Difficulty understanding a circuits flow

[jdmmade]

Hello everyone, I am really new to electronics and have been reading Electronics for dummies, and am readying myself to move on to something a bit more sophisticated. Something that has been hard for me understanding is circuits that don't seem to have a start or an end. I do quickly understand the flow of a circuit if the battery is shown in the circuit and connected. For example, I cannot understand where this starts an ends, and why is configured the way it is. I plan to major in electronics, but I want to make sure I get the raw fundamentals of it, before I even attempt to make a simple sound amplifier. I would also like to ask. Where I could learn about multi meters and where I need to place probes, in order to find proper current, resistance through out a circuit, and voltage drops and what not?

 

[vk6kro]

[PLAIN]http://dl.dropbox.com/u/4222062/opto%20coupler.PNG

The power supplies could be shown as above. They don't have to be batteries.
It is less messy to just show +12 V where it is apparent that the other end of the power supply is the negative side of the battery and is connected to the bottom grounded part of the circuit.
It is not something to get worried about.

The semicircle device at the bottom left is an integrated circuit and it could be one of many types.
The important thing to know is that the output is either 5 volts or zero volts relative to the negative side of the battery.
If it is 5 volts, no current flows in the LED part of the optocoupler. If it is zero volts, current does flow in the LED.

The circuit takes a low powered output from an integrated circuit, isolates it in an optocoupler and uses a transistor to switch a motor on or off. Pretty good trick.

We can talk about multimeters later if you like.

 

[jdmmade]

The power supplies could be shown as above. They don't have to be batteries.
It is less messy to just show +12 V where it is apparent that the other end of the power supply is the negative side of the battery and is connected to the bottom grounded part of the circuit.
It is not something to get worried about.

The semicircle device at the bottom left is an integrated circuit and it could be one of many types.
The important thing to know is that the output is either 5 volts or zero volts relative to the negative side of the battery.
If it is 5 volts, no current flows in the LED part of the optocoupler. If it is zero volts, current does flow in the LED.

The circuit takes a low powered output from an integrated circuit, isolates it in an optocoupler and uses a transistor to switch a motor on or off. Pretty good trick.

We can talk about multimeters later if you like.

Thanks so much! I really appreciate your explanations, I am trying my hardest to begin designing and building my own analog synthesizers and such. This is a passion. I recently bought three other books that were higher rated then the average electronics learning books. Heres the list. "Getting Started in Electronics - Forrest M. Mims III", "Timer, Op Amp, and Optoelectronic Circuits & Projects - Forrest M. Mims III", and Electronic Formulas, Symbols & Circuits - Forrest M. Mims III". If you know of any books that are purchase worthy, please let me know.