Circuitlab.com launched - Great & Free

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Hi Bob,

One of the developers of CircuitLab here. Thanks for the link! Been a diyAudio lurker for a while now :)

We'd definitely love to hear from the diyAudio community about how we can make this into a tool that would be awesome for everyone here. When I browse through some of the Solid State forum posts and see lots of different schematic images that are purely static and are clearly made with a bunch of different, incompatible, non-cross-platform tools, it really makes me think: why can't each of those schematic images link to an editable, simulatable circuit that someone else can change/fix/simulate/save and post the new version back as a reply?

Our site has only been public for two weeks now, but we've already been featured by a variety of places like Slashdot, Engadget, the ARRL, Nuts & Volts, EDN, ... and hopefully we're on the way to building that vision!

As far as "free (for now at least)", we've said that "it has always been our intention to keep the core functionality free, for the benefit of the greater online electronics community." (See our FAQ). This kind of tool is something we think has been missing online for a long time, and our NerdKits microcontroller kits business pays the rent and has funded the development of CircuitLab.

Mike
 
Hello Mike and thanks. Like most people here I use LTSpice, but unfortunately I have to boot up the old PC, so It will be nice to simulate on my mac!

Any chance you can summarize the similarities/differences between LTSpice and circuitlab? Which should I use when? And is there a way to use my LTSpice ccts in circuitlab?
 
OH I didnt know Circuitlab ran from your web browser. Thats cool. You can run it anywhere theres a computer.

Now answering my own question: It trades power (LTSpice) for ease of use, convenience and sharing. ie great for quick sims but not power use (eg FFTs from power amp circuits).
 
Yup! Both the schematic editor and simulator are 100% browser-based (javascript). No installation necessary, as long as you've already got Chrome or Firefox.

"ease of use, convenience and sharing" -- better than I could have put it!

If FFT mode for distortion analysis is the missing ingredient for this to be a really useful tool for the diyAudio community, then I will definitely investigate adding that to CircuitLab. We have a big to-do list right now, but that sounds like a really useful addition both for the audio community as well as the RF users.
 
Perfect!

Thanks, this is. perfect! :) I tried using the DigiKey's SchemeIt, which was nice, but i haven't found a "GND" symbol anywhere which rendered some circuits meaningless. Browsing thru symbols was pretty painfull too.

Yours site is great, clear and easy!

I really miss the "Spacebar rotate" key i used to in Altium and MicroCap. Is it possible to make the spacebar rotate components, or the browsers won't pass "spacebar" key into the apps?
 
Thank you, Thank You, THank YOu, THANK YOU!!

Aimed right at Compumike. What a great thing you have done for us Mac users.

Yes, I can kick up Parallels or Bootcamp and get Windows rolling for LTSpice, but your simulator is easy and effective for lots of things and easy to get at in the Macworld.

I'm no great expert simulation geek, but I admit that I miss stuff when I try to design a circuit on paper. Doing a basic simulation helps me see my errors and your easy approach is just what I need.

I like the Frequency Domain Simulation, but would like to confirm what it means. I think you are stimulating the circuit from the input point with a small signal and sweeping through frequencies. Can I interpret that as small AC signal noise rejection for a DC voltage regulator output?

One suggestion. When I make a mistake or want to change an approach, deleting elements in the circuit involves going up to the Edit box many times. A "right click" on a "red" highlighted element with an option to delete or cut would be great.

Anyway, thanks again.
 
3rd Party Models

Thinking about CBDB's suggestion for 3rd party models. Maybe there is a way, if the CircuitLab guys are willing, to do some kind of Wiki approach to the model library.

Let's say I want to use an opamp that isn't in the list. I go find the datasheet and put the specs for the desired opamp in the model specs. I rename it to the new opamp and save it. That's all there in CircuitLab now, but I think the new component stuck in my model.

Step one would be to identify newly created component models in people's circuits and make them available in the library, maybe in a different color so that people would know that it was a user created component and should be checked.

Step two might be to see if there was more complete model information that could be used in CircuitLab . The simulation does a lot right now, but there does seem to be a gap between the component descriptions in CircuitLab and Spice. I'm not sure what is possible here.

Anyway, what is already there is great. Like CBDB, more components would be great, but then more is usually a good thing. Thanks again.
 
lehmanhill, as far as your frequency domain question, it really depends on your exact circuit. Some device models like the linear voltage regulators don't have any modeling of the coupling between input and output (so long as you're above the dropout voltage!). And for AC-to-DC circuits, like a diode rectifier, the DC operating point won't reflect the "charged" or "periodic steady state" condition of the system, so that wouldn't show you a true measure of power supply noise rejection. But if you're trying to model an input DC source, maybe a diode / inductor / resistor / capacitor bit of input filtering, then yes, you'd be able to learn something about noise rejection by using the frequency domain simulation for small AC signal noise rejection. Post a link to your circuit so we can see!

Deleting a selected element can be accomplished quickly via the delete key on your keyboard. Right-click menus may come in a later version.

untangle -- thanks for the blog post!

As far as third party models, shareable parts, etc: yes, we know we have to find a good way to let users share these part models. Having the components not be "stuck in my model" is certainly an important feature that we need to get right. For now, there is a copy+paste option -- you can open someone else's circuit with a saved custom op-amp or BJT, and copy and paste it into your own. (What kinds of SPICE model features are we missing that are most important to you?)

In the short term, if you have specific audio-related part numbers you'd like to see, let us know on our site -- someone posted this list of "universally favoured BJTs for analog DIY audio amplifier projects", and we're looking into adding them shortly.

Thanks all!
 
Voltage Regulator to try Frequency Domain

As Compumike requested, here is my CircuitLab link. This is a variation of a voltage regulator used by Jos van Eijndhoven in this Relaixed2 balanced preamp. I'll post a build report on that when I get a chassis built, but for now, this was a great use of CircuitLab. I was trying some ideas using Jos' circuit as a starting point. The ability to model it and to share it with him through the internet was great. More than that, he could modify it, either to show me where I went wrong or to try something new.

As for the simulation, try the Frequency Domain simulation. As Compumike says in an earlier post, the noise rejection capability is very useful, as long as your are careful.

 
Folks, I am one of the developers of www.DoCircuits.com We are also trying to create an online web based circuit simulation on the cloud - and modeling real devices and components. Its still early - and we have a load of components to add, etc. I will be very grateful if some of you can give it a spin and give your comments. :)

I wish you could put your build on the frontend of LTSpice. Nice work...

What will be the price when it is done?
 
DoCircuits.com

Thanks ! The only issue is that LPSpice is proprietary - we would have to go and talk to Linear technologies. NGSpice would be much easier since its Open source. We plan to keep a basic version of simulation free and charge for an offline model - like on the PC / Ipad, etc.
 
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