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Videos / Makey Makey - How to Setup Capacitive Touch

Source: core-electronics.com.au

Capacitive touch is our favorite config for Makey Makey - it's simple and enables a world of new project ideas. In this video we show you how to set it up, and why it's generally awesome :) One of the key issues is sensitivity - which Sam explains and is covered in this tutorial

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Hi guys, it’s Sam here from Core Electronics and today we’re going to be taking a look at reprogramming  our Makey Makey to work with capacitive touch.  So in our last tutorial we were taking a look at Resistive touch and how that worked, needing to create a circuit from our input pad to our earth pad in order for something to happen. This is great but as we were talking about there’s a few drawbacks, you know intuitively we want to touch something with our hand like that and have it work. Thats the way our computers, our phones, everything around us works. So it can be a bit of a drawback having to hold on to the ground pin while you do things. Now fortunately this is where capacitive touch comes in, the actual principle behind it is a little bit complex so I’ll leave you to do some reading on that but the basic idea is that the microcontroller on board is measuring the capacitance on the input pin versus our body’s natural capacitance, so what ever is touching the pin when we touch the jumper lead attached. So it’s working on that, it’s timing specific and it’s quite complicated but we’re going to break it down and have a look at how we can actually reprogram our Makey Makey to work with capacitive touch instead of the standard resistive touch. We won’t be needing this earth cable so we can get rid of that, that’s gone.

If you scroll down we’re going to be using the Makey Makey with the Arduino IDE. The Arduino platform, if you haven’t used it before then check out some of our Arduino tutorials for setting that up and downloading the IDE because we won’t be covering that today. Today we’ll just be covering how to get it up and running with the Makey Makey.

The Makey Makey isn’t compatible with Arduino straight out of the box you need to download the Makey Makey libraries and down in the tutorial you can see a link to the article over at SparkFun so we’re going to go ahead and open that up and take a look at that and you can see there is the spark fun guide. There’s a few downloads so if you walk through this and read it really really carefully, you’ve just got to download a file and it’ll tell you where to put it, what to do with it, and after that we can go ahead and use it in the Arduino IDE. So go and look at that and once you’ve got that sorted out you should be seeing it show up in your boards list in the Arduino IDE. If not then go back and follow the steps and get that going so we can move on.

We’ve got it going in the Arduino IDE, I’ve programmed this board to work with capacitive touch already and the code is actually taken from somewhere else on the internet, a fantastic guy by the name of Eric Rosenbaum (I think that is how it’s pronounced). I originally uploaded this code and I made a few tweaks to just work a little bit nicer with external things like large fruit that have quite a lot of capacitance to them anyway. I was finding some of the sensitivity readings were a bit off. Fortunately it’s super easy to adjust the sensitivity and you can see here that you can actually adjust the threshold and the larger the number its going to change the capacitance. Obviously to make it less sensitive the smaller the number the more sensitive it’s going to be. We can also re-map the key array, so we can change what pads on the keys are going to trigger and what an actual keystroke.

We’ve got this plugged in and turned on and now with resistive touch we would have had to be connecting two of these pads up to make a circuit, now it will still work that way if you go back and put the original firmware on it. Its not like you’ve messed up your board or anything , the original firmware is available at MakeyMakey.com and spark fun in that guide. So you can go ahead and reprogram it, that is not a problem.  We are actually going to have a look at using things like fruit and world objects to connect up and we don’t have to use the earth pad. So we’ll just go ahead and connect these up and I’ve actually got these pre-programmed to work as a keyboard so I’ve had to re-program the arrow keys and the space bar to change what they do so they don’t actually correspond to what is written on here anymore but you can change that to do what ever you like.  So now as you can see I’ve just clicked on the search bar and I’m not holding any external ground wire and I tap on the fruit and it’s bringing up and it’s typing things in and I can also tap directly on to the board as well but typing with fruit is much much cooler. So as you can see the sensitivity is really good and if you hold it down it works as expected, with some capacitive touch you can find it actually senses your hand, it’s that sensitive because of the high capacitance but we’ve dropped the sensitivity down so it works really really well with this kind of stuff - large fruit, small fruit, the lead pencil drawings we were talking about, it’s going to work. You can simply type in any value you want using capacitive touch, what’s handier than capacitive touch, it’s really intuitive and works the way you would expect it to.

I encourage you to go ahead and play with that and find something cool that you can make with it. You can remap the keystrokes that it sends to the computer and do whatever you like and make some awesome projects and show us. We’ve got a project section on our website and we’d love to check them out and you can inspire other makers and inventors.

That’s all for today guys, I’m Sam, thank you for watching and remember to check out some of our other fantastic Makey Makey tutorials - seeya :-)