Posts Tagged ‘electronic’

The Making of Dojikko

Sunday, August 24th, 2014

A look at how the clumsy autonomous robot was made, and her very first versions, when she was worse than clumsy, before she was even slightly clever. There’s more to show, but it was already approaching my longest ever video, so I decided to end it here.

[Watch in HD]

A later version can be seen here. She’s progressed a little further still, now – I should upload a video of her outside soon!

Music by Kevin MacLeod (

  • “The Way Out”
  • “Dance Monster”

DIY Printer P1: Basic concepts & smoothly moving the motors

Sunday, July 6th, 2014

The first in a series of “making of” videos where I make a super-basic printer controlled by an Arduino! I recorded pretty much every step of the way, so you should hopefully be able to follow the progress from pretty much nothing (here) to something that actually works.

[Watch in HD]

I started this project almost a year ago, but I’m only uploading the videos now that I’m sure it actually gets somewhere and that I didn’t just abandon it like I do with most of my projects.

The rest of the videos probably won’t feature so much editing work – I just needed to do that in this video due to my explanations that would be too hard to follow if I just kept my speech and video of my hand moving enthusiastically in front of the camera.

I should’ve made a compilation of every time I said “Basically” at the end, basically.

Dot Matrix Print Head in Slow-Motion

Sunday, June 29th, 2014

I got a second-hand, old-style dot matrix printer whose print head that needed cleaning, so I decided to quickly record this while it was out of the printer.

I’d love to see this with a proper high-speed camera.

[Watch in HD]

Replacing capacitors in 40-year-old headphones

Wednesday, April 16th, 2014

Or: How not to solder / How to annoy people by saying “can” as many times as possible.

These Superex Pro-B VI studio headphones from the 1970s belong to my grandpa, and sound amazing, but only when they work. Which, unfortunately, was not very often. I looked around online, and it’s apparently fairly common for the capacitors to die with age. So I replaced each (0.0025 uF) with the closest value I could get hold of (0.0022 uF).

[Watch in HD]

Let-down noticed after a few hours: It didn’t fix the problem. But at least that’s two components that should last longer now. But if it’s not the capacitors then it may well be the custom-wound transformers in each ear, which are obviously not made anymore. Oh well, it gave me an excuse to make a casual camcorder/chatty video for the first time in a while.

Dojikko Weight-Carrying Test

Thursday, June 13th, 2013

I decided to see how much weight Dojikko, my work-in-progress robot, could comfortably carry. I cut out 3 boring tests and yet it’s still kind of boring.

[Watch in HD]

Dojikko on a 9V battery (or two) (2013-03-28)

Thursday, May 16th, 2013

She drains them in minutes. They were cheap, though. Her usual battery is an 11.1V 5000mAh LiPo.

[Watch in HD]

Dojikko vs a corner (2013-03-18)

Thursday, May 2nd, 2013

Ultrasound fails when it comes to corners. It gets reflected away by the walls and the walls become invisible to it.

[Watch in HD]

[Dojikko] Turning bug (2013-03-03)

Thursday, May 2nd, 2013

The code was supposed to prevent constantly overshooting while turning to face a new direction, but it had quite a different effect. This is the kind of weirdness that happens on the very first attempt of adding new code.

[Watch in HD]

It was fixed shortly after recording this. =)

Ultrasound and Slow-Motion Recordings of Dojikko

Sunday, April 14th, 2013

The ultrasonic pulses that let Dojikko “see” her surroundings are normally inaudible to humans, but now, you can hear in detail exactly what’s going on. The ultrasound is 40 KHz, about double the highest frequency that most people can hear. When slowed down, not only can you hear the transmitted pulses, but the echoes and the delay between them are clearly audible, too!

[Watch in HD]

I recorded the sound at a very high sample rate (192 kHz – at this rate, the microphones can hear frequencies up to 96 KHz). Afterwards, I slowed down the sound to a quarter of the original speed, 1/8th, 1/16th, etc, even down to 1/128th (at that speed, just 2 seconds would be over 4 minutes long). I also recorded video in slow-motion, but my camcorder can only go up to 200 FPS (1/8th speed when played back at the usual 25 FPS), meaning that lower speeds such as 1/64th aren’t smooth, as I had to futher slow down the video in editing. But the main point of this video is the sound.

[Dojikko] Amusing bug – First test of closed-loop system for moving forwards

Thursday, March 28th, 2013

I tried to implement a closed-loop system to keep the actual speed the same by increasing power to the motors if e.g. stuck on an object. Results were… amusing.

[Watch in HD]

The speed was correctly being calculated from readings from the ultrasonic rangefinder. There turned out to be a combination of 2 problems (a variable overflowing, and something specific to the format of data that the Sabertooth motor speed controller requires), but they’re fixed and it’s working much better now. I’m still fine-tuning it, as it’s still far from ideal, though (either slow to respond or over-aggressive and dangerous, and interferes with other systems such as the part that detects if it’s stuck).