Free Virtual Breadboard software?

Shamrock_Don · Post by **Shamrock_Don** » Wed Jan 21, 2009 9:58 am

Anyone know of any software that allows you to create and test simple circuits on a virtual breadboard?

It wouldn't have to simulate microcontrollers - just LED's, resistors, 555 timers, 4017 chips and the like.

Thanks for your time.

tetsujin · Post by **tetsujin** » Wed Jan 21, 2009 10:43 am

Virtual Breadboard looks promising. Personal license is $50. I honestly don't think you're going to find better than that. Though I can't personally vouch for the package's overall quality, not having used it... Try the demo version for starters, I guess. Judging from the user manual, though, it seems like it's a digital logic simulation (as opposed to a real electronic simulation) - and the whole point of it may be just to provide a testing environment for microcontroller source code.

If you want something for free, there's the

http://www.geda.seul.org/index.html wrote:gEDA

package which includes a simulator and some other tools - but we're not talking "virtual breadboard" here - and it may not even have the ICs you want to include in your designs (you could create those ICs using the simulator's netlist language, save 'em as device libraries, and then use them in designs - but I'm guessing the simulators don't include a full library of TTL chips.

Also, when using a simulator package like that, the way you'd work with it normally is set up the circuit and all the conditions for the simulation - run the simulation and then look at the result data. gEDA in general isn't the most user-friendly package out there, and Spice 3 has its share of shortcomings - they're more than sufficient for simulating small, low-speed TTL circuits, though, if you can learn to use 'em.

Going back to the whole digital simulator vs. analog circuit simulator thing I mentioned with regard to Virtual Breadboard - the way a digital simulator works is by assuming you're always working digital circuits in their operating range - so rather than simulate a bunch of transistors (four, I think?) and a bunch of resistors to create an AND gate, it simply uses the logic the AND gate represents. Are both of its inputs high? If so, the output is high (possibly after a short delay). The advantage is that this is very fast, and is sufficient for a lot of what people want to do. The disadvantage is that it doesn't catch degenerate behavior. It probably can detect when an input signal is too fast for the circuit to operate on it correctly, things like that - but it won't be so good at telling you what the circuit will do, for instance, when the supply voltage starts to drop, or if your circuit has any kind of analog behavior (degenerate or otherwise) that has a significant effect on the circuit's behavior, a digital simulator won't show that. An analog simulator (like SPICE) would. Depending on what you're looking for in your simulation that may or may not be sufficient.

Pat Amaral · Post by **Pat Amaral** » Wed Jan 21, 2009 12:11 pm

There are a number of programs available on this site for free. A couple of the circuit design apps look promising. I ordered the CD a few months ago but I haven't had a chance to really play with it. I wanted it so I could try out the PCB layout programs. Most of the applications are engineering level and may not apply to the kind of stuff we do but there are definately some gems in there if you take the time to look.