Comments on: Hackit: The Bronco Table

By: rjk

rjk — Thu, 28 May 2009 17:24:37 +0000

Check this out… it’s a piece of fabric and a piece of antistatic plastic that’re combined and used to detect pressure.

It can light a LED, maybe it can trip a relay or something and set this table in motion.

By: bugloaf

bugloaf — Tue, 08 Jul 2008 21:14:40 +0000

There are a lot of interesting ideas here, but I haven’t seen the one that I thought was obvious: Use an accelerometer chip to detect the deflection of the table when you put something on it. It should easily be sensitive enough. In fact you will probably need your software to filter out small vibrations so that just walking by the table won’t set it off. Just search Digikey for “accelerometer” and you will find hundreds. They’re small and cheap and come in IC packages.

By: ard

ard — Thu, 03 Jul 2008 13:55:51 +0000

Solder a pin to the center of a piezo buzzer (flat, round) perpendicular to the surface of the copper side. Solder a mic ground lead to the other side of the copper, the signal lead is soldered to the center of the piezo material. Connect the mic lead to an opamp. Poke the pin in the center of the bottom of the table. An opamp based amplifier (very high impedance) will detect even a flee landing on the table top.This setup works for high frequencies (it will act as a giant ear) as well as for low frequencies (it can detect earthquakes.) Multiple sensors, one in each leg, might be needed to reject false positives.

By: jz

jz — Sun, 29 Jun 2008 00:47:09 +0000

Rip the guts out of an electronic bathroom scale.

By: jz

jz — Sat, 28 Jun 2008 02:10:15 +0000

Build a bridge out of her! Seriously though just make the table square and use a touch screen monitor for the table top. Would allow for other cool stuff too if ya think about it.

By: TheKhakinator

TheKhakinator — Fri, 27 Jun 2008 19:15:19 +0000

Capacitive sensing, easily. They’d detect anything /placed/ on the table because even if the object was tiny, your hand would change the capacitance if it touched the table.

By: brett

brett — Fri, 27 Jun 2008 09:55:24 +0000

@#16, tgbm said:
With the current mic configuration... would it be possible to trigger the table with a clap, snap, sneeze, or some other loud noise of the same sort?

This is mainly why I opted for a microphone rather than a pressure sensor- it allows the table to sense beyond just what's on the table top, and allows it to be a little more unpredictable. You could also fool it if you could noiselessly put something on it. It's not so much that it wouldn't let you put anything on it, but that you'd have to meet it on its terms rather than yours. I think the main issue is the surface of the table, and how good of a transmitter of vibration it is. I'm also not amplifying the signal from the piezo, so it would probably benefit from that. Thanks so much for such thoughtful comments, everyone!

By: brett

brett — Fri, 27 Jun 2008 09:24:04 +0000

thanks for the suggestions, everyone! I guess I’ve got my work cut out for me.

By: g3n3tix

g3n3tix — Fri, 27 Jun 2008 01:57:39 +0000

Friggin’ laser beams.
They form a grid, and if they are cut, that means there is an object. Needs a lot of lasers, and complicated.
Doable ?

By: dan fruzzetti

dan fruzzetti — Fri, 27 Jun 2008 01:48:00 +0000

Some of the ideas posted are cheap and available. Others are far less utilitarian (e.g. a border of photo cells does NOT a multi-touch display make, especially when multiple contacts are collinear, except at an exceedingly high density and directionality of sensors).

My suggestion? Hypersonically vibrate the table surface at or near a multiple of its resonant frequency. It could in principle pick up the damping effect of a hair or speck of dust.

By: Cyrus

Cyrus — Fri, 27 Jun 2008 00:46:06 +0000

Just an idea, not sure if it will work. Basically set up a capacitor across the length of the table and detect changes in electrical conditions caused by putting an object in between- basically introducing a dielectric. The problem might come in changes in humidity and the like.
Or, maybe RF modulators can be used- something like a theremin, using the heterodyne principle. I’m not sure it would work with all materials, though…

By: JFH

JFH — Thu, 26 Jun 2008 22:22:50 +0000

Make a big capacitor. A big piece of unetched PC board material, or even an aluminum/paper/aluminum sandwich. You could probably hook right to the existing microphone input. You get a nice little current spike from
d(C*V)/dt.

By: Alex

Alex — Thu, 26 Jun 2008 21:54:54 +0000

Use some sort of LED multi-touch setup, where you use the LEDs as emitters and detectors. That was, it would detect anything, and while its running away it can display text and/or devil faces.

Here is an example of how the electronics would work: http://cs.nyu.edu/~jhan/ledtouch/index.html

By: BigD145

BigD145 — Thu, 26 Jun 2008 21:50:31 +0000

If you us a camera, you may also be able to fix the following and avoidance bit. You use a wide angle lens up close to a glass topped table and then just follow or avoid largish moving shapes. Black and white is good enough. It wouldn't be able to avoid obstacles, but would follow or avoid any moving body.

Avoidance: If it was already in motion and came across a dresser or sofa edge or something, it would see it as a moving body and would then move away. Eventually it would find itself in the middle of the room, away from all furniture.

By: TGBM

TGBM — Thu, 26 Jun 2008 20:34:06 +0000

Just a question,

With the current mic configuration... would it be possible to trigger the table with a clap, snap, sneeze, or some other loud noise of the same sort?