Project H.A.N.D. – P.o.C. Finger movement

Hi all,

One of the main items I wanted to include in the h.a.n.d. project was the ability to track the position of the fingers.
So I should be able to track the amount of how I bend my fingers. 

So after some checking on the internet the conclusion was that bend/flex sensors are the way to go. I found several 2.2″ versions on Ali and Ebay. However, they are still about 8 euro’s a piece cheapest. And that times 5 will majorly increase the overall costs of the project. So another solution must be found.

Once again google was my best friend. After a night of searching and reading there are two main solution to go for.
1. Sensor based upon resistance.
2. Sensor based upon light.

For both options there are several ways to go. I initially looked into the optical solution. However that includes creating a tube with a light on one side and an LDR on the other. 
First of all the tube to connect the two together must be sturdy and flexible at the same time. So when I bend my fingers the tube will not be in the way of my finger movement but also holds its shape to ensure the light can reach the sensor in the required gradients.
That proved to be harder than expected. The lot of the tubes I could get my hands on were either to flexible and closing themselves up after around 45 degrees of bend. And all the others were just to big for the project I’m working on. Maybe within the Steam Punk setting I have room for doing something with that but if I want it to be nice sleek and modern.. no way.
Second issue I encountered is that this does need power to be driven. Five fingers means five LED’s. Five LED’s times 20mA for forwarding voltage means a bigger battery. And everything must be as power efficient as possible as I want to use a small 3.7v Li-Po in the end. So this option goes back into the closed as it currently takes to much time to find a proper solution.

So the next option was based upon resistance.
Some small investigation showed that the ones you can buy are based upon two layers of copper with a pressure resistance material between them. Other options are based upon fabric with conductive capabilities.
While being a great solution to use fabrics, they are quite expensive. Especially when you only use small amounts. And the amount of wire and fabric needed for 5 fingers…. So that is for now not really an option. The goals is to include as much as possible as cheap as possible and get it working. Fine tuning and better quality materials are something for later on.
So back to the original sensors which can be bought online.
The major amount of information found on the web showed that the sensors can be home build using scotch tape, copper wire and with a material called Velostat. Velostat is a conductive carbon injected plastic (or something like that). Those old fashioned black computer part bags sort of say. I got a sheet which is around the size of a A4 for about 7 euro’s including shipping. Looking at the tutorials I should be able to make at least 40. In other words… Cheap.. Enough to test with and enough information on the web to be used as guidance.

So by now I have tested several setups based upon the basic concept. At the same time I must ensure that the sensor itself stays small enough to be included in the glove above the fingers without disturbing the visual look of the glove.

But more on that in the next post. I then show some of the test sensors and they way they were build.

Till then..

 

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