This is a small resistor array I made so I can figure out what resistor to use with various LEDs at different voltages. They start at 2.2 ohms (at the top) and go up to 2.7 kilo-ohms (at the bottom) .Plug the LED in across the board and work your way up till you see a usable brightness for whatever you happen to be doing. For a group of LEDs you can arrange them at the base of the board and use jumper wires to probe the different resistors. You can see the different brightness of these two LEDs at different points on the array. If I try any lower resistance values I would probably end up destroying them. You don't test two points on the board at a time. This is just so you can see how they vary their output. These are all resistors that I have on hand so when I find what works I just grab another out of my parts pile. Not shown here is that I wrote all the values on the back of this breadboard in the order they are on the board. So here the 16th one down the board is very bright. On the back of the board I can see I have written that the 16th resistor is 82 ohms. Way too bright for an indicator light with 9 volts but suitable for a flashlight or toy.
Step 1: Bend
Bend your LEDs over something appropriate and snip off the legs. I use a small pair of pliers.
Step 2: Bent
Step 3: Build the Array
The jumpers are the leftover resistor leg cut offs. Five band resistors are a real pain to read. If you read them left to right or right to left you can end up with two different values. Always check these stupid things with a meter even if you think you know what they are. Doesn't help that the colors are pretty close in shade to each other too. Is it yellow? orange? silver? grey? It's enough to drive a guy crazy. But for a few dollars I got a bunch of values so I can't complain too much. Also note that I skip every fifth row on the resistor side... which works out pretty good since my resistors are too big to line up row for row and the rail on the right skips one every five anyway.
Step 4: Plug in Your Power
Here I am using 9 volts but plug in whatever suits your needs. This particular breadboard has continuous + and - rails on the sides of the board but some are split. Keep that in mind if you use more than the first half of the board. If you use more voltage you will also probably have to add higher resistor values. With a little poking you can find a resistor that lights up your LED an acceptable amount. Handy for salvaged LEDs or ones that you have no info on. LED calculators are great but if you don't have values to plug into them they are kinda useless. I hope you find this useful.
Peterthinking made it!