Recent Posts

1

Other Equipment & Products / Re: Filter advice please on home made fume extractor

« Last post by shabaz on Today at 09:55:08 pm »

I used 120mm fans (since I had a load of them) and had to use 4 of them I think, to work through that filter!). A larger filter and different (and larger fan) topology for that sounds very sensible.

Also you're right on the noise (I was hoping to put it under the desk with just the ingress hose exposed, but it's still unnecessary sound that could be solved by better design). Also needed a soft-start (I used extremely crude series resistors shorted out by MOSFET delayed by RC circuit) since the fans have so much demand on start-up. I definitely would scale it up and do things differently if I were to do it again.

2

Test Equipment / Re: New 2ch pocket DSO+SG - Zeeweii DSO2512G

« Last post by Aldo22 on Today at 09:54:32 pm »

What sources do you use for AC and DC calibration?

With what I had at hand.
I took my FY3224s and verified the voltage with the multimeter. This for all voltage ranges, but only at 1kHz.
Here is a photo of it: https://www.eevblog.com/forum/testgear/new-2ch-pocket-dsosg-sigpeak-dso2512g/msg5086450/#msg5086450

Today I might do it with my second scope.
But you shouldn't exaggerate, it's not a high precision device. 

3

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by Martin72 on Today at 09:48:40 pm »

What was the topic again?
Question for a friend...

4

Test Equipment / Re: New Hantek DSO2X1X models?

« Last post by Pin240 on Today at 09:46:10 pm »

I would start by searching "Hz", "KHz", "MHz" strings in the binary and finding where they're being used.

I found them in Phoenix and in some xml files.

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Other Equipment & Products / Re: Filter advice please on home made fume extractor

« Last post by thm_w on Today at 09:43:53 pm »

Do you think this will be OK?

£16.50 for 2.5 kg

Looks good

Some vacuum-cleaner filters are a decent size, I gave it a shot a while back too, I can't say I was entirely happy with it all (it was a bit experimental; it would probably need a rebuild, with more air-tightness around the fans). I didn't complete : ( But I was happy with some aspects of it, it needed better execution. For the ingress end, I used a 3D-printed oval-shaped funnel, connected to a short length of conductive plastic hose (from eBay).

Tooki beat me to it. Your construction looks very good but, the vacuum these filters are from is probably using a 500W+ centrifugal motor. Those 3 axial fans you have most likely aren't powerful enough in comparison. You could 10x the surface area of that HEPA filter and greatly decrease the pressure needed, which might make those fans usable (depends on their static pressure rating, if its from a PC they are probably no good).

Also that mesh carbon filter is near useless. Get some granulated media in a mesh bag if you can.

6

Projects, Designs, and Technical Stuff / Re: digital RGB LED question

« Last post by glenenglish on Today at 09:37:25 pm »

harmonics maybe might have made EMI worse, it depends on their amplitude, which might depend on the cable characteristics, the driver characteristics, the load characteristics...

problem 1-
the lack of sharp edges mean the link is unreliable (those chips need square waves). long periods in the transition region  leads to (even poorer)  RF immunity
problem 2-
signals in the broadcast band on unshielded cables are radiators and likely cannot meet CISPR25 etc emission requirements, and are likely to cause harmful interference to you and your neighbour's listening of the radio.

7

Test Equipment / Re: New Hantek DSO2X1X models?

« Last post by DavidAlfa on Today at 09:36:29 pm »

I can't, I don't know.
Try disassemblying phoenix in Ghidra, that's how I did everything, but it takes ages to find anything out and even more to modify, it's anything but easy.
Read the hacking thread, specially this message.

I would start by searching "Hz", "KHz", "MHz" strings in the binary and finding where they're being used.

8

Test Equipment / Re: New Hantek DSO2X1X models?

« Last post by Pin240 on Today at 09:35:15 pm »

I uploaded Semenich56 GD5F1GQ5UEYIG dump into DSOFlash folder.

Thank you. Already found and restored.

If you have time, can you describe how to modify the graphical interface?

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Other Equipment & Products / Re: Filter advice please on home made fume extractor

« Last post by tooki on Today at 09:35:12 pm »

That’s tiny compared to what you want for a filter that shouldn’t make tons of noise (by needing a vacuum cleaner’s static pressure). And it has very shallow pleats.

Look at this instruction sheet for an idea of the scale one wants for a large-surface (=low pressure, quiet) filter system: https://www.southernfilters.co.uk/theme-content/uploads/2017/07/unpack-hepa-filter-1.pdf

(No, you don’t need one quite that big. But closer to that than to PC fan size. )

10

Test Equipment / Re: New 2ch pocket DSO+SG - Zeeweii DSO2512G

« Last post by Sham73 on Today at 09:33:38 pm »

**Open user calibration function.
How to perform AC Gain calibration:
1. The oscilloscope measures the 2.5V 1Khz sin waveform. Observe the "PKPK" measurement item.
2. Open Menu-> Meas, then press the CH1CH2 button, and then long press the [mV] key to enter the AC Gain calibration mode.
3. The UP DOWN button is used to increase/decrease the CH1 Gain until the "PKPK" voltage is equal to or close to the voltage of the signal generator.
4. The LEFT RIGHT button is used to increase/decrease the CH2 Gain until the "PKPK" voltage is equal to or close to the voltage of the signal generator.
5. Press the OK button to exit and complete the calibration.

How to perform DC offset calibration:
1. The oscilloscope measures the DC power supply. Observe the "Mean" measurement item.
2. Open Menu-> Meas, then press the CH1CH2 button, and then long press the [V] key to enter the DC offset calibration mode.
3. The UP / DOWN button is used to increase/decrease the CH1 dc offset until the "Mean" voltage is equal to or close to the voltage of the multimeter.
4. The LEFT / RIGHT button is used to increase/decrease the CH2 dc offset until the "Mean" voltage is equal to or close to the voltage of the multimeter.
5. Press the OK button to exit and complete the calibration.
Different vertical sensitivities use different calibration parameters, so they need to be calibrated separately.


**add [ZOOM]
Long press the "s" key to turn on/off Zoom mode.
(Zoom is not supported when roll mode or cursor is on\
It is recommended to exit Zoom mode before shutting down to avoid measure item are cleared)

What sources do you use for AC and DC calibration?