Matrix Of Resistors Forms The Hot Hands Behind This Thermochromic Analog Clock | Hackaday

If you plan to give up your job, you might as well take a big step forward.

Maybe most people will try this way, but [Daniel Valuch] obviously really doesn't want to go to work that day.

The idea here is simple: add some current to the resistor to heat the resistor, and put some thermochromic film on the resistor to get a pixel. The next part is not so simple: expand a single pixel into a 32 x 32 matrix.

To make each pixel square, [Daniel] chose to pair 220 ohm SMD resistors to use up to 2,048 components. The choice of using 1,024 bit shift registers made of discrete 74LVC1G175 flip-flops to drive them adds complexity. With the help of Arduino Nano and all other supporting components, there are more than 3,000 devices that may draw 50 amps. These people are stupid or unfortunate and cannot turn on every pixel at the same time. Fortunately, [Daniel] chose to simulate an analog clock here. This leads to other problems, such as handling the cooling lag of the thermochromic film when the pointer is moved, which must be handled in the software.

We have seen other thermochromic displays before, including the most recent

. This display may not be the highest resolution display currently available, but it is big, bold and slightly dangerous, which makes it a big win in our book.

1) Get a huge pet food

2) Place 1024 heating element arrays under it

3) Placed in an environment of 10°C

4) Turn on the pixels at 30C

Congratulations, you can now print bacteria on the petri dish

You can use...life to implement Conway's "Game of Life".

Interesting project, interesting scale! well-done!

If diodes are used instead of resistors, multiplexed drivers can be used.

Well, if you use matrix and multiplexing, you can make it simple. But why should it be simple? Then, you don't need 1024 triggers. There are many ways to do it, and I like simple but highly repetitive patterns. It is very pleasant to see :)

Very interesting project and well built.

The thickness of the PCB looks like a regular 1.6mm. I thought that using an ultra-thin thickness (such as 0.6mm) would greatly reduce the cooling time. Similarly, replacing the super expensive 2512 with a smaller package (0805) will also reduce thermal inertia, because you only need to raise the temperature above the threshold.

By the way, is there room temperature measurement for software current control/compensation?

What is the average power consumption of the display time?

In addition, since it seems that the main purpose is only to display time, why use an orthogonal matrix? Similarly, if there is no quadrant + dial configuration and only two different pointer lengths, it will again greatly reduce the BOM.

0805 is cheaper, but if you want the same size clock and pixels, you need more clocks and pixels, and the difference is that the price is not much. The pixels do not look good either, because black lines appear between the resistors.

The PCB is actually very thick, 3.2mm. The first is for structural reasons, but when designing, I worry that excessive heat leakage will stain the pixels, and the pixel power may be insufficient. It turns out that if you allow transient seconds, 250mW is enough. We go to see it in winter.

At 4.6V, the total power consumption is about 8A. The trigger can be reduced to below 3V by the power supply voltage, which is a good way to regulate winter/summer

Nice project! It would be fun to make a version with IR LED, so the smartphone camera can see it, but not the naked eye. Allow anyone to interact over the phone instead of dedicated Fluke.

Write down good ideas and good progress!

Does anyone know how much heat the resistor actually generates?

Quoting from the linked project page "The pixel is made of 2512 size resistors, each resistor dissipates 250mW (5V/50mA)", all of this is dissipated as heat, unless you increase the power a lot, it's like 99.5% Calories, 0.5% orange light.

I misread the title and thought it was an infrared camera clock, so it can only be read by an infrared camera. Actually more useful

Wow, my AWLAYS wants to do this! Glad to see you did it! ! !

I want to know how much power is needed to use it for the intended use case. Manually calculated from the attached photos, it seems that about 100 pixels (10% of the entire display) are lit, and the author said that greasy things can consume 250W, so I assume that the power consumption of "clock mode" is 200-250W, but I think it depends on whether the pixel needs to run at 100% heat to make the image come out.

I want to know the actual figures.

You can use heating lamps installed on the ceiling of a large building full of people and project the matrix of the heating area, so that if people want to keep warm, they tend to move them to the heated part; if they need to keep cool If you do, you can avoid them. People's ceilings and where they are willing to stand can also be used as clocks. :-) Annoying sound from a speaker matrix or a matrix of wi-fi access points without power but low power, you may have the same effect.

Chicago-Does anyone really know what time it is? (Does anyone really care?)

This is one of the coolest projects on Hackaday. I bet you can increase the resolution by cutting the thermochromic film into 32×32 small and independent square grids while reducing bleeding and input delay.

The technology is incredible and you can easily shrink it to have a nano-pixel display. You can also display the volume by adding resistors to solid blocks of transparent thermochromic material.

If you don’t have a thermochromic material, you can use lard – it is opaque and white at room temperature, it is transparent and brown when heated: D

I added some videos on YouTube

Very very cool. I have done some research on thermochromic materials. Sadly, they are made of highly toxic chemicals, have a rather limited life span, and are very sensitive to ultraviolet light. Thermal cycling will also rapidly degrade the material, which is what we need to do. Within 6 months, the display will fade dramatically.

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