Recent Posts

21

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.

22

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.

23

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.

To avoid further bricking you can make a simple script that restores phoenix after several boots.
USB console will probably fail to work if phoenix crashes but give it a try.

Create a file named "S11_restore_phoenix.sh" in the root of the USB drive.
Ensure it uses UNIX new line format!

Code: [Select]

#!/bin/sh

# Read file, increase counter
import /etc/phoenix_count
PHOENIX_COUNT=$(($PHOENIX_COUNT + 1))

if [ $PHOENIX_COUNT -lt 3 ]; then
  echo "PHOENIX_COUNT=$PHOENIX_COUNT" > /etc/phoenix_count
  sync
fi

# Restore after 3 boots
if [ -f /dso/app/phoenix_bak ] && [ $PHOENIX_COUNT -gt 2 ]; then
  pidof phoenix dbus-daemon | xargs kill -9
  cp /dso/app/phoenix_bak /dso/app/phoenix
  chmod +x /dso/app/phoenix
  sync
  reboot -f
fi

Add this to do_other_update:

Code: [Select]

# Make phoenix backup and copy the restore script

if [ ! -f /dso/app/phoenix_bak ]
  cp /dso/app/phoenix /dso/app/phoenix_bak
  cp /mnt/udisk/S11_restore_phoenix.sh /etc/init.d/
  chmod +x /etc/init.d/S11_restore_phoenix.sh
else
  # reset counter, start over
  rm /etc/phoenix_count
fi

# Copy your modded phoenix from usb drive
cp /mnt/udisk/phoenix /dso/app/
chmod +x /dso/app/phoenix

Copy the modded phoenix to the root of the USB drive and run do_other_update with Script launcher.

Working or not, after 3 boots (Wait until the second Hantek logo shows up, then another 5-10 seconds) the original file will be restored.

24

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?

25

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. )

26

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?

27

Beginners / LC filtering for combined Vref/VDD of ADC

« Last post by HwAoRrDk on Today at 09:32:43 pm »

I am looking to use a Microchip MCP3202 ADC, but it does not have a separate Vref, only a combined Vref/VDD pin. I'll be powering it with 3.3V, but the power rail will be unavoidably noisy (around 100mV pk-pk noise), so I think it's a good idea to filter the power supply.

Because I don't want to greatly lower the impedance of the power supply then an RC filter is not suitable, right? So I'm thinking what I need is an LC filter. But still I'm a bit of a noob at all this kind of analog stuff and I don't really know what I'm doing, especially the maths.

I've been tinkering around simulating a low-pass filter that has a cut-off frequency of about 50 kHz with 10 uH inductor and 1uF cap, but it also seems to self-oscillate around that frequency, amplifying the noise greater than the input. If I add 10 ohms series resistance (i.e. turning it into RLC), it's fine. Should I be adding the DCR of the inductor as 'R' to the simulation? Most 10 uH inductors in 0805 package (what I plan to use) seem to have a DCR spec of 1.15 ohms. Or should I not be too concerned about needing to add 10 ohms, as the ADC only consumes about 550 uA worst case (according to datasheet)?

28

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

« Last post by tooki on Today at 09:32:01 pm »

I didnt delete anything.

I know you didn’t, which is why I never said you did. I said that the post you were REPLYING TO was deleted. See your replies #5 and 6 above? There used to be another post between them. That post was from someone else. They deleted it after you replied to it.

The fundamental freq at 800kHz was a problem . Yu cant meet CISR25 with a transmitter running inside the AM broadcast band
never mind the harmonics.

So wouldn’t the harmonics have made EMI emissions even worse?!

The problem for the devices was the lack of harmonics (IE being not square waves, IE without necessary fast risetimes to ensure the transition between 0 and 1 is fast enough to avoid the chip toggling states internally as it passes through the threshold band.),

Sure. But that’s not an EMI issue.

Is there some reason you are reluctant to share any of the requested information, like a block diagram? Super frustrating.

29

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

« Last post by shabaz on Today at 09:31:33 pm »

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).

30

Test Equipment / Re: New Hantek DSO2X1X models?

« Last post by DavidAlfa on Today at 09:31:11 pm »

I uploaded Semenich56 GD5F1GQ5UEYIG dump into DSOFlash folder.