Jan 12, 2012

Resistor board. (how-to store thousands of T/H resistors.)

Great for shipping, but a bit impractical to store this way. Especially after using in breadboarded prototypes.
Recently I purchased a bulk pack of through hole resistors. The pack included 50 parts of 50 values, 2500 total resistors. They are 1% 1/4W type and were packaged as 50 "strips" each labeled with the corresponding values. All in all the pack was good, especially for the price, however there was 1 unlabelled strip and two 33k sets. After some testing I discovered it was a 33k and a 330k.

List of values I had received.
Previously I had bought a bulk pack of 5000 0402 sized SMD resistors. these were packed as 100 pieces of 50 values and were individually bagged in hot wire sealed bags. Storing these was easy, simply move the resistors into small zip-lock bags and store these in a box. Not the most elegant solution, but it works and was very easy and cheap to implement. Now with a heap of 2500 resistors on my desk I had a few problems.

Problem #1:
50 strips of resistors takes up quite a decent amount of space. It doesn't bother me if I have to look through a few strips to find the correct value, but looking through 50 is a laborious task. sorting the resistors into decade sets helped with this. eg one pile 1R - 8R2, another set might be 1K - 9K2. This helped in finding a correctly valued resistor from a batch of 50. First locate the pile with your chosen value in it. then find your value.

Problem #2:
Having used some resistors in a breadboard design (the reason I bought a bulk pack in the first place) I found myself with a few loose resistors on my desk. Not wanting to toss them into a junk bin never to be seen again I decided to create a storage system. I had a few criteria in my head while trying to work out how to store long pointy but fragile objects. I thought about a fishing tackle box approach, but having 50 compartments would be costly and large. and resistors being small would most likely be able to shift from compartment to compartment if the box was tipped.

The list turned into labels.
Eventually I settled on an idea that I had first seen in dick smiths funway into electronics. A technique not used much with SMD IC's the use of foam. I have previously used Styrofoam for this task however eventually you end up with considerably large holes in your Styrofoam from all the poking. I had some old packing foam from some computer parts that was lying around. It was about A3 sized and 5cm thick in the middle with thicker edges. After some testing to make sure the resistors could be easily poked into the foam without bending their pins I set to work writing out labels for the values I had.

No 330R!! D':
The labels could be made on a computer however if I want to add another value down the line it'll be easy from me to just quickly write up a label and it won't look out of place. Next I had to position and fix the labels onto the board. Glue could be used, but to increase flexibility in the future I created some holes in the labels and used a resistor to pin down the label to the board. I think this creates a cool effect that adds something that you wouldn't get from a plain piece of foam with paper labels attached.

Easily fits 50+ resistors.
With all the labels attached it was time to check out how much room 50 resistors would take up on my new resistor board. as you can see there is plenty of room if I ever buy more pieces of values I currently have or if I buy different values. It is quite time consuming transplanting the resistors from the strips onto the board so I think I shall leave the bulk of the resistors on the strips and only use the board for sorting resistors as the come out of my breadboard.

Final design. I like it and it's light able to be stored against a wall etc.


  1. There are also developments on the way the airpax and resistors just as what you have here. The creators are building a sleek and a more durable ones for it to become more effective.

  2. This solution, while extremely efficient, is unsightly and easily worn out depending how much electronics you do, the 1k area is going to get worn out to point that the resisters simply fall out, while the 4.7k would probobly last for years. Perhaps this solution would work better if you made a wooden/plastic grid with foam inserts instead of one giant foam board, that way the foam for commonly used resistors could be swapped out when they get worn.