Apologies for the remedial post, but how do I tell resistor from resistor? I know that the bands represent a coding, but in which direction, or does direction matter for calculating the value?
Most resistors have a gold or silver band for the tolerance, and that's always on the right. If there's no tolerance band, then the other three will be at the left.
Edit: Google "resistor colour code" or similar, and you'll get loads of pix.
Ah, I had the decoder from imge search but the gold/silver orientation was my missing link. Thanks much!
Sometimes the tolerance band is brown, and the way to tell it apart
then is the slightly larger gap between it and the others. If the resistor is one of
the cyan coloured ones its hard to tell red from brown sometimes, and a
multimeter is useful to have at hand to double check.
Indeed, the tolerance band can be any colour, in which case yes you kinda hope there's a bigger gap on the right hand side, sometimes difficult to see on small parts. Best to hope for silver and gold though!
And yes, a meter is indispensable, so @blah44 you best get one if not already!
20% resistors, I don't think are even made any more.
For 2% and higher tolerance, you'll see 5 bands, four for resistance plus the tolerance band.
Note the gap separating the tolerance band. That gap is not always present in 5% (gold) and 10% (silver) four-band resistors.
I use mini resistors. Panasonic used a pale aqua color for 1% resistors that made it fairly easy to see the color differences, but the striping was so inconsistent (fading, placement, thickness) that it got hard to tell which end was which when the value started with a brown stripe. When those went end-of-production, I switched to Stackpole. They use a deeper blue that makes white, gray, and yellow tough to tell apart, likewise with red/orange/brown.
Of course, with their size (a little bigger than those glass small-signal diodes) reading the bands can be challenging anyway. They're all close together, so the "more space before the tolerance band" rule goes right out the window. But man can you pack those things onto a PCB!
Keep your inventory well organized, and always check with a meter if there's any doubt.
With surface mount resistors they print the codes as text (but alas carefully arrange
that 2, 5 and often 1 are completely symmetric so you have to get the tweezer-multimeter out!
More confusingly they print the multiplier as a digit, rather than use engineering notation.
Half the capacitor manufacturers are scared of nano- and milli- prefixes, one does wonder
how component value labelling got that way.