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Guitar String Sensors
I will go through the process of making a guitar string physical touch sensor. These are a great type of sensor, really useful for your BEAM robot. It is really easy, you will need:
- 20cm Solid Core wire
- Hot glue gun (can be done without this)
- Metal guitar string, I have used a Low E string, or an A string.
- Solder, and a small diameter object to create a coil.
- Optional - Heat shrink
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The first step is to take a long piece of solid core wire. I have used 20cm. |
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Now bare 5cm of the wire at one end. On the opposite end, bare enough wire to solder to (this will be the end which connects into your own circuit). |
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Now take this wire and coil it around a small diameter, I used a fine paintbrush handle, anything smaller than a pencil should do it, but not too small (it must fit a guitar string in, and have room to not have constant contact!). |
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Now take your guitar string and solder some wire to one end. This piece of wire will be the other connector into your circuit, so make it as long as you feel appropriate for our need. |
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Now solder some wire to the end of your coil, ready to put into your circuit. We are soldering the connection wires on now because we are about to hot glue the guitar string into the coil and we don't want it to re-melt.
You may notice that I have used some heat shrink to cover the solder join, this ensures the sensor will not be shorted when the guitar string is inserted into the coil. |
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Now place the guitar string inside the coil, the two soldered ends of the coil and guitar string should be in the same place. We will now glue the guitar string into position, I use hot glue for this as it sets fast but gives me enough time to make sure the position is right. |
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The guitar string needs to be exactly central within the coil, otherwsie it will be biased to one direction (you may well wish to achieve this anyway).
You could also achieve this by wrapping something around the end of the guitar string to hold it away from the edges, perhaps by gluing a rubber band around it, or by wrapping wire around it. |
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You now have a complete sensor, the final thing is to adjust the sensitivity by tightening the bare coil a tthe end. I do this with needle nose pliars, play around until it is sensitive enough for your application. |
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