Bare Conductive Touch Board Starter Kit review

By Ben Everard. Posted over 6 years ago.

Bare Conductive makes conductive paint and the bits and pieces needed to make use of this paint. Its touch board is an Arduino-compatible microcontroller, with an added set of touch-sensitive pins. These pins can work with the conductive paint to turn almost anything into a touch sensor. Just place the touch board flat on a surface and paint directly from the touch pins to add touch sensitivity to almost any build. Of course, you can use the paint to wire up all sorts of circuits.

The technical specifications of the paint claim that the resistance of a 50 micron layer of paint is 55 ohms for a square. This might seem slightly odd to people working with things that have a different resistance for different lengths (such as wires), but a square sheet of material will have the same resistance regardless of how large it is. Basically, this is because as you make something wider, you decrease this resistance, but as you make something longer, you increase it, and in a square, these exactly cancel out.

Don’t be so square

Of course, you rarely need to work in squares, so we measured the resistance of traces from the paint tube. We found them between about 60 and 150 ohms per centimetre, depending on how thick a line of paint was used (as the paint is quite viscous, it’s easy to create a thick bead). This is slightly higher than silver-based conductive paints, but these are generally more expensive. At this resistance, you can create a capacitive touch sensor or light an LED with a moderately long line, but if you’re planning on doing something that requires more current (such as running a motor), you may run into problems.

In the Touch Board Starter Kit, you get a touch board, a tube of paint (10 ml), a jar of paint (50 ml), a speaker, some crocodile clips and some stencils, cut-outs, and other bits and bobs to join it all together.

Touchy feely

The touch board has a micro SD card for storing sounds and a 3.5 mm audio jack for playing them, (such as through the included speaker). When you first power up the board, it has a brief audio guide loaded that you can page through by touching the input pins in order. It’s easy to change the sounds to make different noises when things are touched. The touch inputs are in large pads at the side of the board, so you can either use crocodile clips, or lay the flat-bottomed board on paper and use the conductive paint to create traces directly from the board.

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Slightly unusually for an electronics kit, there aren’t any components – no LEDs, buttons, motors, or anything else. It’s not actually that straightforward to wire bits like this up to the touch board. Although it does have some GPIOs exposed, they’re not on the main connectors and you’d have to solder onto them to be able to access them. This wouldn’t be a particular problem, except that the board needs to have nothing protruding from the base if you want to be able to connect directly to the paint, (though you can still use crocodile clips if there are headers soldered on). Bare Conductive no doubt has its reasons for this layout, but we can’t help but feel that the kit could have a lot more uses if just a few GPIOs were exposed in the same way as the touch pins.

Part of the problem may be that the resistance of the paint traces means that you need to be a little careful with voltages to get things to work properly, because the resistance of the paint traces is so much higher than metal wires. We found that we needed at least five or six volts to make LED circuits reliable. This could lead to confusion among beginners when circuits didn’t work.

Going it alone

Of course, you don’t have to use the touch board; you can just use the conductive paint (this is sold separately at £6 for a 10 ml tube, or £18 for a 50 ml jar). If you’ve got a steady hand, we found this worked well with 1206 SMD surface-mount LEDs, as they could be placed (using tweezers) in a gap in a trace, and the paint had enough adhesion to hold them in place when it dried. The paint also works well with through-hole components, and Bare Conductive also sells a Glowing House kit for £22, which includes a fold-out house, and the bits you need to light it up using conductive ink traces.

The Bare Conductive Touch Board Starter Kit does one thing really well – playing sounds when a painted pattern is touched. There is the capability to go beyond this and try more things out, but it’s a bit of a step up between the basic usage and the more advanced options.

If you’re more interested in playing around with paper-based circuits, then Bare Conductive paint can work well (with a caveat about the resistance), and you can get started with this without the touch board.