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Forum Index : Microcontroller and PC projects : PICOMITE oscilloscope
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| lizby Guru  Joined: 17/05/2016 Location: United StatesPosts: 3013 |
Ah, thanks, gents. Is it likely that this kind of dropper is used in, for instance, the SONOFF ESP8266 switches, where you are warned that if you reflash with perhaps Tasmota or Annex, you must be sure to have mains unconnected since the flashing pins would otherwise be at mains levels with respect to your USB/serial module? ~ Edited 2022-02-01 02:27 by lizby PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 1985 |
yes very likely. The 0V in such cases will definitely be the mains neutral (or live - eek! - if the mains connection is reversed reversed) - you could test this with a DMM... you might see anything from 100R right down to a short between the 0V on a PSU capacitor and the neutral pin on the plug. I personally have no truck with droppers for power. I prefer to use a little SMPSU module to give me what I want but droppers have their place. Nice thing about them is the only variation in size (with current) is the capacitor and that's really easy to accommodate. I consider 90mA to be a practical limit. Also, consider that the current draw "want's to be" constant. With a zener doing the regulating if you have a capacitor so you can get 75mA but your circuit beyond is only drawing 30mA, the rest is avalanching through the zener so it's common to find 1W devices just so they don't cook. Standard precaution. If you don't draw the current (maybe you have a more sophisticated regulation), the voltage will rise - potentially to the peak of the mains (not the RMS because you are using regulated mains - that might be 350V in UK) and you might easily exceed VINmax. All things to be wary of and have caused many a head-scratch over the years. Before I was really comfortable with them, I spent several weekends playing in just about every way I could to fully understand them. The snooker light controller also has an HC-12 in it and I learned early on that I needed a reasonable reservoir capacitor just to hold the juice up for the brief spurts of transmit because the dropper just couldn't supply everything in one go. Not a problem really, the application notes for the HC-12 say to have one anyway, so... On both of the mentioned devices that use the (identical) dropper circuit with C1 to suit, the board has warnings on the silk and then I shower the thing with labels "Warning: all parts of this device should be considered at mains voltage". On the upside; I added to my lab equipment by building an isolation transformer so I can work on the things on the bench  Edited 2022-02-01 03:20 by CaptainBoing |
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hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 705 |
 I can't quite see if there's a place to put an input ? Also if enough info to program ? my site |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 1777 |
One way to get a bit more current, while keeping the capacitor at a reasonable size is to follow the cap. with a bridge rectifier and a 24V zener followed by a mini switch-mode buck converter. While reducing the 24V to 5V or 3.3V it is boosting the available current by a similar ratio, minus losses. For 50mA AC you may get 200mA DC. A suitable electro. across the rectifier DC is assumed. With a bridge rectifier the neutral will no longer be at DC Gnd. and cannot be used as a common reference. Edited 2022-02-01 10:41 by phil99 |
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| KD5ZXG Regular Member  Joined: 21/01/2022 Location: United StatesPosts: 53 |
This link was brought to my attention, no clue if its any good. https://how2electronics.com/diy-smartphone-oscilloscope-using-raspberry-pi-pico Looks like it runs on an Android phone w OTG, Pico just sampling the waveform. Edited 2022-02-04 19:16 by KD5ZXG |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5711 |
Neat. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| geodav Newbie  Joined: 09/05/2014 Location: AustraliaPosts: 12 |
Hi Ztoti, With regards to the rapid A/D conversion, you appear to have made a great scope. Do you have a link to Peters Csub please? All Im trying to do is capture analog at 5 uS/S on one channel only, at present achieving only 10 mS/S in mmbasic, and to only store 200 of these points in an array. Rest of the chip RP2040, will be used for switching various things on and off, with no LCD screen regards George  |
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| ztoti Regular Member Joined: 27/10/2011 Location: CanadaPosts: 65 |
Here is: https://www.thebackshed.com/forum/ViewTopic.php?TID=8070 https://www.thebackshed.com/forum/ViewTopic.php?TID=8074 |
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| hitsware2 Guru Joined: 03/08/2019 Location: United StatesPosts: 705 |
Do You mean : 5 uS = time as displayed on x axis = 1 full wave @ 200 kHz ? / S = 1 second = time spent to get the signal ? vs : 100 Hz ? Edited 2022-02-11 14:49 by hitsware2 my site |
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| geodav Newbie Joined: 09/05/2014 Location: AustraliaPosts: 12 |
Hi ya hitsware, Im in Australia in the Northern rivers and am studying Whipbirds in the rainforest here and have rigged a parabolic microphone for x y z orientation, using mmbasic as the stepper motor drivers. And this works well and fast, however it picks up all birds, therefore I would like to capture the whip bird only (it is the most wonderful sound ever!) and using a Fast A/D converter I can perhaps identify the bird call and then trigger the camera. Therefore I would need to record the sound, identify it from my buffer of previously recorded calls, and click the camera Thus I would require only 5 uS per sample, more would be better but dont know if the the RP2040 can do this. Thank you so much for your reply. Love your work buddy, as I do for our friend ztoti. |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 3505 |
Hi geodav, Nice project. But the sound recognition of the whip bird requires either a reference database and fast sound processing (*), or you would need to train a AI system. Both require more processing power and memory storage than a MMBasic system will provide. You will need laptop power, and with the laptop comes the need for a sound input. There are many USB sound samplers available, from simple USB stick type to the more professional input cards. These would have a microphone input and sample sound at 48 or 192 kHz. Regards, Volhout (*) a way to do it would be to look at the frequency spectrum (fft), and find the section with the characteristics for a whipbird. Then check the envelope of the sound (samples) to detect the rythm. Memory size is important. At 5us per sample, 16 bit (24 bit would be better, but the pico ADC is 12 bit, so needs 16bit storage) 1 second recording requires 400kbyte memory. The pico does not even have that much ram. Edited 2022-02-11 17:55 by Volhout PicomiteVGA PETSCII ROBOTS |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 1777 |
For the males part of the duet the peak volume of the whip crack might be enough to trigger a camera. If the Whipbirds there behave the same as the ones down here (Vic. Dividing Range) the real problem is for the camera to see them through the scrub. They mostly stay in dense undergrowth in gullies. While sitting in such a gully one let rip just 3m away and my ears were ringing for some time. The Lyrebirds do a decent imitation, as part of a 20 min. set covering every bird in the area, and are easier to photograph. |
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| geodav Newbie Joined: 09/05/2014 Location: AustraliaPosts: 12 |
Thanks for the links Ztoti, Using the 28 pin MX170F for the V2 back pack, pins 2 and 23 for AIN are reserved for running the LCD backpack. However, would the Cfunction of Peters see any other analog inputs say pins 3,4,5 as AIN ? Perhaps he is using the Explore 28, which has those pins free and the Option LCD panel configured in another way? I have heard on the forum that some members found it to crash. Best regards Geodav |
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| geodav Newbie Joined: 09/05/2014 Location: AustraliaPosts: 12 |
Hi Peter, you have done a great job with the Cfunction for fast ADC conversion. This appears to be for the Maximite in 2015 and later for the 18 and 44 pin micromite. For the 28 pin micromite using the MX170F on a V2 backpack, which many of us have, AIN on pins 2 and 23 are used for LCD screen, whereas pins 3,4,5 are available for users who wish to make the GUI's for an audio scope. Would it be possible to change the AIN pins only, in the Cfunction? or would the Cfunction automaticaly pick up analog in during the MUX round about sampling? Hope you are safe with the storm Eunice ! regards George |
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| KD5ZXG Regular Member Joined: 21/01/2022 Location: United StatesPosts: 53 |
And I just noticed this. EspoTek Labrador and this... USB Isolator Edited 2022-03-02 19:41 by KD5ZXG |
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Lou Senior Member  Joined: 01/02/2014 Location: United StatesPosts: 229 |
@KD5ZXG How about this one https://www.amazon.com/Quimat-Oscilloscope-BNC-Clip-Assembled-Finished/dp/B07QML4LJL/ref=psdc_256409011_t2_B07CVB7ZJG Lou (AA9RT here) Microcontrollers - the other white meat |
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