How to get continuous time display for oscilloscope?

I searched already and couldn't find an answer.

I have a circuit that generates a ramp wave. The circuit works on other simulation software, and it works in real life as I've built it before.

When I attach a probe to the output, I get a DC signal. I am assuming that the scope takes a snapshot for something that it thinks is DC, and a time axis if it detects a dedicated AC signal.

Does anyone see anything wrong with the parameters I have specified? cap=2.2nF, R=1k.

The voltage follower simply copies the signal to ensure there is no short to ground.

Thanks fellas, ya'll are baller.

[Sabin]

Could you attach the model rather than the print screen? Will be easier to investigate as we don't have all the information.

[Will Banks]

yes, here you go. thank you

Answer 1

[Joel Van Sickel]

Looking at this circuit, shouldn't it require an inverting trigger to work correctly?

[Will Banks]

yeah you can use a NOT gate if you wanted to. That is what I did in multisim. Schmitt triggers are really similar, and I can confirm that this circuit works in real life with a schmitt.

at time 0, theres no volts at the junction, which initiates a positive voltage on the capcacitor which charges the capacitor. once the threshold voltage of the NOT/schmitt is release, the capacitor discharges through the resistor, creating a sawtooth waveform that oscillates.

I showed this issue to my professor, and he wasn't able to figure it out.

[Joel Van Sickel]

What I meant is that the schmitt trigger in the Simscape library is not an inverting Schmitt trigger. I believe you need an inverting Schmitt trigger for the behavior that youre describing.

[Will Banks]

ohhh i see what you mean! so, in real life, I used the CD40106 schmitt trigger, and you're right! the CD40106 is an inverting schmitt trigger.

Now, that leads to another question. Is there an invertin schmitt trigger, or an equivalent in simscape? In multisim, I am able to create the sawtooth wave with a NOT gate. But have had issues with this as well on simscape. That is a detail I forgot to mention.

any tips? thank you so much for your feedback so far. I really love this software ever since it was introduced in my electronics class.

[Joel Van Sickel]

I'd be interested to see why the not gate doesn't work, but let's assume that won't work based on what you've seen, so you could feed the original signal into a not gate, and then feed the not gate results into the schmitt trigger, essentially creating your own inverting schmitt trigger.

I tried parameterizing the schmitt trigger as if it were inverting, and it wouldn't let me, which would have been a nice alternative.

You could also try and find a spice model of the trigger you used and use the subcircut2ssc command to import that into simscape.

[Will Banks]

boo yah! some real progress here. this isnt the result i want, but i may be able to change the parameters a bit to get what i want.