Finding rotation speed using Arduino

Ooops, it’s been a while since I was last active here, sorry about that.

But to offer someting in retribution, here’s a device that can count revolutions or any other event that closes a switch, and tell you how many times that happens in a minute.

I have a need for this device, because I am building a dolly for timelapse images. The dolly has a 2m long worm screw that makes the dolly travel along an axis. If the trip takes, say, 3 hours, and the dolly carries a camera that is set to take an image every 5 seconds, we get a 3 x 60 x 20 image timelapse, ie. 4,800 images. With 25 images per second in a video, that gives you a 192 seconds, or, a little over 3 minute time lapse. During which the camera moves, you see, it’s not just a timelapse.


Accelerometer, that tiny workhorse

The accelerometer chip (1 x 1 cm)

The accelerometer chip (1 x 1 cm)

Accelerometers are wondrous little devices that offer boundless possibilities… as soon as you figure out a need for them.

For some time now, I have been thinking about a filament break detector for 3D printing. Filament comes in spools of 400m (1 kilogram) and they are usually hung on racks on which they rotate. The filament is fed to the printer via a small stepper motor turning a grooved feed wheel. If the filament breaks, or the feed wheel eats a notch into the filament, it will no longer enter the extruder, and the print fails. Usually the filament wire breaks if it has been exposed to air humidity for a long period – it is hygroscopic and becomes brittle.

The printers are not aware of the filament feed. There is no detector for smooth feed, and consequently any hitch in feed will fail the print. I have thought of making an optoelectronic feed detector that would shine a light on the filament spool and detect its movement, but that would require a striped disc to be attached to the spool, as well as the actual reading device installed on the rack. Then I thought of a mechanical device that would ride on the filament itself and detect its movement via rotating discs, but that soon turned out to be too complex. (more…)

Proof of concept: servo speed and rotation

Hi again!

As I was kindly invited to Porvoo to speak at the Point College Internet of Things day, I thought I’d finally formalize a concept I have been thinking about for a while now: servo rotation direction and speed controlled by a potentiometer.

This little combo is not much on its own of course, but as it happens, it can be used for a multitude of things. To get us started with servos and potentiometers, see this two axis camera stand: (more…)

Building a 2 way tiltable webcam stand

Hi again.

This time I thought I’d write up a little device I have put together with Arduino and printed parts so that I can point a webcam in two directions. (That’s the first use I thought of, after getting the idea of trying something with two 180° servos). To achieve this, I bought two potentiometers (adjustable resistors) and set up two servos to rotate the stand.

Here’s a little video of it in operation: