You may have seen surveyors (or maths students) running around with measuring wheels, counting the clicks to measure distances. [AGBarber]’s digital measuring wheel works in much the same way, but with the convenience of a measurement you can read off a screen.
The design is simple, and relies on the outer wheel of the device turning a mouse encoder wheel. This is read by anArduino Pro Mini which runs the show and records the requisite measurements. It then drives an SSD1306 OLED display which shows the measurements to the user. It’s all wrapped up in a 3D printed housing that makes it easy to roll around the small handheld device.
The wheel’s maximum measuring length is 9999.99 cm, or just under 100 meters. Given the size of the device, that’s probably more than enough, but you could always build a bigger version if you wanted to measure longer distances.
Measuring wheels make it easy to measure along curves, and are just generally fun to play with as well. You could certainly use one to determine whether flat tyres are making your speedometer lie to you. Or, you could dive into this great talk on measurement from [Adam Savage].
https://youtube.com/watch?v=iSWSXXlQFeU%3Ffeature%3Doembed%26autoplay%3D1
Kinda small for measuring real estate, doncha think?
I wonder if you could make one without moving parts, just an IMU, and rotate the entire thing?
Sure, that doesn’t seem very difficult either, but wouldn’t that have exactly one moving part? You’d want it to rotate very smoothly (so, use bearings) to prevent slipping of the wheel on whatever surface it’s rolling on.
Yeah, I suppose it would technically be dozens of moving parts counting ball bearings and switches and the battery or usb connections.
Lasers anyone? And where’s the handle for long ground/floor measurements? What about measuring water distances (not enough friction)? Use GPS RTK for “impossible” measurements like forests, rocky flats, etc. I like the way all the bearings fell out. But still, it really is a good build.
If it isn’t measuring anything, I find this to be a fidget I want in my collection :)
When I lived in Japan in the mid-late 70s all sorts of crazy and interesting calculators abounded at the electronics shops in Akihabara which I loved to frequent. One of them I recall was a ruler with a calculator in it, nd at one end a small metal wheel, 10 or 15mm diameter or so. It would be rolled around a picture or map or whatever and give the distance.
i thought it pretty cool at the time, I recall there was little to no discernible resistance when twiddling the wheel.
They are still around and called curvimeter or “map measurer”. We had an analogue curvimeter and used it to track the route on the map with the little wheel to see how far it was to our destination
Silicon Chip magazine published a DIY design for a map measurer in the early 1990s. It used a calculator for the smarts, and a round “servo horn” from an RC servo, drilled to pass light from an LED, one pulse of light per cm rotated by the servo horn. A phototransistor triggered the “=” button on the calculator. Most calculators of the era had a “continuous add” feature, where if you pressed the “+” button twice, it would repeatedly add to the total every time the “=” button was pressed afterwards.
So, to use this gizmo, you soldered a pair of wires to the “=” button on your calculator. Then you pressed “1++” on the calculator, then you rolled the servo horn over the route on your paper map. The count on the screen would increment by 1 for every cm on the map. To calculate distance, you would subtract 1 from the total, then multiply by the scale of the map. Simple:-)
Unfortunately I can’t find the article on their website – they haven’t digitised all their old issues yet. It’s either that, or I’m using the wrong search terms :-)
Project: Map Reader For Trip Calculations by Malcolm Young & Leo Simpson, p64, March 1989. https://www.siliconchip.com.au/Issue/1989/March/Map+Reader+For+Trip+Calculations
That’s the one, thanks Tim. I was searching for “map measure” without success.