A tale of two sims...

Disclaimer: This is only to alert you to something you might want, and to give you some information which may save you wasting time. I get nothing from either program's owner, so I'm not triple checking each point made for accuracy. I hope it is of use to you.. and if it isn't, it's worth what anyone paid me for my work!

I've tried two shareware simulators of digital electronics. Each is usable, each has shortcomings. I think either is suitable for use in schools for 9 yo and up... but see below. Either would be of some use to adults interested in digital electronics.

Installation, etc, of neither is as user friendly as it might be, but hey!, they are shareware!! Do you want a simulator or not? Using them is straightforward, once you get used to them. First complaint: I couldn't find on-line contact channels for either.

They are:

Digital Simulator (DS) 1.0, by Ara Knaian in MA, USA
EasySim (ES) from Research Systems in Australia

I've run both on a Win98 machine.

DS is advertised as being for Win95. Registration is $20, US.

ES is a Win 3.x program, but runs on Win98, as I said. Registration costs are given in Australian dollars: $A50, plus they want $A15 for p&p to non-Australian addresses.


Both give you a worksurface onto which you place digital electronics elements by clicking on what you want from a 'palette', and then clicking on where you want it. Both offer AND, OR, NOR, XOR, etc gates. Both have flipflops and latches and 7 segement LED displays. You then make connections between the elements.

Both work in two modes: design mode and simulation mode. You set up the circuit in design mode(DM). You then see what it does in simulation mode(SM). In SM, you can change the state of inputs by clicking on them. I liked DS's inclusion of toggle switches (stay '0' or '1' after being clicked) and a momentary switch which outputs a '1' only so long as you keep it 'pressed' with the mouse. Clever: If you double click the switch it changes to producing a '1' UNLESS you have it 'pressed'. Rough edge: There is no difference in the icons for the two sorts of switch.

DS seemed much better on dynamic circuits, as far as I explored the two packages. It has a square wave generator, with variable frequency and duty cycle.

'Wiring' together the elements was quickly easy in ES, but not hard in DS. ES has a nice 'logic trace' feature that highlights any wire with a '1' in it (if you wish. Can be turned off.)

The good news... DS is cheaper than ES.
The bad news... it is more prone to crash. Annoying, confusing, etc, for the less didicated/ confident user. It was also capable of displaying things which looked wrong to me. Probably best used in schools with teacher support. The more expensive, more limited, ES I would happily provide to unsupervised 9yo. (I would want to introduce them to it, but wouldn't feel they needed even that.)

How to get them...

I obtained Digital Simulator from PDSL (www.PDSL.com\, I think... they have a site, but not a download site... you have to order by snailmail) The Public Domain & Shareware Library, PO Box 131, CROWBOROUGH, E Sussex, TN6 1WS, England, Telephone: 01892-663298 Fax: 01892-667473

Digital Simulator is their ref N005043

The program refers you to...
Ara Knaian, 38 Llewellyn Road, Newton, MA, 02165, USA, (617)964-0299 (tell him about this review, please?)

- - - - -
I found EasySim by searching the ZDNet download archive for Windows digital simulators. The download was only 91k. If you click here, it might take you to the Ziff-Davis EasySim download page. Alternatively,

Click here to access the front page of Ziff Davis's excellent shareware archive/ search engine.

If you want to send some snailmail to EasySim's people.... (tell them about this review, please?)... the address is:

Research Systems Pty. Ltd.
15/1540 Main Road,
Victoria 3095,

Fiddly bits... random thoughts, etc....

I had minor trouble with the installation of ES. Seemed to unzip, but the 'files' were empty. Probably something to do with trying to install to a folder which held the folder I had the zip file in.

Neither offer rubber banded dragging of components.
DS doesn't even offer dragging at all... you have to cut, then paste. On limited use, I found getting what I wanted marginally easier with ES.

DS uses a green circle to say '0' and a red circle to say '1'.. for inputs and outputs. ES uses '0' and '1' to mark inputs, and a 'lamp' which is grey or yellow to display the state of outputs. (I prefer the latter.)

DS offers a logic analyser... I didn't get it to work, but I didn't try very hard! It is supposed to monitor multiple signals and display state against time graphs. Pretty snazzy! Typical DS: more ambitious. When the bugs are out, this is going to be a great program, and the price is great, too.

Edited quote from a file which came with ES:

"EasySim is a digital electronics simulation package. It allows digital circuit designs to be designed and tested in a windows environment. It gives the user a selection of logic gates and flip flops along with various input and output devices, thus providing building blocks to emulate logic functions.

"The product is aimed mainly at the educational market but will also be of value to the electronics enthusiasts wishing to test out small circuits before committing themselves to wiring up a circuit."
<end of quote>

Click here for information about another logic simulator, Virtual Workbench.

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