Resistors - metal film or carbon film and what values?
(1) Use metal film where possible. Fewer bad surprises. At 1 cents each either way the cost of bad surprises exceeds the component cost, even if the cost is only measured in frustration and wasted effort.
(2) Wouter (correctly (of course)) says "evenly spaced" but doesn't quite explain it. He means that the ratio between adjacent resistors should be about the same. You should aim to always include the powers of 10 values and then have as many as appropriate in between to fill in.
SO
1, 10, 100, 1000, 10000 ...
OK, that one was obvious.
But sqrt(10 ) = 3.16, so
- 3.16, 10, 31.6, 100, 316 ... :-)
BUT they don't make 3.16 etc in sensible standard ranges, so using the nearest "E12" values:
1, 3.3, 10, 33, 100, 330, 1000, 3k3, 10k, 33k ...
The "obvious" thing to do may be to use
1, 4.7, 10, 47, 100, 470 etc
BUT the ratio of 47/10 = 47 (of course) BUT the ratio of 100/47 = 2.13.
So, if you had a fixed voltage and were connecting successively higher value resistors to ground the change from 100 to 470 would decrease the current by a factor of 4.7, but the next step from 470 to 1000 would reduce the current by a ratio of 2.13. As you went up the currents would change by factors of 4.7, 2.13, 4.7, 2.13, 4.7 ...
You usually get more than 2 steps per decade.
The smallest sensible number has 12 steps per decade.
These are say 1, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2, 10 ...
If looked at by resistance difference the series seems uneven, The differences are.
0.2, 0.3, 0.3, 0.4, 0.5, ... 1.4, 1.8
BUT - when looked geometrically by ratio we see:
1.2/1 = 1.2
1.5/1.2 = 1.25
1.8/1.5 = 1.2
2.2/1.8 = 1.222
2.7/2.2 = 1.227
3.3/2.7 = 1.222
...
10/8.2 = 1.22
SO, within the resolution afforded by 2 significant digit numbers we see that the ratio of adjacent resistances is about 1.21152766 :-) .
I use that "strange" value as it is the twelfth root of 10. If you multiply a number by 1.21152766 twelve times you get a result 10 times larger.
So if you space twelve resistors across a decade range with each a factor of 10^(1/12) larger than the prior one you get resistors which increase in value "smoothly" from a current flow point of view.
E12 - 12 resistors per decade spaced in value by a ratio of the 12th root of 10 .
E24 - 24 resistors per decade spaced in value by a ratio of the 24th root of 10 .
E48 - 48 resistors per decade spaced in value by a ratio of the 48th root of 10 .
E96 ...
More anon maybe .... brake pads to change, darkness fallen ...
If you are going to be doing a lot of analog electronics, you should buy metal film. Metal film produces less thermal noise than carbon. Metal film resistors also typically have a much lower inductance/capacitance than carbon so they(metal film) work better at higher frequencies. Carbon has no real advantage except that they are cheaper. If I was only going to work on digital stuff, I would buy the carbon comp.
As far as what values, the values you have chosen are reasonable for digital stuff. If you think you may use op amps or transistors to amplify the signal, I would look into the E6 series of resistors.
(1) Go for metal film resistors. Typically, they are of 1% precision, compared to 5% precision for the carbon film ones. Also, their values vary less with temperature changes.
(2) For initial stockpiling, I'd suggest purchasing a broader set of values. Otherwise you risk making frequent trips to the local store, just for a pair of resistors, for the next cool project you found online. At 2AM on a Sunday, it spoils all the fun.
Here's a sample set of 25 values, from the E6 series:
100 150 220 330 470 680
1k 1.5k 2.2k 3.3k 4.7k 6.8k
10k 15k 22k 33k 47k 68k
100k 150k 220k 330k 470k 680k
1M
(You may want to add the 10 ohm ~ 68 ohm ones as well)
These can be further combined, to substitute for other values. Wolfram Alpha is my preferred calculator and there are many others online. For example: 314 ohm