Three Battery/Cell Types

Last summer I tried my hand at building a drone. I learned a lot about drone battery use, and eventually settled on a 14.8V (4*3.7V), 4000mAh Lithium Polymer (LiPo) battery with a 10C rating

In my last job we occasionally would use the lead acid batteries you can get at most hardware stores. The standard size we used was 12V, 7Ah, C5 capacity.

I also often use CR2023 coin cell batteries that provide 3V and around .2 mAh. I’m not sure of the C rating.

LDR Lamp Proposal


For the next few weeks I’ll be working on a light fixture for Light and Interactivity.

My light is inspired by the personal experience of being in a long term long distance relationship.

My plan is to create two reading lights to go above the headboards of two separate beds. They will function in two or three ways (the third is undecided – needs further thought)

  1. As a standalone reading light, perhaps with an auto-off feature after an hour or so (I sometimes fall asleep with the reading light on)
  2. As a subtle presence device for long distance partners. Currently my thought is that by touching one of the fixtures, the connected light will gently pulse; just enough to let the other person know you’re thinking of them, but not so much to interfere with their reading. Perhaps a reach goal here would be to have a ‘hold’ function, where if both lights are being touched the pulse intensifies.
  3. (This is the one I’m not sure about yet) Sometimes after I fall asleep with the light on my partner will turn it off. I wish I could say vice-versa but she’s too conscientious to fall asleep with a light on. So maybe there’s something in giving control of the other light to each fixture. But that could raise a few different questions; of agency, of who’s job it is to turn the lights off, not to mention the technical difficulties.


I started throwing together concept sketches for what this lamp could look like. As of now I think a feasible option is a strip of LEDs in a square aluminium bar with one long side open. The LEDs face the open side, which has a thin layer of diffusion on it.

The ends of the bar could be capped with 3D printed caps, that could perhaps double as the housing for the electricals.

Light Observation Week 4

This wasn’t taken this week, but I’ve had the footage for a while and thought this was a good opportunity to do something with it.

The first thing that catches my eye in this timelapse is the vastly varying brightnesses as the clouds pass over the sun. It’s not something that we usually notice at normal speeds, but sped up it’s obvious.

Near the end, just before the sun dips out of sight, we can start to see the reddish tint that would become a beautiful orange sunset were it not for the clouds. This is most obvious on the bare brick wall on the left hand side of the image.

Once the sun disappears behind the clouds, the ambient light on everything immediately becomes blue, as the still-bright sky becomes the main, very diffuse source.

Lighting Observation Week 3

Very seldom do I leave the floor in time to witness the sun setting, which I lament greatly.

It’s interesting that the sky is still quite bright, yet the streetlamp is clearly a hotspot in the image.

I don’t think this is necessarily ‘Golden Hour,’ as the light is a little low for super romantic Hollywood scenes, yet it is still beautiful. The sky’s gradient transitions from pale blue above to a deep fiery red at the horizon.

Near the horizon, the orange/red/yellow (fiery colours) bleed through the trees, adding to the seemingly glowing effect.

Further up, the bottom of the clouds catch the redder light, and the top of the clouds seem bluer – closer to the colour of the sky. The reds create a lovely contrast to the clouds against the blue sky.

Light Observation Week 2

A street in New York on a raining night

There’s something really compelling about headlights gleaming on a wet road. Usually tarmac is so matte, but add a splash of rain and it becomes very reflective.

The shape of the reflection is interesting; from the angle of the viewer the original source of each reflection is stretched out vertically.

There is a lovely texture to the reflections; the tiny bumps scatter the light so that you can see general pools of brightness and colour, but no detail.

The photo above has blown out the highlights, but in reality the pools of light reflecting from the headlights have a beautiful gradient of brightness.

Aside from the reflections, which draw so much of my attention, I love the way the light rain catches the bright beams of the headlights. Here you can see it best in front of the yellow cab. Just like dust or fog, this light rain gives the beams of light definition, volume.

Here’s a photo of the other direction, with similar scattered, long reflections.

Candle in the Wind (Version 002)

I have updated the candle so that it looks a little bit more like a candle.

Although the assignment was to replicate the essence of a candle, not necessarily remake a candle in the literal sense, I decided to enclose my e-candle in a way that evokes the real deal. Since I’m going for the feeling of lighting and un-lighting a real flame, I figured a true-to-life look would help sell the experience.

When all you have is a hammer…

Last week I took my first DIP into ATTiny waters. Although using the ATTiny adds a tad more complexity into completing a project, it opens up many new possibilities for small enclosures.

Originally I didn’t intend to use the Tiny this week. I had procured a large candle to house the electricals, but like a muppet I drilled too fast into it and broke it in half.

A candle, broken in half.

I panic-raided the junk shelf to see if there was an appropriate container that I could melt the wax into or something, and found a single tealight candle. Not one to shy away from a challenge, I found myself asking: can I fit A into B?

Thus came about my second attempt with the ATTiny85

The Process

The process was simple enough, since I had everything breadboarded up. I first made sure the circuit worked on a Tiny, which it did without much trouble.

I had a blank PCB board that, with some adjustment, fit nicely into the candle’s cavity.

I got pretty tunnel-visioned during the soldering, so the only picture I have of the process is of these markings I made to help me identify the different sides and orientations of the chip…

Fortunately everything went well.

In the end the package just fits within the candle. The microphone sticks out a little but as the project currently stands that is unavoidable. Perhaps the next iteration of this project could involve a NeoPixel ring instead of the jewel, and house all the different sensors on the inside of the ring.

The Outcome

Candle in the Wind (Version 001)

Week 2’s assignment for Light and Interactivity is to replace the look and feel of a candle, without the use of a flame. In class we were given an Adafruit Jewel; seven NeoPixels in a circle.

What does it mean to be a candle?

For the first prototype, aside from the colours within a flame I focussed on 3 elements of my reference candle:

  • The interactivity: how it feels to turn a candle on and off.
  • The intensity of light at various parts of the flame’s life.
  • The texture: The general shape and texture of the flame, what is opaque, what is transparent.

In reverse order from above:


The first thing I noticed about the candle’s flame is that there’s a section of transparency above the wick, with the brightest part hovering a bit above that. I tried to recreate this effect using rods of refractive acrylic, which I sanded near the top and left clear at the base. Hot glue offered a good way to stick the rod to the pixel with a bit of flexibility; permanent enough to hold but not so permanent as to damage the pixel if I chose a different direction.

Unsanded Rod
Sanded Rod

Intensity & Colour

Different parts of the flame flicker differently. In general, unless there’s a strong disturbance, the core remains a bright, mostly consistent yellow, perhaps with a relatively low frequency flicker. The parts around the core flicker more quickly from yellow to orange, and by the tip even red.

I tried to recreate this effect by giving each pixel its own HSI array, and then flickering/fading each pixel according to its own values. It involved a silly amount of arrays. The pretty messy code (it’s a prototype!) can be found at this GitHub link.


The class is called Light and Interactivity after all, so I figured I would have a bash at replicating some of the emotional investment that you put into a candle. With candles, you don’t just flick a switch or wiggle a wire to turn them on or off. You have to go through the process of lighting a match and holding it close to the wick. Maybe the first go doesn’t do anything. Then to turn it off you must blow it out, but just in the right way. How many of us know the struggle and embarrassment of failing to successfully blow out all the birthday candles on our cakes??

To try recreate this feeling, I split my sketch up into 4 sections. 1) Off. 2) Turning On. 3) On. 4) Turning Off.

While in Off, the sketch listens for a high light threshold on an LDR (intended to give the experience of ‘holding a match’ to the wick). This activates Turning On, which runs over a set time. After completing, Turning On transitions to On. While in On, the sketch listens for input from a microphone pretending to be a wind sensor. Blowing on the wind sensor affects the Intensity values of each pixel, but they will return to full brightness unless a high threshold is met. Once the threshold is met, the Turning Off sequence activates and the sketch comes to an end.

The high threshold for the wind sensor trigger has the added bonus of making it a bit difficult to blow out the candle. I stumbled upon this effect accidentally, but it definitely feels to me as if I’m trying to blow out an obstinate candle irl.

A few notes about the video above:

  • The ‘Turning Off sequence fades the LEDs from the outside in. My goal is to recreate the appearance of a dying ember.
  • Right now the fade is a bit jagged; the values are jumping down in chunks over discreet intervals, which gives a staccato appearance to the fade. While I’d love to fix this asap, I’m considering it an ‘edge case’ for this version; something that would be nice but it not essential to the core of the experience I am trying to create.
  • I have a handy line of code void(* resetFunc) (void) = 0; which allows me to reset the sketch at the end of the cycle, easily setting up the candle for another go.

Powering an LED (round 3)

Last semester I got really into powering my fabrication projects with human power. This in turn built off a project I made a year or so ago, a hand cranked LED sign. All of these were kind of hacked together, so I look forward to approaching energy generation in a more formal context for this class.

The projects mentioned above all use DC motors to generate power, so for this week’s assignment I asked the group if we could experiment with stepper motors instead.

It wasn’t difficult at all to plug in an LED to a 5V stepper and get it to turn on. The really surprising thing was that is didn’t seem to matter not only which direction you wired the LED (which makes sense as the stepper current alternates), but even which wires you plug it into. That was very surprising to me, I look forward to discussing how that happens more in class.