martin changed the title to Homemade oscilloscope to detect PWM DIY guide .
Homemade oscilloscope to detect PWM DIY guide
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martin The BPW 34 seems to be pretty fast. 100 nanoseconds rise/fall time for the Vishnay Model, 200 ns for OSRAM's. I found this link where someone further explains those values: https://electronics.stackexchange.com/questions/118141/high-frequency-blinking-leds-and-sensor-for-that
The OSRAM BPW 21 you mention seems to be much slower - 1.5 microseconds, which are 1500 nanoseconds:
https://www.osram.com/os/ecat/TO39%20Ambient%20Light%20Sensor%20BPW%2021/com/en/class_pim_web_catalog_103489/global/prd_pim_device_2219533/ (There's a linked datasheet PDF with specs)
OSRAM BPW 34:
https://www.osram.com/os/ecat/DIL%20BPW%2034/com/en/class_pim_web_catalog_103489/global/prd_pim_device_2219534/
The next step might be those more expensive photodiodes. Somewhere I saw a price of $40. But maybe that's overkill. We better upgrade our oscilloscope first.
The cheap Hantek 6022BE USB oscilloscope has sample rates of up to 48 MSa/s. Compared to 44100 Hz of our sound card, that'd be a big upgrade.
www.amazon.com/Hantek-HT6022BE20Mhz-Digital-Oscilloscope-Bandwidth/dp/B009H4AYII
It even has an open source project with Linux and Mac support: http://openhantek.org
KM Ask @TechSensitive about oscilloscopes. He might know.
martin Not sure yet. It looks like it has two connectors. Maybe holding/taping them at our audio cable would work. But I found hints at German forums that an additional amplifying circuit may be needed:
https://www.mikrocontroller.net/topic/417617 English translation
https://www.prad.de/board/thread/50411
English translation (bottom of page 1)
KM Might be. @TechSensitive , could you shed some light on this? Just a photo of how your setup maybe looks like with a small explanation how the photodiode is attached, would help a lot.
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martin I got the oscilloscope today. It has a "crocodile" and a hook connector:
Short impressions so far:
- The output is more accurate than (my) sound card oscilloscope. One can actually see the "zero" axis and judge how big the difference in amplitudes is. Plus the waves resemble reality much better.
- The Hz counter of the OpenHantek software is worse than the sound card scope. It seems to count only very obvious sinus waves. I.e. when the PWM almost touches the x-axis. Not sure yet how to change that.
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Hello, i'm using a similar setup with the Hantek 6022BL and a OPT101 (https://www.ebay.com/itm/232458733138).
This chip includes a photodiode with a transimpedance amplifier which greatly simplifies the schematic needed:
For the software i would suggest the great PcScope made by Fabio1963 (https://www.dropbox.com/sh/qieod71ucovd6we/AADJvoBmMZNcR0kFB8ysS7vSa?dl=0).
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Amazing. Could you test some of the newer iphones, in case they give you eyestrain as well? Im gonna do that on my work iphone where I have absolutely terrible and long lasting pain.
Yes the software looks crap compared to Zeitnitz. Also we might need to get a better photodiode just to be sure. I was recommended this - https://www.conrad.cz/pin-fotodioda-osram-components-bpx-61-to-39-vyz-uhel-55-400-1100-nm.k153122
@Wootever please what is the difference when you use the diode with the circuit as bought from ebay?
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martin
The transimpedance amplifier converts current from the photodiode to a voltage usable by the oscilloscope (it basically amplify the signal for a more stable output).
The advantage of a combined/embedded design:
The integrated combination of photodiode and transimpedance amplifier on a single chip eliminates the problems commonly encountered in discrete designs, such as leakage current errors, noise pick-up, and gain peaking as a result of stray capacitance.
9 days later
For Android there's an app called "HScope". It supports various Hantek devices, including the 6022BE. My first impression is that it's great software. It detects frequencies much better than OpenHantek does and generally seems very polished. We might be able to create a portable solution with an Android device, a USB On-The-Go cable, a power bank, 6022BE + probe, and the HScope app.
HScope App: https://play.google.com/store/apps/details?id=com.martinloren.hscope
Guide: http://hscope.martinloren.com