Darrell, thanks.
I will get to know more about it, but the online system seems eating too much resource for my old xp computer, so I may use offline function to try.

@ScottWang Are you by chance trying to use Internet Explorer as your browser? SystemVision works best using either Chrome or Firefox browsers. Most of the required computing horsepower is in the cloud, so your xp computer should be fine. You just need a browser and a decent internet connection.

 

If you want to get a 20V dc for the motor, you may consider the Vac decrease to 16 Vac, Vout_dc = 16 Vac*1.414 = 22.6 Vdc.

And the circuit you may change to this way.

There's a better way of doing the 2 diodes that gives a wider variation in PWM ratio.

Eliminate R2 and put the pot track between the bottoms of the 2 diodes, the wiper goes to the timing cap.

 

There's a better way of doing the 2 diodes that gives a wider variation in PWM ratio.

Eliminate R2 and put the pot track between the bottoms of the 2 diodes, the wiper goes to the timing cap.

I know the circuit you mentioned, but I think you didn't see the post #9, the circuit you replied to is a 50%/50% duty cycles pulse(square wave) generator, it is not a pwm control circuit, if you adjust the pot that it is changing the frequency and it is not changing the duty cycle.

 

Darrell has been promoting the SystemVision simulator here so this is my initial observation on that:
SystemVision appears to be a general purpose cloud simulator that does more types of simulation as compared to Spice but does not use as elaborate part models, so the simulation accuracy is likely not as exact (for example the op amp model uses basic parameters from the data sheet and is not a transistor level model, and the digital models are generic).
But this means that it should be relatively easy to generate new part models from the part data sheet as compared to Spice where it's kind of a pain.
For many applications, particularly on this Forum, I would expect its accuracy is likely sufficient, and it probably simulates more rapidly and may be less susceptible to the simulation errors that Spice is known for.
It also looks at the components' stress levels which Spice does not.

(Darrrell, please feel free to comment if my cursory comments are in error or you would like to elaborate).

@crutschow Thanks for your comments! SystemVision is indeed a versatile general purpose simulator. It's a cloud version of some of Mentor Graphics most powerful and detailed simulation engine technology.

As many people are aware, SPICE was originally created for IC design (Simulation Program Integrated Circuit Emphasis).
Many resourceful and innovative individuals have adapted SPICE technology to model non-IC devices, which (as you mentioned) is quite a pain! The SPICE transistor models, for example, have parameters related to the physical dimensions and properties of semiconductor structures. This information is not typically available to the person trying to fit the available IC parameters to the non-IC device (and is proprietary information when it is available). So what do they do? They do some kind of curve-fitting to get the best fit that they can. The accuracy of this approach is pretty coarse. This task is often outsourced to 3rd parties.

We could have done the same thing in SystemVision, but we have seen the frustration of engineers when the discover that the SPICE model for a part that they are using doesn't match the datasheet for the part. We took another approach: we created new models where electrical behavior of the model maps directly to the datasheet parameters. This could be done in SPICE too, but it is typically too difficult because the device models in SPICE are hard-coded into the simulation engine. With SystemVision, the models are external to the simulator, written in an IEEE standard modeling language (an extension to VHDL called VHDL-AMS).

These models are all available online, on systemvision.com. You can use them without having to know anything about writing models, just like you would in a SPICE tool. They are, however, open-source, if you want to see inside (or even modify/improve them). We provide a tool that presents you with a datasheet representation of the device. You fill in the values and we make the model for you. This includes part ratings as well, so you can easily see if your design will stress the parts.

Digital models can be represented with the full richness of the VHDL language. We provide a library of common gates, flip-flops, latches, etc., for convenience, but there really is no limit to the complexity of a digital component. You can modify ours or create your own. The 555 timer model in this thread uses both the analog and digital constructs of VHDL to implement the model. It's really pretty straightforward.

This is a big topic and I have probably already side-tracked too much from the main topic of this thread. We have created some videos that go into more detail for anyone interested in understanding it more: https://www.systemvision.com/webinars

 

Hi Darrell:
Maybe you can create a new thread to discuss about the System Vision, what do you think?

 

sorry havent had time to get parts or reply, no work tomorrow so i will go pick up smaller resistor as well as an IRF540 to test things out. by the way, i originally was using a 10Ohm resistor on output of 555 as per something i read online, but that fried my 555 for some reason, as soon as i switched to a bigger resistor, that cured the problem, maybe resistor too small lets the transistor pull too much current from the 555 or something?

 

Did you see my posted in #6, if you used 555 then what should you do?

 

well that was before i started this thread, dont even remember where i read 10 ohms, ill go for 100 O then