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View Full Version : flexi force circuit doesnt work



mspmarkus
12-11-2011, 10:01 AM
Hi, i am new to this site, so first of all great work!

now my question:
i am working on a sensor glove and using flexi force sensors.
i am using the secuit recomended by tecscan but it "kind of not works".

i used a poti as Rf and turned it to 110k. but still i get a 2,14V at the exit of the opamp. i think i should be near 0. Is that true?
Instead of the 5 V at the opamp i use 3,3 and instead of the -5V i use -3,3.

does anyone know where my mistake is??
http://www.electronicspoint.com/attachments/1191d1289445075-flexiforce-drive-circuit-flexi-circuit-new.jpg

ruscanskyd
12-13-2011, 12:37 PM
It does make sense that Vout with no load applied to the sensor should be close to zero. There are a couple of things that you should test to help determine the issue. The first is to replace the sensor with a know resistor value to see if the op amp is bad or the circuit is wired incorrectly. If the measured voltage is close to the calculated resistance, then the circuit is not the issue. The second thing is to measure the resistance of the sensor with no load, and then with a load applied to see if there is a large change in resistance.

What is the force range of the sensor you are using? Are you using the MCP6004, or a different op amp? What are you using for your supply voltage?