How would you register the sligtest touch?
October 26, 2011
I have an idea for a really fantastic little project (IMO :) I'll show it later, but I have run into a little challenge that I did not see when I woke up in the middle of the night with the overal concept crystal clear in my head.
I need a "probe" - a small thin stick - like a long fat needle - to move forward towards an object, and with none, or only a slight touch, register when it touch the object.
Now, in my dream that was easy, because I'd just make some form of push switch; Either out in the end of the probe, or at the other end of it -- A mechanical sollution, simple, no problem.
However, in reality it turns out that this object to be touched quite often is rude enough not to be at a right angle to the probe, and so it is just sliding off, which is devastating for the project.
Imagine a ping pong ball, with a knitting needle moving towards it like a rocket - only very slowly :D I need to know when that needle touches anywhere - even the outside edges - of that ball.
I do not mind what the needle is made of (could be a laser, or a tentacle from a space monkey, what ever, just that long thin shape) - and I just need to know when it is touching something.
A good idea would be to make an apparatus shaped like the letter U, with a laser on one end, pointing towards a sensor in the other end. That would give the effect: Put down the ping pong ball between the two, and you would interrupt the laser, and know someting was there.. Only that would not do, because I need to know the distance - how far did the needle go before it touched the freakin ball.
I made a mechanical solution with a combined touch-and side-move switch, reistering when the needle is either stopped, or pulled slightly to one side or the other. I just do not hink it is very elegant.
I cannot hook up the ping pong ball with electric current, though that would be a perffect solution: The instant the needle touch the object, a current could flow. But electrifying the object (ping pong ball in the example) will not do.
Damn, I am stuck on this one. I keep moving my finger slowly towards stuff, and sense just the moment I touch it. Why can I not do that with a sensor? (No; HOW do I do that with a sensor?)
I think I will send a present to the person who can give me a good idea here :)
First I want to thank you all for some excelent thinking! I was merely hoping to get a single respond, and figured that perhaps it could inspire me to think different.. but I received some very, very good and concrete ideas, really fast!
You guys are very talented and nice persons, thank you :)
Then, since you take me so serious, so you actually come up with good ideas, I figured I'd better share my idea:
I had this idea: Did you guys see the Tintin cartoon, where the professor makes a machine to copy things? He has 2 plates, on one he places an object, and the machine copies it to the other. I would like to make something like that :)
If I made a very simple system that would enable a probe to poke at all possible angles on a rotating object - just by using 3-4 servos in total, not regarding angles much, just making sure the the object was poked in all sorts of angles and directions, one servo step inside another servo loop at a time.. Could take all night! Poke, change angle, poke, poke, poke..
When the probe reaches the object, it instantly retracts, servo moves, and the next point, just somewhere next to it is touched.
Where would that take us?
Well.. Based on the fact that 2 servos whith the same signal will move the same way, I would just make 2 of these machines. Only the other would have a drill instead of a probe. And instead of the object, a block of an easy to drill-material should be.
Drill till the surface on the sensor was reached, drill, baby, drill. From that direction, and from that :D
The 2 machines could have long wires between them, one in another house. Almost teleportation! :D And since it's only simple servo signals, it would be easy to transmit over air as well. Or hey - over the Internet?
And as the machines would be made by simple servos, you could build one as well, and I could teleport my shape to your machine :D
And what about detecting colors on the tip as well? And on the shaping-end, an ink-jet head. That would be sick!
When done with the copying things, instead of a surface detecting probe, I could place perhaps a light detection. And then I could physically shape the rays from a flashlight shining on a diamond-shaped crystal..
Or how about sensing magnetism, and shape it in ral form?
Heck, place a noisy speaker there, and detect sound, see how it would go out from the speaker :D
But first I wanted to copy objects, and I need a good way to detect them. I could use laser, see when the ray was broke, but that would not give me "introvert" shapes - only the outsides of a cup, not the insides..