This is the schematic I'm looking at:
http://www.555-timer-circuits.com/toy-organ.html

I'm very new to electronics and the circuit diagrams still look very daunting to me. When it says "100n" next to a capacitor, is that just an abbreviation for 100nF? On that schematic, there is also something that says "10u" next to an electrolytic capacitor. What does that mean? Is that supposed to stand for 10μF? Also, if there was no sign next to a capacitor in a schematic and just said "100" should I assume it means 100μF? And in resistors, if it just had a number, should I also assume that it means 100Ω? In that schematic there was also a "8R Speaker". What does R stand for? I heard that it meant 8Ω Speaker, but I don't understand how resistance has anything to do with Speakers.

Another unrelated question: I bought a pack of PNP transistors at Radio Shack. I know that transistors amplify current, but how do you know by how much? Do all transistors amplify the same amount of current? Are all of my transistors in that pack the same?

Thanks so much for the help, I'm still a nube and I appreciate your time!

Christian

 

yes
yes
yes
yes
R stands for ohms
Speakers have impedance, measured in ohms
transistors have a rated current gain beta or hFE which is listed in the specs
no
no

 

Schematics tend to use a lot of short-hand notations, many of them stemming from the days when they all had to be hand drawn and/or when typesetting had limited character sets.

Component values frequently omit the base unit {Ω,F,H}. Despite my obsession with units, I'm willing to buy off on this one because the symbol associated with the base unit suffices. None-the-less, there isn't any reason not to include the base unit these days, unless your schematic capture package, whatever it is, doesn't support it (most likely the Ω symbol).

Replacing 'µ' with 'u' is very common. In fact, that is still used a lot today when using a text editor. It virtually never causes any confusion. Other notations, particularly on older schematics, that you will see will be 10mmF, which is 10 milli-millifarads, or 10uF. You may also see 10uuF, which is the same as 10pF.

A common convention, particularly with caps, is to have a default unit that is to be assumed unless otherwise specified. For caps, this is usually uF, although occasionally it will be pF. It depends on the type of circuit. Usually, somewhere it will say what the assumed unit is, however that statement might be on page 3 of a book containing dozens of schematics and you are only seeing what was on page 17. In your schematics, put such information on each schematic page.

The '8R' comes from a convention that has largely disappeared, but was actually a very useful convention. Imagine a paper schematic that had an 8.2k (Ω) resistor, but the schematic is old, stained, and crinkled. That little period gets hard to distinguish from all the other little spots. Similarly, is that a period or just a tiny burn spot from a spark making that 47u look like 4.7u?

So the convention developed of having the multiplier serve as the decimal point, as well. So 8.2k would be shown as 8k2 while 47u would be 47uF but 4u7 would be 4.7uF. But what about if there isn't a multiplier (something that seldom happens with caps or inductors)? Well, just use R (they probably would have used Ω if it were practical). So 4R7 is a 4.7Ω resistor while 47R is a 47Ω resistor. A schematic using this convention of indicating the decimal point will (should) use it for ALL values, otherwhise is that really 47 or is it 4.7?

As my eyesight gets worse, I find myself wishing that schematic capture software today still used (or allowed) that convention. I have a hard time reading the digits, let along determining whether there is a damn decimal point.

Another unrelated question: I bought a pack of PNP transistors at Radio Shack. I know that transistors amplify current, but how do you know by how much? Do all transistors amplify the same amount of current?

As Mr. Chips said, the transistor will have a parameter, called either hfe (the 'fe' is supposed to be a subscript) or ß (beta) that is the forward current gain that relates the base current to the collector current. Just like other components, transistors come in all shapes and sizes with widely varying parameters. You need to look at the data sheet for the particular transistor to see what it's beta is. Be forewarned, even transistors that are supposed to be identical will have different betas (but should be reasonably close) and a given transistor's beta will vary considerably (and I do mean considerably) under various conditions. The data sheet will give you a feel for how much variation you can expect. But, because of this variability, most decent circuits are designed so that the exact value of beta doesn't really matter, just that it be above some minimum value and, occasionally, not more than some maximum value.

Are all of my transistors in that pack the same?

Probably, unless it is a 'variety pack' or an 'assortment'? And, even if they are, they are only nominally the same, each one will be somewhat different than the others.

 

Note the different styles between MBahn's responses and mine. Different strokes for different folks.

 

The terse versus the verbose.

 

Or is it the verse and the terbose?