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View Full Version : [Question(s)] Has anyone use QTC pills for gripper sensors



Amp
09-27-2008, 04:54 AM
Hi All

I have come across these effective resistive foam tiles that could be used for robot gripper sensors. Has anyone used these before and could give me some good advice on application?

I am planning on uses these as force detectors on a robot gripper in an array type formation (x y grid). I think I would use a potential divider into an ADC approach. However the range of theses things have a logarithmic decaying resistance from 10Mohms down to a few ohms. This would therefor make a potential divider difficult to optimize the range.

Are there any other typical circuits that could would be good for condensing this range having a logarithmic response to counteract my input source.
I am looking to control this with a micro but external components and specialist chips wouldn't be out of the question. Wondering if some sort of sigma delta design might work nicely ... just speculating.

QTC Pills Product Page:
http://www.technobots.co.uk/acatalog/Online_Catalogue_Pressure_Sensitive_Materials_433. html

Info on basic principals and construction:
http://www.tep.org.uk/millennium_smart_qtc.html

Thanks
Amp

robot maker
09-28-2008, 01:53 AM
looks like a good sensor to try,at a company i work at ,we make scales and we have used before piezo electric cells as a measuring device in one of our scales before they changed over to load cells,i didnt work on the design but i do know about it,i mostly design ,build ,and calibrate high precision in-house final test equipment and pcb board checkers for meters and a/c equipment,
like gauges,phototachometer,freon sniffers and so many more testers
i am going to see if i can get some of the qtc pills to play with on my spare time
the equipment we used to calibrate scales is like anyone else certified weights
i like them because they are small and can be put in xy grid like you said on my robot 5 finger hand i am building,but logarithmic response will be the problem and maybe temperature drift

Amp
10-05-2008, 05:22 AM
After purchasing some QTC pills, I can confirm that they react to pressure change. However they are a rubber like material and therefore don't compress very much at all to make a change. Unfortunately I am looking for a compliant gripper that will distort to an objects shape.

I am now going to look into different conductive foams as well as a capacitive solutions.

However if anyone is looking for a pressure sensitive rubber then QTC pills or sheets may prove a useful source.

Amp

Adrenalynn
10-05-2008, 11:09 AM
How about putting a flex resistor in some known material?

Amp
10-05-2008, 11:31 AM
That sounds like an intriguing idea Adrenalynn. By flex resistor do you mean the resistive sensors stocked at TRC or some other sensor?