Posted by: @grossdan

Hello,

I noticed on Ali Express a number of low cost standalone "pocket" Osciloscopes such as this one [1], but, its very hard to know what the quality of it really is, and how "tinkerable" it is.

I therefore keep wondering what it would take to build one own low cost oscilloscope by use of a tiny processor, perhaps, and a simple LCD screen, and writing some software:

Beside tracking a wave, it should also allow freezing or even capturing, a wave window for inspection, as well as support viewing non periodic things such as debouncing waves, capacitor charge voltage and the like.

Would love to brainstorm this -- time permitting, I could also write some of the code as open source.

 

[1] https://www.aliexpress.com/item/1005003632650277.html

[2] https://www.aliexpress.com/item/4000210180957.html

Just my off-the-cuff observations. First they are tiny, second, I have no idea what is required to DIY but when I used them about 60 years ago I recall they were the ultimate tool and cost accordingly. Is it realistic we can build something 'as good'. 

I may of course be wrong, but initially i think I have modest goals.

I want to show my kids a pulse generated by a 555 circuit. I also want to show them how the capacitor's voltage behaves at the input and how it changes with changing resistor values.

I want to show them the "theory" behind this -- how capacitors charge and discharge .

We also played with a switch that activates a shift register only to see that the bouncing causes many shifts -- so seeing a debouncing could be very instructive.

All in all, the adruino IDE already has a simple serial visualizer which presents the values sent from the MCI to the serial port -- while reading, say, pin0 the ADC.

I also noticed an open source library that support visualizing on the host machine and that care of the communication protocol from the device to the visualization client on the host.

So, it seems that some simple things can be done relatively easily on a host.

As a next step, instead of the host, one could try to use an LCD module and display things there, rather than via the serial port.

Dan

@grossdan 

Maybe use this touch screen display shield for the Arduino?

https://dronebotworkshop.com/touchscreen-arduino/

I bought one of these. I find it useful for my needs at the moment, which are very basic as a beginner. You can buy the kit and build it yourself or get a pre-built version. You get what you pay for but it's cheap enough you might be able to fix it if it breaks.

https://jyetech.com/dso-150-shell-oscilloscope/

@grossdan Those are great ideas, I was thinking of something else. Can you tell us the name of the library?

Posted by: @grossdan

an open source library that support visualizing on the host

https://github.com/Overdrivr/Telemetry

I use exactly that oscilloscope (DSO138) for exactly the purposes you have described (debugging 555 PWM timers). One reason for simply buying the kit is that if you get them on sale, you will get the parts cheaper than if you tried to build it yourself.

With that said, there are some real irritations:

• Some of the components in my kit were wrong, specifically, some 100ohm resistors were 100kOhm. Use a multimeter on each piece to make sure it is correct. The kit comes with a schematic you can use to double-check everything.
• The interface is extremely irritating. Too many button pushes to switch between things. There is a github project out there that allows you to swap several buttons for an encoder.
• This is a 1 channel scope... with limited triggering options. That same github project allows you to vastly expand the capabilities of the DSO138 by adding a second input channel. (This will obviously involve extra circuit components)
• I highly recommend putting this thing in a metal box (or a foil-lined plastic-box). Most of the ICs on the board are op-amps, and the long input lines work as receiving antennae for random EM signals in your lab.

(The expanded capability firmware, that will also help give you an idea of what is needed for your own firmware can be found here: https://github.com/ardyesp/DLO-138)

There one that the on YouTube 

Call" the Gadgets"

Give all the info how make one

It Gadgets#62

If you have an old computer or have one on your bench try... 

https://www.amazon.com/Hantek-HT6022BE20Mhz-Digital-Oscilloscope-Bandwidth/dp/B009H4AYII

A little googling I believe you will find many custom application already written that should be fast enough.

Opps didn't realize it would just post a picture. It is a ...

Hantek HT6022BE20Mhz 

You can find it on Amazon for $76 US

These types (plenty of Chinese clones on eBay and Amazon) are just logic analyzers.  IOWs it doesn't do the analog values of inputs... just 0/1.  It has always served me well studying PWM, I2C, SPI, Serial, etc.  It uses an application on Windows (probably others) and has many features including triggering, and translating (taking I2C, SPI and translating it into the ASCII).

https://www.amazon.com/HiLetgo-Analyzer-Ferrite-Channel-Arduino/dp/B077LSG5P2/

Interesting - I put an Amazon link to give a reference and it dug the picture out, but not the link.  Pretty cool, but doesn't help you find the part.  It's about $12 on Amazon, cheaper on eBay and does 24Mhz sampling on 8 channels.

I'm hardware challenged, but I'd like to join any effort to design an oscilloscope capability.  I started scoping out how to do a logic-analyzer just using an ESP8266.  The problem with even a logic analyzer with a microcontroller, is the one micro-second resolution (1MHz)  That might be useful for many projects???

I "think" doing an Oscilloscope only makes the hardware side more difficult.  Software... not so much.  Doing high rate analog readings with say an Arduino... the readings analogRead() takes a long time.  Is there some hardware wizards that can suggest some high-rate A2D components?