What is it?

Ohm Parade is a programmable resistor: it can act like any resistor between 10Ω and 2.56KΩ, in 10Ω steps. It's like a mini decade resistance box that fits on your breadboard for easy tinkering! Resistance is adjusted with a set of 8 DIP switches - add up the resistor values you need and flip the switches accordingly. Or if you're a math wizard, convert (your resistance / 10) to binary to get your switch settings. You can plug either end into your breadboard, or even use alligator clips on the exposed pads on either side. It's available as a kit (THT components only, so it's a good starter to learn basic soldering skills), or fully assembled.

Note: This is a hobbyist tool, not a precision instrument, and should not be used in critical situations or outside max component ratings of 100mA / 1/2W. Accuracy should be approximately +/- 1% under most normal conditions.*

Wait, how do I use it?

OK, there are two ways to think about it. Let's say we want an 870 ohm resistance. Look closely at the numbers under the DIP switches: 10, 20, 40, 80, 160, 320, 640, 1.3K. One way is to simply figure out which combination of these add up to 870: 640 + 160 + 40 + 20 + 10. (it's easiest to start with the biggest numbers and work your way down). Then just flip those switches ON (up) and the others OFF (down) to get 870 ohms across the header pins.

The other way to do it, which is easier if you have Google at hand or are good at mental binary math: Take your resistance (870), divide by 10 (870 / 10 = 87), then convert to binary (87 = 0b01010111) - this binary number represents the correct switch settings!* (where 0 = off, 1 = on - see the last product image above for visual explanation)

For safety, it's best to flip the main cutoff switch (on the left side) to OFF before adjusting the DIP switches - this way, you're not adjusting a live circuit and it's harder to accidentally set too low a resistance and burn up your circuit. Confirm your DIP settings look good, then turn the main switch back on!

Why did you make it?

Ever needed a particular resistor and find you're fresh out? Or experimented with an LED to find the right resistance to get that perfect level of brightness? Sometimes fiddling with all those taped-together resistors and trying to remember your color codes when you find a "loosie" is just a pain. Keep an Ohm Parade in your toolbox and save yourself the trouble.

What makes it special?

Well, it's cute as a button for starters. It's made to be unobtrusive on a breadboard and handy to keep around. Unlike some resistance boxes which use large banks of jumpers, this one uses only 8 switches and the magic of binary addition.

Hmm, I’ve never seen a 640 ohm resistor...

Some of the resistances are made by adding up multiple resistors in series (10 + 10 = 20) or parallel (680 || 11k =~ 640).

What’s with the asterisk*?

Sharp-eyed customers will note that while the “correct” largest binary resistor would be 1.28K, we use a 1.3K resistor. If using the binary conversion method above, subtract 20 from your desired resistance if it’s >1.28K for maximum accuracy.