(Note: Due to changes in iOS – this app is no longer available… sorry!)

I shipped a new iPhone app a few weeks ago – “Resistor Photo ID”

It uses your iPhone’s camera to help identify resistor values.

(check out my other iPhone apps here)

I specifically developed it with color blind people (like myself) in mind – who can’t successfully ID resistors even if they take the time to learn the color codes.

Click here to get it from the Apple App Store (currently free!).


Using resistor ID is easy:

1. Take a photo of a 4-band resistor using the app

2. Drag the numbered bars over the corresponding resistor bands

3. Resistor Photo ID provides you with the resistance and tolerance of the resistor!

If for any reason Resistor Photo ID doesn’t detect the correct color for a band – you can easily override it.

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11 thoughts on “Resistor Photo ID

  1. Wow! This is such a great idea! I have a hard time with resistors, too, mostly due to color blindness but also with the small sizes and getting older. I played around with it with the CAPTCHA on the Adafruit blog, which is where I read about it. Hope you won't mind a few suggestions:

    1. Seems like adding support for 5-stripe resistors wouldn't be too difficult. I've not come across one in real life, so it doesn't affect me personally. Just a thought.

    2. You could add a little "AI" or sanity checking on values. For instance, the app read the first stripe as Black in one case. I don't think that's possible. Probably if it looks black in that case, it's brown. There were a couple of black/brown misses, but some of that may be due to the fact that I was taking pictures of an image of a pretend resistor on a computer screen.

    3. To expand on the above concept, there is a well known series of extremely likely values, esp. in the context on a given tolerance. Your app could hypothetically take this into account when deciding what color a band is. If trying to decide whether a resistor is 47 or 57 ohms, well, it's very likely 47. Probably more work than you'd want, but it could make it into the "killer resistor photo id" app 🙂

    4. A couple of times when going to take a photo, the shutter leaves didn't open. Not sure what was going on there.

    5. Most of all, *thank you* for a great idea brought to fruition! Kudos!

  2. I have wanted something like this for a long time. Any chance you would make it for an android? I would be willing to pay a reasonable price for the Android app.

  3. haven't dipped my toes into doing android stuff yet – so I'm not planning on doing a version any time soon.

    but – I'm certainly not claiming any "rights" to the idea – so if any android devs want to make a clone – go for it!

  4. Seconded as well, as I have a 'Droid here.
    On the flip side, can someone do one of these for those nasty little SMD resistors? A lot of folks spot recycle these from dead boards and the 0603 are not human readable.
    Capacitors are sometimes UV marked with little dots so aren't easily ID'd.

  5. Am aflat aceasta pagina, dupa ce am cautat despre Resistor
    Photo ID | Nothing Labs pe Google. Se pare ca informatia dvs e foarte valoroasa,
    mai ales ca am mai gasit aici si despre ora, ora exacta,
    lucruri interesante si folositoare. Mult succes in continuare!

  6. Why is this app not available in the Canadian store. I do a great deal of custom electronic amplifier builds. Being color blind I am forced to check every resistor with a meter. This app would be a great help by saving me a lot of time.

    1. Unfortunately due to some changes in iOS – this app is no longer available (in all App Stores for all countries).

      All the best,


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