If you’ve ever wanted to build a large format plotter but didn’t have the floor space, maybe put it up against the wall and make it cute. That’s the idea behind Fumik, the wall-drawing robot. As you might expect, the little device is just a motion base with a pen. We hope there’s paper against the wall since not everyone wants computer-generated art on their drywall.
The maximum size is apparently 5 m wide by 3 m tall, plenty of room to express yourself. The controller is an Arduino Mega, and stepper motors with a CNC shield drive the whole assembly. Interestingly, the motor and electronics are all onboard the jellyfish itself, rather than the wall.
The device only holds one pen at a time, but you can draw with one color and then manually change the pen. The files on GitHub are good, but you’ll need to intuit some of the mechanics from the videos. However, since it uses off-the-shelf hardware, it should be pretty easy to figure it out. This looks like a cheap and cheerful wall plotter, and the results speak for themselves.
Every high school physics student knows c, or the speed of light, it’s 3 x 10^8 metres per second. More advanced or more curious students will know that this is an approximation, and the figure of 299,792,458 metres per second that forms the officially accepted figure comes from a resonance of the caesium atom from which is derived a value for the second.
Galileo Galilei, whose presence in this story should come as no surprise. Justus Sustermans, Public domain.
But for those who are really curious about measuring the speed of light the question remains: Just how did we arrive at that figure and how long have we been measuring it? The answer contains some surprises, and some exceptionally clever scientific thought and experimentation over the centuries.
The nature of light and whether it had a speed at all had been puzzling philosophers and scientists since antiquity, but the first experiments performed in an attempt to measure it were you will not be surprised to hear, performed by Galileo sometime in the early 17th century. His experiment involved his observation of assistants uncovering lanterns at known distances away, and his observations failed to arrive at a figure.
Later that century in 1676 the first numerical estimate of the speed of light was made by the Danish astronomer Ole Rømer, who observed an apparent variation in the period of one of Jupiter’s moons depending upon whether the Earth was approaching it or moving away from it. From this he was able to estimate the time taken for light to cross the Earth’s orbit, and from there the mathematician Christiaan Huygens was able to produce a figure of 220,000,000 metres per second.
Spinning Cogs And Mirrors: Time Of Flight
The mile-long evacuated tube used in Michelson’s time-of-flight experiment. H. H. Dunn, Public domain.
The experiments with which we will perhaps be the most familiar are the so-called time of flight measurements, which take Galileo’s idea of observing the delay as light travels over a distance, and bring to it ever higher precision. This was first performed in the middle of the 19th century by the French physicist Hippolyte Fizeau, who reflected a beam of light from a mirror over several kilometres, and used a toothed wheel to chop it into pulses. The pulses could be increased in frequency by moving the wheel faster until the time taken for the light to travel the distance from wheel to mirror and back again matched the separation between teeth and the returning pulse could be observed. His calculation of 313,300,000 metres per second was successively improved upon through the work of succession of others including Léon Foucault, culminating in the series of experiments by the American physicist Albert A. Michelson in the 1920s. Michelson’s final figure stood at 299,774,000 metres per second, measured through a multi-path traversal of a mile-long evacuated tube in the California desert. In the second half of the century the techniques shifted to laser interferometry, and in the quest to define the SI units in terms of constants, eventually to the definition mentioned in the first paragraph.
The most fascinating part of the story probably encapsulates the essence of scientific discovery, namely that while to arrive at something takes the work of many scientists building on the work of each other, it can then often be rendered into a form that can be understood by a student who hasn’t had to pass through all that effort. We could replicate Fizeau and Michelson’s experiments with a pulse generator, laser diode, and oscilloscope, which while of little scientific value nearly a century after Michelson’s evacuated tube, is still immensely cool. Has anyone out there given it a try?
A lot of Samsung Galaxy users think that Samsung has been throttling smartphone performance, so much so that they don’t live up to their published specifications. At issue is the game optimizing service (GOS) which is intended to throttle the CPU while playing games to prevent overheating. S22 owners have recently discovered that it’s not only games that are throttled, but there’s a list of over 10,000 apps which are subject to GOS control, and there is no way to disable it.
What they’re really upset over is the fact that popular benchmarking apps are not subject to GOS throttling — something that’s hard to see as anything but a blatant attempt to game the system. In fact, this past weekend the folks at Geekbench banned four generations of Samsung Galaxy phones (S10, S20, S21, S22) for benchmark manipulation.
Admittedly, thermal management is critical on today’s incredibly powerful handheld devices, and the concept of throttling is an accepted solution in the industry. But people are upset at the opaqueness and lack of control of GOS, not to mention cherry picking apps in order to excel at benchmarks. Furthermore Samsung has removed their vapor chamber cooling system from recent models. This makes GOS even more important and looks like a cost-savings measure that may have backfired. Currently there’s a petition with the government claiming false advertising, and users are actively pursuing a lawsuit against Samsung.
[EEforEveryone] is trying to find a good hot plate for reflow soldering. After trying one cheap unit, he got another one. He was a bit underwhelmed. The grounding was suspect and the bed wasn’t totally flat. He tore it apart and was surprised that there was very little inside. While the construction wasn’t perfect, it was better than the previous unit. You can see a video of the teardown and review below.
Before powering it up, the first order of business was to rewire the ground system. After that, it was time to try it. However, by confusing Fahrenheit and Centigrade, he set the temperature much higher than necessary which creating a little smoke. Fixing the temperature helped, but there was still a bit of a smoky smell that eventually subsided.
The verdict? The hot plate worked well enough, but you probably do want to check the ground wiring before using it. That’s often a good idea where cheap equipment is concerned, anyway. But the real takeaway is that it looks like you could homebrew something equivalent without much trouble. The controller is an off-the-shelf module. A switch and a plug aren’t hard to figure out. The heating element could be a silicone heater or PCB heater meant for a 3D printer.
Of course, there are other options. You could use a wok. Or why not a waffle iron? You can also make a custom PCB.
