Touch Sensitive Cement with Just a Dash of Neon

For quite some time now we’ve seen people casting their own countertops and other surfaces out of cement. It’s a combination of mold-making and surface finishing that produces a smooth and durable surface at quite a low cost, if you don’t factor in damage done to your back when lifting the thing for installation.

This offering is a little bit different. [Elliott Spelman] built his own touch sensitive cement table top. When you place your grubby hands on the polished surface, a loop of neon lighting is switched on. This is thanks to a 4:1 mix of quick setting cement and iron oxide powder. Bare copper wire was laid around the edges of the surface to be encased by the cement for making connections later.

There were some sad moments when [Elliott] was removing the cast surface from the mold. He ended up cracking it and suggests others be liberal with their use of both wax on the mold before casting, and patience in removing the cement afterward. We might also suggest a strengthening agent like fiber reinforcement. The edges and surface can be sanded to the finish desired and in this case, attaching table legs was easy since the wooden underside of the mold remains on the bottom of the cement.

The neon lighting adds a retro touch to this build. It’s sad to see this technology dying away, so a resurgence of artisanal neon is great in our book. [Elliott] found a Bay Area arts collective called the Crucible which does a lot of art glass education to help him make two hoops of glass tube and fill them with the appropriate gasses. A capacitive touch sensor (once Atmel, now Microchip part) AT42QT2120 (datasheet) monitors the wire coming from the slab and switches the power supply for the tubes using a combination of relay board and Arduino Uno.

We find the prospect of positional sensing in doped cement fascinating. Anyone have ideas for adapting this technique so that a more long and narrow slab could have positional awareness within, say, a few inches? Let us know in the comments.

If you’re looking for other interesting adventures in cement casting, this Thwomp-themed Raspberry Pi proves that what can go wrong will, yet persistence prevails.

9 thoughts on “Touch Sensitive Cement with Just a Dash of Neon

  1. Now that is original! For a better range you need to look at the detection circuit, and consider the work done by Disney if you want to have multiple functions (how cool would that be). For the capacitor plates/grids you need a larger ground grid of stainless steel for electrical characteristics stability over time, nearer the bottom of the slab and then a wire set near the surface, also stainless steel. That should work fine, no extra iron in the concrete mix is required. The advantage of the stainless is that it can be very shallow without ever causing cracks due to rusting and expansion. i.e. you will not get concrete cancer problems if the surface is often wet. A touch sensitive sink or kitchen work area does make sense as you can keep working and still interact with your smart house and mobile phone etc. The circuit just needs to be adaptive so that objects placed on it get ignored after a period of time.

  2. Sectional lighting is what is in mind at a longer table? In ’07 the Black Sparrow opened with a full length curved at the end bar made out of black concrete. It was cast in place in one piece. Nobody will ever bump the table and send a drink to spill into your lap. It is lit with hanging lights, but a sensor and light at each place would be a way of greeting and letting the bartender know to step up.

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