I don't know if you've seen this video, but W2AEW did this on a breadboard:
I'll have to say, that yours is the nicest looking one using this simple design. I'm going to box up my cobbled together version, but it will be in a plain looking project box
Of course, the idea of a curve tracer (octopus) is quite old. There are several ways to make one. Years ago, I made a traditional one, using a 6 V transformer.
I've been playing about a bit with scope settings and resistor values. First, I found that you need to use DC coupling, as AC coupling will cause the trace to move downward when you attach a component, like a diode.
I decided to only use 3 V from the SG, as this is enough for even LEDs, but not enough to blow up 3.3 V ICs. With this change, I had to go with a 47 Ohm resistor between the SG and Ch 1. I set Ch1 (X) to 500 mV/div to get more resolution on the voltage knee for diodes. I set Ch2 (Y) to 50 mV/div to keep the trace on the screen, with the voltage and resistor I am using. The 200 us that you used still works fine.
My mistake. I forgot that the sinewave is 5 Vpp, not RMS. At 5 V, it wouldn't work with a blue or white LED.
Thanks for posting about your version. It integrates very nicely with the Owon scope.
I hadn’t seen that particular video before, I looked at a couple of other similar ideas though.
I own an octopus tracer and a couple of real scopes, so my use case for this wasn’t to replace those. Nor was it to even attempt to replicate the increased functionality that us possible when you have PSU/transformer to play with.
Rather i was looking at what was possible using just the built in functions, specifically not needing extra cables or a psu. Being a portable scope, it seemed most useful to be able to use the tracer adapter without then needing power or carrying a lot of extra pieces.
This way it can be used not just mobile but also when operating isolated from mains ground is important.
Also as it seems like a lot of beginners might have the HDS as their first and only scope, and likely not also own an external sig-gen, so it should work for them also.
As it turns out though, you can separate it from the owon, connecting X and Y with bnc cables, and use an external sig-gen to provide a 12V or greater sine and you can then view zeners above 5V etc also.
I am thinking of adding a dedicated bnc for that on the banana side with a switch to selectand a higher value series current limiting resistor.
btw,if you want to use the enclosure I found that almost exactly matches the owon dimensions, you can get it from Amazon or at least get the specs from the listing…
https://a.co/d/9SRdW1Zand bnc couplers from Amazon come in sets of 5 cheap, they are made of crappy pot metal but saves me keeping 3 of my real ones in the a kit that’ll only get used occasionally
https://a.co/d/5z3ZSV2