A Fancy Connected Caliper For Not A Lot

An essential for the engineer is a decent caliper, to measure dimensions with reasonable accuracy. Some of us have old-fashioned Vernier scales, while many up-to-date versions are electronic. When entering large numbers of dimensions into a CAD package matters can become a little tedious, so the fancier versions have connectivity for automatic reading transfer. [Mew463] didn’t want to shell out the cash for one of those, so modified a cheaper caliper with an ESP32-C3 microcontroller to provide a Bluetooth interface.

Many cheaper calipers have a handy hidden serial port, and it’s to this interface the mod is connected via a simple level shifter. The ESP and associated circuitry is mounted on a custom PCB on the back of the caliper body, with a very neatly designed case also holding a small Li-Po cell. It adds a little bulk to the instrument, but not enough to render it unusable. Whether the work required to design and build it is worth the cost saving over an off-the-shelf connected caliper is left to the reader to decide.

We’ve covered similar hacks in the past, but this one’s to a very high standard. Meanwhile if calipers are of interest to you then they’re a subject we’ve examined in some significant detail.

18 thoughts on “A Fancy Connected Caliper For Not A Lot

  1. With a LiPo and battery monitor it should be a good deal less irritating than the usual habit of cheap calipers of draining the batteries (a button marked “off” – someone has a sick sense of humour!)

    1. That’s why it’s worth getting the less-cheap ones.
      Is a video of Clough42 showing genuine Mitutoyo use 14x less battery than the cheap ones (even cheap ones dressed up to look like Mitutoyo)
      I bought my Mitutoyo from Amazon for £87 and they appear to be genuine. That’s 4x the price of cheap ones (ignoring the really cheap 0.1mm resolution ones) but 2 years later they are still working with the original battery, so offer 4z the availability.

  2. Nice.
    I had my caliper(s?) confiscated last week by airport security. Rightly so, I guess – the spike could be fairly lethal.
    Anyway. In this project the ESP32 mimics a blekeyboard to send measurements. I like the simplicity…but…
    Tangential, but perhaps a good forum to ask:
    1. Is there an open protocol to send measurement data like this project produces?
    2. Is there some app/software than accepts is and can graph it etc?

      1. Yeah, I was more thinking about language than the protocol I guess (or maybe both).
        I long while ago I did get an ESP32 talking to Arduino (prev Google) Science Journal App
        But never got round to working out how to create new device on ESP32 side. Wasn’t straight forward (hence my admiration of blekeyboard solution).
        From memory the ESP32 should tell the app its ‘a Caliper’ and give units of measurements and then you are off measuring and recording. Would be quite useful.

        1. Haha. They did ask me what I was using them(it?) for and saw security people internally fall asleep inside as soon as I started to explain.
          Maybe that what they are worried about – me getting on plane intercom & regaling on my caliper skills … and then we are in the middle of Indian Ocean.
          Radio silence, just snores.

      1. >>and then you get metal cutlery with your meal

        I haven’t seen metal cutlery on a plane in over a decade. What airlines are you flying with, and where? I’ve done Europe, Asia/Oceania, USA and haven’t seen a metal knife or fork since a Lufthansa flight from Denver to Munich back in 2008.

        And no, the Lufthansa flight didn’t get hijacked. Nor did any of the other flights where I was allowed to keep my shoes and water. Stupid security theatre. I wonder if anyone has done a study of how many person-years this nonsense has wasted over the last couple of decades.

        1. Haha.
          Guess you’ve been turning right into all those planes, not left.
          Metal cutlery, glass glasses and a toilet shared with the pilots, if you can be bothered to get out of bed.
          Am sure there is a conspiracy there somewhere – haven’t the imagination.
          #still_missing_my_callipers ;)

  3. You say it hasn’t added enough bulk to make it unusable but in my opinion it has, it will make it a pain trying to get measurements on quite a lot of objects, ideally you want there to be as little as possible that can get in the way.

    Also using the exact measurement that the calliper spits out isn’t always that useful anyway, you generally want to round it to the nearest whole number or add some clearance. With how this is implemented as a ble keyboard it means you still need to use your computer to select what measurement or where you want to type the number, all you actually save is typing in the number and the callipers are harder to use.

    1. Hi creator here:
      The PCB housing are the exact dimensions as the (black) housing on the caliper. The jaws of the caliper are still completely unobscured and because I have used these calipers, I can say that the thickness really does not affect anything just because it is the exact same footprint as the caliper itself.

      Yes you usually add some clearance, there is a button that lets you add clearance that’s why there are two buttons. It’s pretty cool that this is programmable so you can make it do whatever you want. You say the part about typing out the number for you like it’s a bad thing? Lol the whole point of this project was that you don’t have to type the numbers into CAD and it’s pretty useful.

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