PartSim Online Circuit Analysis Simulator by Aspen Labs
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Simulation Program with Integrated
Circuit Emphasis (SPICE) has been around since 1973. The basic computational engine
has always been open source. It began as a simple analog circuit simulator that
took a structured text file as the input net list and provided a text file output
that contained the calculated values that the user specified such as DC bias points,
transient analysis, and AC analysis. Component models started with relatively simple
definitions. If you wanted a graph of the response, it was in the form of text characters
with a standard 80-column division on the y-axis and the x-axis was as many divisions
as it needed to be to cover all the points calculated (often printed out on fan-fold
paper in a pin printer). Yes, I personally used those versions in the mid 1980s.
PartSim Schematic Entry Screen
As time progressed, improvements were added to the computational engine to handle
a wider range of component models including digital and RF/microwave. More parameters
were added to component models to yield a better agreement between simulation and
laboratory measurements. Lagging the mathematical sophistication was development
of a graphical user interface (GUI) for building circuit schematics rather than
needing to enter all the circuit nodes and component parameters manually into a
text file. Trying to keep track of node numbers was a real challenge for all but
the simplest circuits. Early attempts at a GUI were cumbersome and did not provide
a seamless interface between schematic entry and simulation and graphing. Eventually
really good solutions came to the market. Most of the modern circuit simulators
are based on SPICE, with proprietary add-ons in the computational engine. User interfaces
have gotten really nice. The more you're willing to pay, the better the interface
and the calculation capability.
PartSim Transient Analysis Screen
PartSim Report Screen
PartSim Bill of Material (BoM) Screen
Online simulators are now going through the same kinds of growing pains that
the earlier iterations of PC-based SPICE simulators experienced. Most are really
clunky and always seem to be missing key features and/or easily accessed features
- like rotating components on the schematic or routing interconnect lines. Aspen
Labs, in a partnership with Digi-Key, has a free online analog circuit simulator called
PartSim that seems to have
conquered most of the basics. Being able to save and recall your work is a huge
benefit. However, it appears that the file is saved on the website server rather
than on your local machine, so privacy and security issues might prevent a few users
from using such a service regardless of how good it is. I have recommended online
tools to people in the past and have been apprised of the proprietary information
problem. Still, most users probably will not care. One advantage of the online storage
is that it is effectively a 'cloud' environment where you can access your circuit
file from anywhere that has an Internet connection (after signing in with user name
and password).
I loaded the example files and played around with them enough to know that
PartSim is just what the hobbyist
and casual professional designer can use. Simulation time and switching between
screens is slower than with a local program, but that is more a function of your
Internet connection than of PartSim's host server. There is no sense in me reiterating
what has been written a thousand times about how to enter circuits and set up and
run simulations, so instead I refer you to the seven short
online video tutorials to help
get you started. There are some not-so-obvious features that makes it worth your
while to view them. If you are not the type to read instructions, just remember
to right-click and double-click on everything - including interconnect lines - to
find all the options available to you.
I'm not sure why, but the Terms of Use (ToU) state that the user must certify
that he is 18 years old or older. I could understand the need if it was an astronomy
simulator with
naked singularities, but this is puzzling.
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a lady's voice announced "You've Got Mail"
when a new message arrived...
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