Recent Posts

1

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?

2

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)?

3

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.

4

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).

5

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.

6

Beginners / Re: Automatic golf ball dispenser

« Last post by Maclarkson on Today at 09:27:39 pm »

Hay guys, sorry it took so long to respond, I went out to get some parts.

What there is left to right

Battery pack
Something that I don’t know
Relay switch
A timer
A vibration switch
Solenoid
And an arduino uno
Plus plenty of bits

I think I have enough to create something. But as mentioned about I want the vibration switch to trigger the solenoid. I’d like connect this to the T so that when I swing at the ball it triggers a new ball to load.

7

Projects, Designs, and Technical Stuff / Re: How is a motor run capacitor sized?

« Last post by bdunham7 on Today at 09:27:36 pm »

What is the exact size?  Especially diameter and lead spacing.

8

General Technical Chat / Re: Looking for reverse osmosis with less than 25% waste

« Last post by thm_w on Today at 09:27:32 pm »

From what I read, typical system wastes 70-90% of the water. So 25% waste would be incredibly hopeful.
Is it necessary to remove the minerals?

https://www.reddit.com/r/WaterTreatment/comments/iiatn5/zero_waste_reverse_osmosis_system/

9

Projects, Designs, and Technical Stuff / Re: How is a motor run capacitor sized?

« Last post by aroby on Today at 09:25:52 pm »

Why do you want to replace the capacitor?

It looks fine.

A friend of mine also has one of these actuators and his board got eaten away, more than mine, with saltwater dripping on it.  I made a replacement board, but need the cap!

10

Beginners / Re: Convert US standard 115V to International 230V

« Last post by tooki on Today at 09:23:51 pm »

My favourite one was when it took several pages to explain why a capacitor connected to a generator doesn't increase the power consumption, ignoring the tiny extra I²R losses.

I missed that thread at the time. And it was before I learned anything about AC theory anyway, so it would have been lost on me then. But I read it now and the obstinance made some of my brain cells commit seppuku. I find it hilarious that the thread contains a literal crayon drawing that explains it clearly, but still it continued for pages and pages…