Conductive lycra stretch sensor

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi,

i'm trying out using conductive lycra or 'electrolycra'. Aparrently this should change resistance as it stretches but I don't seem to be able to get this effect. Does anyone have any tips about how to get this to work?

many thanks,

Chris

2

How are you measuring the resistance?

3

Hi,

i'm using a setup the same as here,

http://wiring.org.co/learning/examples/forceresistor.html

using analog input 0 of the Arduino, and with the electrolycra where the FSR is in the diagram, connected with crocodile clips.

Chris

4

OK, so you're comparing the lycra with a 1k Ohm resistor. Do you know the approximate resistance of the lycra? Can you measure it with a multimeter? I'm just wondering if the range of variation is too small to detect with a 1k load.

5

The spec of the material says:-

Resistance = 5 [ch937] per 100mm. Increasing to 20 [ch937] when stretched to 150mm in one axis but dropping to 2.5 [ch937] when stretched at 90ยบ to this.

So you are using a 1K resistor in the bottom so you will not see any change in reading as the resistance is very small compared with the 1K.

The simple answer would be to use a 20R resistor in place of the 1K BUT this is way too small and would cause too much current to flow.

Therefore you will have to consider some other way of conditioning the signal before you feed it into the arduino. The best bet would be to use a bridge circuit with extra resistors top and bottom feeding into an op-amp before going to the analogue input.