Hi all,

I'm not very experienced with electronics, I'm a programmer by trade... which is why I always resort to using a microcontroller whenever I have an electronics project :)

I've noticed that others on this forum also seem to be very new to electronics, so I thought I would share a tool that I used to "prototype" all my electronics designs before I build them for real:

http://www.falstad.com/circuit/

Sadly it does require Java capable browser to run... Anyone here able to port it to Javascript and HTML5 (Then I could run it on my iPad)? I have no Java experience at all...

Anyway, this allows me to check my resistor values are correct without burning out real components... so it's worth using.

Here is my "prototype" for driving a small electric motor using one of the Mbed's digital out pins (actually a PWM pin, but that's not important).

The Mbed can only source about 40mA from a single pin, so in order to drive an electric motor, one needs to use a transistor... The only transistor I had lying around were some BC337's, which are pretty normal NPN transistors, but the maximum current they can drive is 800mA... so I used this tool to find out what value resistor I needed on the Base... as the 5v electric motor I use had a resistance of 2.2ohms, I decided to use 400ohm resistor... which, if I've understood everything, will mean the maximum current through the transistor will be 654.5mA... Hooray! That gives me a 145.5mA tolerance for variance in the components :)

See below for a screenshot :)

/media/uploads/bloodline/mycircuit.jpg

-Edit- I've modeled the electric motor as a 2.2ohm resistor with a flyback diode, which I included in my design to protect the transistor from any reverse current off the motor (which I know happens with solenoids... not sure about motors).

Here's what I find to be a powerful simulation tool (but less animated). To address the learning curve there are tutorials.LT Spice

@Matt, This is a Windows program, so still won't run on your iPad.

Actually, there is iCircuit on the iPad... but it's not quite as good as the web version :) Also I'm in a Mac household, my last WinXP install died earlier this year... I have no plans to resurrect it, but thanks for the link ;)

This is cool important tool, would be cool if it was downloadable as well:)

Well, it would be nice if the Mbed IDE was downloadable too... but at least these tools are platform independant.

Hmmm, I downloaded the zip of the circuit simulator website and it runs just fine off line. FTW.

LTSpice runs very well on Linux using Wine. Apparently the LTSpice maintainers have been taking bug reports for Linux/Wine, and they try to keep it running there as well as on Windows. Your Linux distribution probably already has Wine; just download LTSpice and type "wine LTSpiceIV.exe" at the Linux command line and you're off and running.

It only goes upto 25khz do you know of any going upto 100khz.

This version of the same circuit simulator does go upto 100khz

http://www.alternate-energy.net/aps/sim2/index.html

v1.4f

What up with this Matt

Exception in thread "main" java.lang.NoClassDefFoundError:

Caused by: java.lang.ClassNotFoundException

at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) Could not find the main class:

With LTspice does somebody know how to get it to view more than one frame in the Wave viewer or can it not be done... for a op amp. Andbody know any simualtors that it like the falstad..

Ya know continuously simulation of the wave form the sine wave.

Doctor is here Philips don't worry I will fix it:)

Doctor:Philips talking to yourself again

Philips: Afraid so

Philips: it was the Stop Time.

Doctor: Yeah I see:)

Philips: Had to increase it. I am a bit of a speed freak tho:) I like the speed of falstad, all tho it lacks some electronics

Doctor: :D

http://mbed.org/media/uploads/mbed2f/stop.jpg