Noob question about schematics...

[electricdave]

Hey everybody. My name is Dave and I hope nobody minds a noob question about schematics.

I purchased a few books that I'd hoped would help me learn to build projects using schematic diagrams. The first, and most basic and helpful, was Electronics for Dummies, which was written with know-nothings in mind. It's been very helpful and enjoyable but I have a few questions.

http://www.makezine.com/images/09/Cr...xAmp_Schem.pdf

In that schematic, there appears to be no battery or power source, no speaker, and no guitar input jack. There is something marked "in", something marked "out" and a 9v power source, but the problem for me is that a speaker has two connections, not one as shown in the "out" and a jack has two connections, not one as shown in the "in", and the same with a battery. I'm assuming that the conventions for reading this schematic are simply different than the very basic ones in the books I have here, but I still don't know what they are how to read it or build the project. Also, the books I have here say that a triangle is a ground connection. Is that the case here? If no, what do the triangles mean?

Thanks in advance for any help and I apologize for the noob-y ness of the question. If anyone has any suggestions for reading materials that would help me understand schematics not written in the basic way in the books I have, that use various forms of shorthand, which must be what this one does, instead of writing everything out, I am all ears.

Dave

[electricdave]

While I was waiting for a reply, I thought I'd get out the Dummies book I have here to see if it had an answer. Well, I look at the project list and there is an LM386 amp similar to the one in this schematic. And the schematic in the dummies book, like the one I linked to, doesn't show every single thing; it too is written in shorthand. Therefore (he reasoned) since it *is* a Dummies book and they tend to be well written and logically written, the book itself must explain the shorthand. I went back to the "reading schematics" chapter and lo and behold it says that sometimes in a schematic each and every connection isn't shown--for instance, the negative lead to a battery is often connected to a common ground, as is the negative lead to a speaker and so forth, and that in a circuit like the LM386 amp, ground is a common point, a common connection--ie all "ground" connections are to the same physical place. The schematic will often assume that the builder *knows* this and won't explicitly show it. Well, that makes the schematic I linked to easier to understand.

Okay. Now I gotta wait for Radio Shack to open because there are a couple of parts I need.

Dave

[oc disorder]

You're on the right track ..there can be variations in the way circuits are drawn.
Here's a similar circuit using a LM386
http://www.electronics-lab.com/projects/audio/044/
It shows connectors for the input,output and power.
Also has an on/off switch and a led indicator to show its on.

The manufactures data sheet for the IC also usually gives examples of how to wire the chip.
http://www.national.com/ds/LM/LM386.pdf
It also shows a "block" diagram of the chip and the pin numbering.
Pin 4 is shown as a ground conection.

Its a matter of building up knowledge through practical application and trial and error ..failure can be a great learning tool although frustrating.

When looking at a complex circuit it can usually be broken down into sections eg in a guitar amplifier.. a pre amplifier section, a power amplifier section, a power supply and sometimes effects like tremolo or reverb.
In your example a 9 volt battery could be connected between +'ve and ground or a power supply could be built using a transformer, diodes and capacitors. The "input" in this case would be the ac into the transformer and the output would be the rectified DC smoothed by a capacitor.
Obviously no jack would be drawn at the input although a DC socket could be drawn at the output.
Ic's are great building blocks and easy to make work using only a few extra components.
In National Semiconductors data sheet they show the equivalent schematic of the chip which contains 10 transistors. It would be a lot harder to build that way and more expensive.
The ground connection symbol makes for a much more legible diagram than having them all connected together.
Hope it works out for you.