Rubick's cube radio - small, cheap, ultra low power receiver suggestions

Greetings,

  1. We are trying to make an open-sourced LED Rubick's cube which a child can "instantly" scramble every ~30 seconds with a stand-alone arduino kit.

  2. ===> QUESTION Each Rubick's cube needs 20 individual close-range radio-bluetooth-IR receivers that are: small, low power, low cost & low radiation. (each of 20 little cubies has: LEDs, battery, receiver). What do you recommend?

  3. Additional info

Really only need receivers (not tx) for each cubie

  • For fitment, the BLE Nano (nRF51822) sold on arduino.cc aka redbear Bluetooth 4.0LE board (18.5 x 21m) just fits (but it is too expensive and big size will force smaller batteries)

  • The cube will be right next to the arduino so radio distance and noise are not really issues. Some early ideas:

* [edit] NRF51822 bluetooth BLE 4.0 module (no wifi) seems to be among the lowest power consumption receivers out of the box. Any opinions here?

  • Via audio spectrum with microphones embedded in each cubie (maybe a nonstarter with WS28xx timing tolerance and ambient noise?)

* Via IR with photoelectric sensor embedded in each cubie (maybe a nonstarter with cube's WS28xx strict timing requirements and interference from Rubick's cube LEDs/ oil from player's hands?). Also cube might fail with more holes. Killed based on recommendationof @Robin2

  • Tweaked LM393/ LM358 (see jlettens post here)

  • ESP8266 / ESP32

Radio-bluetooth-wifi is definitely not my forte so appreciate any macro level guidance here!

RunningFast: 2. Each Rubick's cube needs 20 individual close-range radio-bluetooth-IR receivers that are: small, low power, low cost & low radiation. (each of 20 little cubies has: LEDs, battery, receiver)

A couple of things I don't understand here.

Bluetooth is NOT the same as IR - so which do you really mean? And what is it supposed to receive?

Why do you need 20 of them? Can't a single device receive all the data?

...R

Thanks Robin for your detailed questions.

  1. We are looking for some general suggestions as to best way to get data from the nearby Arduino to the Rubick's cube. Ideally an optimization of size/ power consumption/ price / very basic receive only. The cube is receiving very little data in bursts, although the WS2813B is a strict about timing (at the beginning at least).

To be more clear, when the player finishes solving after (say every 15-45) seconds, he or she will tell the arduino to send a new LED pattern to the Rubick's cube. So arduino will send color codes to each of the 48 assignable LEDs (9*6 sides-6 middle).

  1. I don't think a single receiver-battery solution for the whole cube will work but if someone can think of a better alternative kindly let me know.

This is because the player shuffles the little cubies all around the Rubick's cube, so centralized power and data cables would get tangled. Contact brushes between cubes are not practical as the kids turn the cube very fast and disruptively, the plastic is delicate, and the turning friction is carefully calibrated/lubed.

Interesting FYI - Each Rubick's cube has 26 little cubies (3x3x3-1 invisible "core"). Interestingly, the 6 middle colored cubes are always in the same relative place so are always the same color. Hence 20 (26-6) receivers required.

I made a small and simple IR receiver with a DIP Attiny45 and a TSOP4838 IR receiver to fit into an N Gauge model train wagon. You could probably use a smaller battery than I did (maybe a coin cell) but I think it would be hard to fit it into one cude of a Rubik’s cube - unless you deliberately make the cube big enough. Maybe if you know how to use surface mount components you could greatly reduce the size.

But even if you got that figured out I would not be surprised if some of the receivers could not get a signal from the IR transmitter - on the back side of the cube or shielded by a hand.

An you would have to be able to take the cubes apart to replace the batteries - probably every day.

…R

Thanks again Robin

Robin2: I made a small and simple IR receiver with a DIP Attiny45 and a TSOP4838 IR receiver to fit into an N Gauge model train wagon....But even if you got that figured out I would not be surprised if some of the receivers could not get a signal from the IR transmitter - on the back side of the cube or shielded by a hand.

That experience shows IR is not convenient, so let's remove that option.

Leaving principally bluetooth or some type of radio-microphone as options.

With only the benefit of internet search results, the NRF51822 bluetooth BLE 4.0 module (no wifi) seems to be among the lowest power consumption receivers out of the box...

Robin2: You could probably use a smaller battery than I did (maybe a coin cell) but I think it would be hard to fit it into one cude of a Rubik's cube - unless you deliberately make the cube big enough. Maybe if you know how to use surface mount components you could greatly reduce the size.

...An[d] you would have to be able to take the cubes apart to replace the batteries - probably every day.

A pair of CR2032 would fit in each of the cubies and provide several day's of power. But they would require frequent and painful replacement. Bad for the environment and bad for the wallet. Rechargable LIR button cells have 1/6 the power, unfortunately.

We can use a small lipo battery per cube that can be recharged every night.