The Make Something Every Week Contest

[ceptimus]

I took a break from Sudoffle programming to design, 3D-print, and code this little two-servo clock.



It uses two cheap servos to drive the hands, and a cheap ESP8266 board to connect to WiFi and get the correct local time from an internet time server.

Total parts cost less than ten dollars.

Of course, I don't need yet another clock, but it was interesting designing it.

[ceptimus]

Rolling ball divert gate separator - YouTube

[JoeP]

The public demands to know why the first ball bearing needed to be separated. Is this some kind of monarchy, 1%, capitalist situation? Or is the isolated ball bearing being othered, marginalised, sent to punishment camp?

[ceptimus]

It's for a clock that measures the passage of time by 'counting' balls, and displays the time by the position of the balls.

There's a rollercoaster type track, with an elevator mechanism that delivers one ball to the top of the track each minute. The balls roll around the track and accumulate at various resting places. When a certain number of balls accumulate at one place, there is an 'avalanche' and all those balls are released.

It would be possible to have an accumulation of up to sixty balls to count the minutes, then, when the avalanche occurs, by separating one ball from the train of sixty, there's a branch line from the main track that only receives one ball per hour.

My design doesn't do that 'divide by sixty' thing. Rather the first avalanche station divides by five, the second one by three, and the last one by four. This gives avalanche cycles every five minutes, quarter of an hour, and hour respectively. You can see how this corresponds to a normal clock face, where the numbers one to twelve are spaced at five-minute intervals for the minute hand.

I can also have the rolling balls hit little 'bells' as they roll past, resulting in hourly, and quarter, chimes.

[JoeP]

I'm assuming there will be a live stream / slow TV event when it's finished, just showing the current time?

[BrotherMan]

[viscousmemories]

I don't know what voice you had in my head but it wasn't that one. Cool invention!

[Ensign Steve]

Who knew Sir Michael Caine CBE was a member?

[Sock Puppet]

Odd, that was p. much exactly the voice I had in me own 'ead.

[ceptimus]

I've been doodling this somewhat complex 'waterwheel' for the balls. The idea is that the balls enter on the little side-arm track (foreground of the image) and then roll down the spokes towards the centre of the wheel. Once five balls are present, an overbalancing mechanism (not shown here for simplicity) causes the wheel to rotate anticlockwise, one twelfth of a turn, and the balls roll back off towards the left.

By altering the position of every third stop (near the hub) then there's not enough room for all five balls to fit on the 'spokes' and the fifth ball is trapped on the entry platform. As the four balls roll off, they push the fifth ball back out the way it came in (but lower).

It's something of a cheat, but saves a whole wheel - this way I only need the minute hand wheel and the hour hand wheel, plus the external roller coaster track and the elevator mechanism.

I think I'll build this one first, and then maybe make a three-wheel ball clock to follow (unless I become bored with ball clocks).

Not shown here are the numeral ring and other niceties.

[ceptimus]

I'm still working on the ball clock, but I took a short break to make an external battery backplate adapter for my LEGO Mindstorms NXT set.

This is the brick "brain" of the Mindstorms NXT



Here's a view on the back



As standard, it's powered by 6 AA batteries



But it eats the batteries very quickly, and even using rechargeable AA cells is a hassle because you have to take them out to recharge them, and when the brick is built into your robot, that's a hassle.

I designed this



Here it is printed, with some bits of tinplate for the battery contacts in place, and some wires to an external battery connector



Here's how it fits





I tested it out on the Mindcuber (not my design) which solves Rubik cubes.



I should upload a video of the Mindcuber in operation?

[Ensign Steve]

YES

[ceptimus]

LEGO Mindstorms NXT Mindcuber, solving Rubik...

You can find the design and code online. Just search for Mindcuber. It's available for all the generations of the LEGO Mindstorms kits. Mine is one of the older NXT kits. The designs for the newer kits solve the cube faster - because those kits have more processing power in the "Brain", and some have the option of controlling an extra servo motor.

[viscousmemories]

[Ari]

I assume it will just error out, but I do wonder what will happen if it’s given a cube with switched stickers so that it’s in an unsolvable configuration, or with two central colors the same?

[Ensign Steve]

Some people just want to watch the world burn.

[JoeP]

[ceptimus]

Originally Posted by Ari

I assume it will just error out, but I do wonder what will happen if it’s given a cube with switched stickers so that it’s in an unsolvable configuration, or with two central colors the same?

It just stops and says 'cube error' on the display.

Here's the video (not mine) showing cube solving robots built from three different generations of the LEGO Mindstormer kit.

3 Generations of Lego Mindstorms Mindcuber Rubiks...

http://mindcuber.com/

I've modified mine since filming my video, to solve more reliably. Main problem was a loose fit of the cube in the turntable. Awkward to make it fit better because moving the rails in by one 'LEGO hole' made it too small. I solved that problem by using a diagonal construction to hold the corner posts. With a regular construction the diagonal must be sqrt(2)*side length, so 1.414 * some number of holes, but with a diagonal construction it's a whole number of holes. Lego Technic parts are not really designed for diagonals - especially when the floor of the turntable needs to be smooth to allow the cube to turn over smoothly, without catching. After building four prototypes, I figured out a way to do it. I could just 3D-print an optimal turntable - but that would be cheating! The robot *MUST* be made only from standard LEGO Technic parts.

[Ensign Steve]

My weekend project: I made a sketch in Processing to model the 60 possible orientations of my 12-sided rubik's cube.

Will this be useful to me in some way? Who knows!

[ceptimus]

I've been investigating the Bluetooth functions of my old LEGO Mindstorms NXT brick. I've written some Python code on a PC that allows me to control the Lego motors using the NXT as a slave, with the Python making all the decisions.

Now, I want to try controlling it using an ESP32 Cam. This is a small, very cheap, microcontroller with a built-in camera - and it also has WiFi and Bluetooth connectivity. If I can get it to work, I can use its camera to capture the state of a Rubik cube, the ESP32 should be able to solve the cube in less than a second, using Kociemba's two phase algorithm, and then it can send the solution (typically only 18 face twists) to the slave NXT to actually make the moves. Because the NXT won't need to scan the cube itself, it frees up a motor, allowing the robot to have a better cube-gripping and turning mechanism.

Lots of ifs remain. It may turn out to be too difficult a project for me.