by considering using two linear regulators in series - one for CC and the other for CV - and progressed from there:

EEVblog #221 - Lab Power Supply Design - Part 1
https://youtu.be/CIGjActDeoM

I've seen a similar approach taken with this design:

Build a Small Dual Rail Linear Bench Power Supply. -- TheStuffMade
https://youtu.be/jBtNH1EbU8M

9

Manufacturing & Assembly / Re: Choosing a Desktop Pick and Place Machine

« Last post by 4Project on Today at 07:02:02 am »

I have a Kayo 6 head machine, so nozzle swapping is not such an issue for me. That being said, my machine does not support nozzle swapping and I have to set up my jobs with this in mind.
One idea for nozzle swapping:
You could sacrifice a feeder slot (or 1x1 tray) and setup a fake part. When you need to swap nozzles, have it try to pick up the fake part. The machine will error at the feeder (or tray position). You change the nozzle, then skip over the fake part. Proceed with your different nozzle.
Some caveats:
- You loose a feeder slot or tray position.
- You have to setup your jobs with the fake part where you want to do the nozzle swaps = extra work and consideration.
- I can't seem to skip errored parts on the Kayo without closing the project and restarting after the errored part. So this idea wont work easily for me. You would have to ask them if it would work for you.

That's exactly what I had in mind, but both sales reps are saying that I have to stop the machine manually to do so.
And that's so stupid that I can't accept that's the only option.
I'm paying to get a more reliable machine, so I won't have to babysit it, and they want me to press the pause button in the exact millisecond before the big chip is mounted...

QiHe is saying that the machine will not stop from the beginning.
YX first said the machine will stop on error, after that said it will not and I can see what happened in the log.
The log makes sense, so the production might continue and fix the problems later, but that doesn't leave me the option to do the nozzle change.

On the other hand, I'm not sure if a nozzle change in the middle of the job is a good idea, since it might move the head out of calibration.
If the machine is not aware of it and doesn't recalibrate it's position relative to fiducials, than it might screw the rest of the job.

2 separate jobs with nozzle change in the middle is probably the way to go, so the machine can recalibrate on the fiducials on each job start.

10

RF, Microwave, Ham Radio / Re: 434 MHz - Educate me on Dipole Shortening

« Last post by A.Z. on Today at 06:59:31 am »

A note, the rectangular loop I proposed presents a 50 Ohm impedance at the feedpoint, the circular one you're considering won't, so in this latter case you will need some impedance matching