# Unknown Spec LED Resistor Finder #2 (with Switches)

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## Introduction: Unknown Spec LED Resistor Finder #2 (with Switches)

Same as my other resistor array breadboard but you don't move the LED around. Just push the buttons! Also useful for changing the resistance in various circuits.

## Step 1:

The higher up you push the lower the ohms and the brighter your LED shines!

## Step 2:

Bend and snip. I bend my resistor legs over a the square hinge on some small pliers.

Ready.

## Step 4:

Save the ends of the resistors for jumpers.

## Step 5:

Get a bunch of switches.

## Step 6:

Put them in the board with the jumpers. I am not paying attention to rail polarity here. You can if you want but this keeps wiring neat.

## Step 7:

Line up your resistors by value. 5 band resistors can read both ways so be cautious and check your reads with a meter. Left to right and right to left reads can be totally different.

## Step 8:

Put them in the board. Note that they are staggered left and right. Lowest values are at the top and increase as you get closer to the bottom of the board.

## Step 9:

You'll end up with the jumpers to the inner rail and the resistors to the outer rail. All these switches are now in series with the resistors and in parallel with each other. Wire a LED in series with the rails and start pushing buttons from the bottom up. When your LED lights up nice and doesn't blow up you have found the proper resistor to run it!

## Step 10:

Wire the other side in as well. The way these are wired the closer to the LED the switch is the higher the ohms. This board has continuous rails but some are split in the middle. Keep that in mind if you build this. Also note if you press TWO or more buttons you will end up with a parallel resistor circuit. So like 1/Rt = 1/R1 + 1/R2 + 1/R3 yadda yadda yadda... press two buttons at your own risk.

## Step 11:

That is all. When something works use it. I wrote the values of these resistors in order on the back of the board. These go from 2.2 ohms on the top of the array to 2.7 kilo-ohms at the base of the array but use what you got. I have dozens of each so when I find what works I go to my part bin and grab the same. This is good for LEDs that you have no info on and stuff you salvage. LED resistance calculators are great but if you have no values to punch in they aren't much use. This is pretty safe to 9 volts but expand the array to higher ohms if you use higher voltages. Check my other resistor array for more detail on this idea and a version that does not use switches. I hope you find this useful.

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## 6 Comments

A four dollar board (that I already have) 67 cents of switches and 25 cents worth of resistors is expensive?

4 replies

67 cents for 25 switches ? No, 2.5 euro at RS, but I admit I thought it was more expensive. Two rotating switches, one for hundreds the other for decades is more elegant, cheaper and more efficient, but that's only my opinion.

Try banggood.com you can get 100 of these switches for just over two canadian dollars with free shipping. Shipping is slow but it makes hobby work cheap.

Good to know.

Yes cheap and useful. I got my parts from banggood.com slow shipping but reliable and shipping is free.

A bit expensive for a gadget. But if one really want this, a rotating switch is cheaper.