Capacitive Touch With Bigger Contacts

I’ve been messing with these small and inexpensive capacitive touch boards. Pro: small. Con: small.

I wanted a bigger touch surface, which could also act as enclosure. Ran across these “bath bomb” molds. They come in various sizes and are aluminum.

As is my way, I added another LED (though, it barely shows at the bottom) and haptic feedback (phone/pager motor).

Going to use the same design with a Kenwood style headset plug, so it can be used to trigger FRS & Ham radios. A big Push To Talk.

No need to solder to the aluminum (it will just suck up heat). I use a strip of copper foil tape between the board and the “bell”. I use this tape when I encounter odd wiring situations. Very handy.

Robotic Arms And Snakes

I’ve always loved robotic arms. One of my favorite toys was a Radio Shack Armatron. Which was quite a piece of mechanical engineering. No servos or steppers in it! Instead, it had a continuous running DC motor engaged to a series of clutches, gears, and other mechanical connections. All the “oomph” was in the base. Power was then transferred to the parts of the arm. I learned this, of course, by taking mine apart. You learn so much by taking things apart. I highly recommend it.

Well, most of the robotic arms these days solve the problem, in my opinion, incorrectly. They put motors everywhere. Tiny servos in the “fingers” more servos at each joint. All of which take up a lot of space and weight.

Why incorrectly? Because many seem to ignore millions of years of biological evolution. Do you have motors in your fingers? Are your fingers very muscular? How can your relatively small fingers hold your entire body weight? Because the strength isn’t in the fingers — it’s in the forearms. Tendons do the dirty work. The power is located in another section of the arm. Where it’s okay to be bigger.

So, when working on a project which would require robot arm-like movement, and be small, and flexible, I went back to nature, and groundwork laid by some pretty heavy-duty industrial uses. I went to the snake.

Instead of a series of motors in the arm, there are mounting points for steel cable. The cable feeds down the arm to an array of motors and their controllers. The motors “push” or “pull” the cable to flex the arm. Want it to flex at another point? More wires. and motors

It can get complicated really quick, and control needs some fancy math, but you end up with a very flexible arm which can fit into unusual spaces. For example, large versions of these have been used to access the cores of nuclear power plants. They are also used to inspect and clean the insides of jet engines. Places were human hands can’t reach and traditional arms too clumsy.

This is not to say that more traditional servo driven arms aren’t great. They are used all over the place. But, for some situations, you have to go back to nature and follow the advice of millions of years of development.

It’s early days, and I may very well give up on the snake idea, given its own complexities. Mother Nature is very much “smarter” than me. But, sometimes, you have to attack a problem from a different angle. Or with a snake.