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RafaelLeeImg
@RafaelLeeImg
By the way, where's the repository of pslab desktop qt?
Padmal
@CloudyPadmal
Hello @RafaelLeeImg , what's the problem you're having?
everthu
@everthu
Hi, I'am new to PSLab and I like the board, but I have some questions regarding the different hardware revisions.
When will the v6 hardware commercially available? and if so, wil the v5 hardware still be commercially available? I'am in the phase of designing a new testsystem and I have to decide which board to use.
Regards, Evert Huijben, Remoticom
CyReVolt
@CyReVolt:matrix.org
[m]
Here's a tweet to action regarding the PSLab desktop app advancement: https://twitter.com/OrangeCMS/status/1488247815516078082?t=swlhlWXcbEVMewhHtmQktw&s=19
I just ran the app on the new laptop running Pop!_OS (System76' Ubuntu fork), working just fine. :-)
CyReVolt
@CyReVolt:matrix.org
[m]
Gamozo did an oscilloscope hack session, quite interesting:
https://twitter.com/gamozolabs/status/1489256493182377984?t=as59fzn_ZQ8-rJDiOLLP2A&s=19
Hong Phuc Dang
@hpdang
We are at fosdem at this weekend here https://chat.fosdem.org/#/room/#fossasia-stand:fosdem.org
Hong Phuc Dang
@hpdang
We are running our regular Pslab meeting at 17:00 CET as usual directly at our fosdem stand :)
@CloudyPadmal @RafaelLeeImg @mariobehling @bessman @nielek2 @orangecms
Daniel aka CyReVolt
@CyReVolt:matrix.org
[m]
What iiif...
You could use the PSLab app in your web browser, without installing it?
Let's say you go to app.pslab.io and then control it via Bluetooth
we'd just need to simplify adding a Bluetooth radio and wire things up :-)
Mario Behling
@mariobehling
This message was deleted
1 reply
Padmal
@CloudyPadmal
@CyReVolt:matrix.org we can also look at the possibility of using WebUSB https://wicg.github.io/webusb/ for connection..
1 reply
I've shared the idea over at #sigrok:libera.chat :-)
RafaelLeeImg
@RafaelLeeImg
After some modification, the oscilloscope works.
I'm reading the python3.9/site-packages/pslab-2.4.0-py3.9.egg/pslab/instrument/oscilloscope.py and power_supply.py
I'm wondering why the abstraction of the two instruments is totally different, why the oscilloscope command is mainly decoded on the PIC24, but power source code sends commands to control I2C bus directly?
Since I'm using two 2-channel DACs on SPI bus, shall I change the abstraction level of the code?
The best practice of abstraction is not overlay between different layers. For example: layer 1, PSLab, layer 2, instrument(oscilloscope), layer 3, (hardware devices MCP4728, ADC, etc).
RafaelLeeImg
@RafaelLeeImg
The newest PSLab desktop version cannot set oscilloscope gain for both V6 and V5, I've changed the voltage range already. Is it not implemented? I've seen python code to change gain, but I cannot verify whether the PSLAB electron app called the function.
RafaelLeeImg
@RafaelLeeImg
I found that the pslab-python is updated, oscilloscope SPI control is added. I'll try with the new one.
Daniel aka CyReVolt
@CyReVolt:matrix.org
[m]
talk for FOSSASIA Summit submitted ✅🥳
Daniel aka CyReVolt
@CyReVolt:matrix.org
[m]
@RafaelLeeImg: see here https://github.com/fossasia/pslab-desktop/blob/development/public/electron.js#L102 to enable debugging with the background processes that are used to talk to the Python library, just set debug: true
RafaelLeeImg
@RafaelLeeImg
20220225-164229-pslab.png
20220226-184840-pslab-ch2-gain2.png
These are 2 screenshots with analog front end error. The problem is fixed today.
2 replies
20220226-234442-pslab-ch1-gain1-OK.png
20220226-234442-pslab-ch1-gain4-OK.png
These are 2 screenshots with gain=1 and gain=4, amplitude is wrong since the circuit is changed. The wave form is correct.
RafaelLeeImg
@RafaelLeeImg
The problem cause the noise is that when the voltage is low, the amplifier creates a negative voltage, that voltage exceed the working range of MAX5400.
20220226-234931-max5400-retouch.png
That limit is due to there are protection diode on the 3 resistor pins, the diode are added by me on the image.
Daniel aka CyReVolt
@CyReVolt:matrix.org
[m]
Interesting :)
RafaelLeeImg
@RafaelLeeImg
Is there any good way to use a different DAC in this project?
The DAC I'm using is MCP4822 which is a 2-channel DAC with SPI bus.
# pslab-python/pslab/instrument/power_supply.py
        self._mcp4728 = I2CSlave(self._ADDRESS, self._device)
        self._pv1 = VoltageSource(self._mcp4728, "PV1")
        self._pv2 = VoltageSource(self._mcp4728, "PV2")
        self._pv3 = VoltageSource(self._mcp4728, "PV3")
        self._pcs = CurrentSource(self._mcp4728)
6 replies
RafaelLeeImg
@RafaelLeeImg
The DAC with in the current configuration, the supply voltage is 3.3V, the full-scale voltage swing by the current supply can be 20mV~3.260V, but the DAC values cannot cover the full-range of the output voltage.
20220301-141802-pslab-DAC-swing.png
RafaelLeeImg
@RafaelLeeImg
The 5V rail is a little bit noisy.
20220301-165421-pslab-v6-5V-rail.png
That makes the oscilloscope noisy with high gain. The image is showed with the gain of 16.
20220301-162724-pslab-v6-gain-16.png
apoorva-raj
@apoorva-raj
Hi, are the Open Hardware and PSLab meetings happening nowadays?
RafaelLeeImg
@RafaelLeeImg
Why does the LM324 use ±10V voltage supply rail while the output voltage swing is only ±5V?
Can I connect it to ±7.5V?Since the LM324 output range is from Vee to Vcc-2V.
1 reply
20220304-162933-pslab-v6-+5V.png
+5V is significantly affected by the switching cap voltage inverter. Since the operating frequency of 7660 is too low. There is no good way to filter this ripple with small capacitors.
I want to use some other ways to generate negative voltage. I want try buck-boost.
RafaelLeeImg
@RafaelLeeImg
The most obvious noise source on each power rail is from the switching capacitor power inverter.
Since the semiconductor industry is evolving rapidly, the era that use low frequency power converter and big capacitors are already faded away.
RafaelLeeImg
@RafaelLeeImg
The calculation value of voltage ripple is quite near the measured result. If I increase the cap to 100uF, the noise will be several mV, that is achievable but the problem is not solved elegantly.
The current of +10V rail is 15mA, measured with DMM.
Voltage ripple = 1510^-3 mA(1/20000 Hz)/(1010^-6 F)=0.075V.
RafaelLeeImg
@RafaelLeeImg
I'm going to modify the ±6V to ±7V by adding a diode to 6.8V zener diode. The good side is to add a reverse PN node which has a negative temperature coefficient to compensate the
I'm considering to change the U10 OPAMP which used for wave generator to ±7V. Thus, I can remove ±10 rail for OPAMPs voltage supply. The output voltage of ±3V can be covered with this configuration.
RafaelLeeImg
@RafaelLeeImg
I didn't find other replacement of MCP4822. I tried to find some MCU with 2 12bit DAC, for example, STM32L431RCT6 the price is OK (around ¥25), but the stock is only like 100pcs. Or, sample-and-hold amplifier is another option, with that, we can reduce the DAC channel to 2 or 1. That leads to some work on firmware.