I have a small remote control like device with about 11 buttons. The centers of each button are placed about 1.1cm apart, and each are about 0.7cm in diameter (this means about 0.4cm between the edges).

For various reasons, I'd like to use LEGO Technic to build a mechanism that can press these buttons.

What is a basic approach I can use to build this?

I've only got a few Lego parts on hand to experiment, and not enough to do anything with, so it's mainly been a mental exercise. Before I go out to buy more, I'd really appreciate some direction in what I can do, so I know what to purchase.

  • 2
    Hi @tamsanh! A few questions to clarify: Are the buttons arranged in a grid, along a line or in a different pattern? Could you post a picture of this device? Are you looking for a mechanism to press any given button on demand (as in a LEGO remote for your non-LEGO remote) or rather program a sequence to press automatically? – zovits Jan 9 at 8:43
  • Hi @zovits! They are aligned in a grid for the most part, with two buttons slightly offset. The sequence in which they would be pressed will be arbitrary. The plan is to send data to a controller to press whatever combination is required at whatever time. – tamsanh Jan 26 at 14:17
  • In that case, you can use any 2 axis system (X-Y or polar, but the first is more suitable for the grid arrangement) to position a "finger" above the correct button and a third motor to move the "finger" to press the button it is hovering over. In order to position the "finger" correctly, I'd recommend investing in a Mindstorms set, either the NXT or the EV3 variant contains motors with built-in encoders that allow for precise positioning. If you have any other questions, don't hesitate to ask them, I'm curious what will you build! – zovits Jan 27 at 17:50
  • Hey @zovits, thanks for the tip. To be honest, I already have a CNC like machine, and it has been subpar in its performance, hence my wish to move to direct actuation. Perhaps that will have to be a separate topic, haha. – tamsanh Jan 29 at 16:46
  • What do you mean by "direct actuation"? Do you wish to have a separate actuator for each button? That would require either 11 actuators or some kind of demultiplexer, be it a mechanical switch (akin to a gearbox) or a pneumatical system with 11 pistons and the corresponding number of valves (and of course their actuators). – zovits Jan 29 at 16:49

The simplest solution I can currently think of is to use a linear actuator to push the buttons down because they are compact, strong, and have a lot of pushing force.

You can either have one actuator per button or use worm gears to finely move the actuator over each button. This would have to move in both the X and Y direction however because the buttons are in a grid, which is a little more complicated but possible.

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