Interfacing Lilypad with very low resistances

Forum 2005-2010 (read only) Hardware Interfacing
1

I'm working on a project at the moment which involves using conductive lycra to influence a Max/MSP patch and I'm currently stuck.

The issue is that the lycra has very low resistance (~10 Ohms) so the only way to get a measurable result with a standard voltage dividing circuit is by putting it in series with a similarly low resistor. Obviously this causes too much current to flow, so I was wondering if there was some way to get around this?

I was thinking if I put another larger resistor in series with the lycra and low value resistor it would limit the current and then I could add some kind of buffer circuit to boost the signal back up to a voltage that would be suitable for the analogue ins on the lilypad. Does this make sense? Does anyone have any pointers of what I should be looking for? I've had a good search around and it looks like nobody's had a similar problem, at least using the same terms I've been searching for. :slight_smile:

Thanks in advance for any help you could give me.

2

Measuring low resistance values is tricky. Using a larger series resistor limits the swing you can get out of it.
One way to do it is to put a small current through it and measures the voltage. The current needs to be small and so the voltage is small so it will require amplifiers.

Another method is to use the resistance to control the frequency of an oscillator and then measure the frequency.