Learning electronics

[Jmsteele187]

I've been trying to learn the ins and outs of guitar effects electronics for a while.  But I feel like I need to take my knowledge further.  I can read schematics, I've also been modding pedals for a few years now, and I've built a handful.  However, when I build something, I'm always copying something someone else has already done.  Which is fun, but I'd like to design my own circuits.  Can anyone recommend some interwebz reading that will give me an understanding about how all these circuits work, so I can start coming up with my own toys?

[Brisance]

Get a simulator, even an online one, draw your favourite circuit and start tweaking, that will teach whats going on there.

Also get something like "The art of electronics" book, that's a great read.

[Jmsteele187]

Tell me a little more about these simulators.  Do you just put in a schem, and it simulates how it works?

[Brisance]

Yes. pretty much, for simple concepts, http://www.falstad.com/circuit/ is a pretty nice online tool, I have learned a lot using it. Going more advanced, there's stuff like LTspice and TINA, which do all sorts of stuff like stress analysis, tolerance worst case schenario etc.

TINA: http://www.designsoftware.com/home/English/&
LTspice:
http://www.linear.com/designtools/software/

Examples:

Currently designing a distortion with TINA, here's the input and output superimposed:

Here's the frequency response curves for it:

[PRR]

> I'm always copying something someone else has already done.

EVERYthing in small audio has already been done. (A dozen exceptions in the least several decades.)

Plagiarize. Understand. Modify. Shamelessly.

[tca]

> EVERYthing in small audio has already been done.
I agree with that statement. But should I ask: what do you mean by small audio?

[MaxPower]

^Had a witty rejoinder for that but figured some might take it wrong.

I recommend the textbook: Electronic Principles by Malvino. For what it's worth, I found Tina-ti easier to figure out without reading any manuals (what manuals?) than LTSpice.

[Jmsteele187]

Thank you guys.  When I get a chance, I'll take a look at those simulators, and look into a couple books.

[Jmsteele187]

Ok, so I've downloaded LTspice and I've been messing around with it.  It seems pretty useful.  I do have one question about it though.  How do you make a potentiometer or variable resistor (whatever you want to call it) in the program?  Also, I decided to download the freeware version of EagleCad.  I'm not sure how to run it though.  After download, there were just a bunch of folders all over my desktop.  If you haven't guessed, I'm not the most computer savvy person out there.

[Brisance]

IIRC theres no pots in LTspice, but there are in TINA. Workaround is to replace it with 2 resistors

[Jmsteele187]

I'm assuming you'd run the resistors in parallel, and label it accordingly on the schem.

[Brisance]

In series. That's what a pot basically is, two resistors, center tapped

http://en.wikipedia.org/wiki/Potentiometer#/media/File:Potentiometer_with_load.svg

I suggest you start with the online simulator for the basics, it allows you visualize the voltages and currents in real time

[Jmsteele187]

Ok.  Now I feel a little dumb, lol.  That makes perfect sense.  How would I determin the size of each resistor?  Say I wanted a 500k. 

[Brisance]

Depends on the setting, they need to sum up to 500k. A 500k pot just wipes the center tap along a 500k resistor, leaving amounts of that 500k to either side.

[Jmsteele187]

thanks for the help!  I'll try adjusting the the values to see what I get in the sim.

[GibsonGM]

With some hunting, you can find a pot model that simply *works*, with no "include" statements to need to remember.   I forget just where I got mine, but it works just like any other component.    There is some stuff here on it:  http://www.diyaudio.com/forums/software-tools/230071-ltspice-potentiometer.html

I know it's a pain to set that up, but well worth it, and also teaches you how to add stuff to LT.   Come back with questions

Generally, you have to place a symbol file in one folder of the program the 'definition' in another...read the post....

[GibsonGM]

And HERE: http://forum.allaboutcircuits.com/threads/importing-models-into-ltspice.36456/  Sign up free if you have to...look at Post #15!   

[Thecomedian]

thanks for the help!  I'll try adjusting the the values to see what I get in the sim.

The way I do it is node to the next stage or cap or whatever from between the series resistors which implicate the "pot", then shift the numbers from 500k on bottom and 1 ohm on top to 500k on top and 1 ohm on bottom, to indicate the wiper going from "10" to "0".

The resistance through the pot to ground should always be constant, while the resistance shifts for the wiper from 0 to the circuit to 0 to ground, with the other side being the opposite.

[GibsonGM]

Once you figure out how to add a "real" pot, it's MUCH simpler, IMHO. You can sweep the wiper, no 'extra' math or anything.   Well worth looking around the links I posted to see how it's done.

I did it about 5 yrs. ago, and forget now, but recall all I needed to do was place a few files in some subdirectories, and the program recognized it, includes it in the components list (no .include needed).

[MaxPower]

As stated previously by someone, Tina-ti has pots. You might also give Multisim Blue a try, it also has pots.