Recent Posts

1

Buy/Sell/Wanted / Re: SALE (AU/NZ): Multicomp Pro MP710086 (Owon P4305 rebadge) at element14

« Last post by plurn on Today at 02:02:52 am »

Not that it matters anymore since these cheap Multicomp Pro MP710086 power supplies have sold out, but the two I just received both have a really annoying and loud transformer buzz that the first one I got does not have (or it is quiet enough not to be noticeable). The new ones are at a slightly different tone to each other. They buzz all the time the main power is on even if the output is off. The buzz is just as loud as the fan is when you short the output.

It is an outrage - for AU$61.47 inc gst I expect perfection - kidding

Other than that, these buzzing ones did not have big holes in the boxes and they had Australian power cords with the other power cords missing. The buzzing ones are from December 2022 batch and the quiet one is from May 2022 I think. It will be pretty rare that I use these two so not a huge issue.

2

Other Equipment & Products / Microscope Parts Help

« Last post by arduic on Today at 02:01:27 am »

I recently inherited this beautiful amscope microscope but I've run into an issue while trying to get replacement parts for what is missing.

I can not find a single label on this thing telling me what amscope product it actually is. Does anyone know of a way to figure this out? How am I supposed to know if this is an SM or a ZM series microscope?

Additionally if people can help me determine what I am missing I would be so appreciative. I can tell I am missing 1 eye piece. Since I want to do SMD PCB work I definitely want to get a barlow lense. However I can not tell if there should be something after the black piece at the bottom of the scope.

The zoom on my microscope also seems completely out of wack. This could be from lack of necessary equipment but when a PCB is in focus under the scope the work area is maybe 5% of my view the rest is all black. Do I just not have a scope made for PCB work or is my lack of some equipment causing the issue?

3

Microcontrollers / Re: [Video] Embedded TCP/IP stack explained: step-by-step code walk-through

« Last post by PDP-1 on Today at 02:01:10 am »

That's really cool, thanks for sharing!

I wrote my own bare metal driver for an STM32F429 last year, it was a much less ambitious project as it's only ever intended to run on that chip with IP4 UDP and very simple sockets only, and no gateway/DHCP implementation as it is never intended to talk to the outside world. Just enough ARP/ICMP is there to ping the thing.

One big difference I saw was that you were doing memcpy in the IRQ, while I used pointer math to pop say a received packet off of the Rx DMA chain and move it to a queue where it would later be picked up by the main thread and processed up the stack. Then I'd grab another Rx buffer descriptor out of a pool of unused ones to replace the one I just took and keep the same number of unused Rx descriptors on the Rx DMA queue. I figured that was a bit less work for the CPU than copying buffers and got out of the interrupt handler quicker.

I still need to watch through the TCP part as that's something I'd like to add to my system some day. It was neat to see how someone else approached the STM32 Eth/MAC implementation. You really can make a small, performant Ethernet implementation on those chips but it's amazing how obfuscated the poorly written datasheet makes doing it for the first time.

4

Test Equipment / Re: Fluke 8060A Somewhat Functional

« Last post by blue_lateral on Today at 02:00:54 am »

DONT put deoxit in the switches as someone suggested earlier. That is a mistake. I did that once many years ago. It's apparently too conductive for the high-Z circuitry. It is very hard to get rid of. Several washings with isopropyl did eventually make the meter functional again.

The "old fluke multimeters" thread referenced in an earlier post is the one you want.

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Microcontrollers / Re: STM8S and STM8L microcontrollers were NRND, now in active production again

« Last post by prosper on Today at 02:00:04 am »

the '10 year' guarantee still says it expires in the 032, though. So - typo, or still effectively NRND?

Regardless, they do appear to be in mass production and available at low price...

6

Microcontrollers / Re: It Came from Mainland China: Bootleg MCS-251 "32-Bit 8051"

« Last post by Dass347 on Today at 01:56:33 am »

this is a crap and should be avoided to use.

It sure is, but it's interesting crap.

Here's a copy of the STC32G datasheet I ran through Google Translate.
There's some graphical issues with it, so it helps to look at it alongside the original Chinese datasheet.
While STC has published newer versions since, I've been too lazy to dice up a copy of the Chinese datasheet and run it through Google Translate a second time. I don't think the revisions have been major, but I'm not 100% sure.

The STC32G April 1st datasheet in Chinese:
https://drive.proton.me/urls/2Q7AR1TEN8#NRsdsx7shtIq

The Google Translate English version of it:
https://drive.proton.me/urls/FJP87GB9ZR#8WTHykn75WHk

I also want to note that I tried DeepL as well, but it had a nasty habit of randomly inserting extra blank pages, breaking the page number equivalency with the Chinese datasheet.

7

Projects, Designs, and Technical Stuff / Re: Disadvantages of Using Push-Pull in Pure Sine Wave Inverter?

« Last post by Xena E on Today at 01:56:08 am »

Curious minds want to know how it is possible to drive a iron cored line frequency transformer with a PWM 15,625Hz square wave directly into the windings, and it does it with high efficiency and producing an averaged pure sine wave at nominal line frequency over its full range of loads, as an output.

Perhaps curious minds can set up an experiment and demonstrate it themselves.

Reporting back with real calculations and waveforms would provide valuable grounding to the discussion in this thread.

Tim

If by that Tim, you mean the original poster providing circuit diagrams and details of his build that he was asking for 'help' with, which I have only a very vague impression of, and that impression of what was built would not work to the claimed efficiency then yes, he should.

No one can form any opinion about this "project" without the details of what was done.

Extraordinary claims require extraordinary proof, there's been no proof and the story keeps changing.

I'll wait for Kerim F to post those details, and prepare to have my socks blown off. In the mean time stick to working with the idea that DC link bridge output inverters, are as good as things can get.

Regards.
X

8

General Technical Chat / Simple technical illustration software/tools?

« Last post by forrestc on Today at 01:50:38 am »

I'm struggling to find the right tool - I'm guessing it probably doesn't exist all in one tool but it doesn't hurt to ask.

I need to draw some semi-technical drawings on a fairly regular basis. These are the types of drawings you'd see in a user manual or online as part of a guide on how to do something. Quite often, they're wiring diagrams or other diagrams showing how to do something slightly mechanical, etc.   Most are for teaching and/or assembly instruction type purposes.

I've tried a lot of tools, and had started describing what I liked about each, but instead maybe I should just put what I'd like into a list, so here goes:

• Ability to paste clipart or other images
• Text tool optimized for adding text to images.  For example, being able to place a contrasting 'outline' in order to make the text stand out from the image
• Various easy to use 'callout' tools.  I.E. arrows and balloons.    I'm not talking about clipart of these elements - actually being able to draw a callout of a few styles is needed
• Line tool which is optimized for connecting two points on two objects.  i.e. I want to draw a line between two connector pins and have it look like a wire instead of a square line with poorly-connected corners.   It's amazing how many tools let you draw lines, but don't make it easy to "connect" two objects with a line, or worse, think a bezier curve is the solution for anything curvy.
• Useful coloring options for lines - for example, I need to be able to represent wires that are 'white with green stripes'.  I don't care if it's alternating white/green dashes with a black outline, or if they're angled or something else, but I do need to be able to represent them
• Visually good looking results from above.   Don't want horrible text rendering, want my callouts to be visually nice as well.  This means that the software probably is a bit 'graphically opinionated'.  I can live with someone else's design choices here as long as the result is usable

I'm sure I've left some things off, but I think this gives at least the gist of what I'm looking for - a simple way to markup or draw images which are of the type that you need to draw to explain some technical concept to someone else in electricity/electronics, but without resorting to full-blown CAD software or doing a schematic (that a lot of people can't read anyways).

Some things I've tried:  Snagit editor hits most of the points here, but their line tool is atrocious.   Smartdraw has a good line tool (except alternating color options), but is pretty dismal everywhere else.   Visio is just a PITA licensing wise and it isn't really what I'm looking for.  I've tried various CAD packages, but that's CAD and either you spend a lot of time doing 3D or you end up with a mechanical drawing which isn't the goal here.  Photoshop and similar tools are too feature rich (but they're great if you want to do it all by hand).  I could go on, but I won't.

So, anyone have a quick drawing tool they like which allows them to produce good looking drawings without a lot of work?

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Buy/Sell/Wanted / Re: SALE (AU/NZ): Multicomp Pro MP710086 (Owon P4305 rebadge) at element14

« Last post by chubbymonk on Today at 01:47:31 am »

Several reports in another forum of people getting orders cancelled after they've been OKed because the AU warehouse is now out of stock and the order would otherwise be fulfilled from the UK.  Also be very, very careful about what you get charged on checkout, some people have reported being charged the non-sale amount because the order was switched to the UK.

Interestingly seems like my order might have slipped through... I had ordered one of the cheap Tenma supplies (rebranded Korad) on sale and it ended up being shipped from the UK with the sale pricing being charged. Received it a couple days ago and the invoice does indicate the sale order code. 

10

Test Equipment / Re: dual knobs for time/div on leader 8060 oscilloscope

« Last post by bdunham7 on Today at 01:31:02 am »

A and B are triggers, also called A sweep and B sweep.  The scope is dual-timebase, which means that it can use two different horizontal sweep rates for the two different trigger events.  This is a "zoom" function that allows you to magnify (horizontally) one particular part of the waveform.  This is not the same as CH1 and CH2, you cannot have different timebases for the channels.  The B-sweep cannot be slower than the A-sweep, so if you turn the B-sweep timebase knob counterclockwise, it should eventually catch the A-sweep knob and turn that as well.  If it hasn't done that, then adjusting the B-sweep timebases should have no effect on your A-sweep appearance.  The picture you posted shows the scope configured to only show the A-sweep but I can't read the B-sweep timebase setting so I don't know if this is an issue or not.