9.2: Force Sensor

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Let’s replace the potentiometer with a sensor. For this exercise we shall use an FSR or force sensing resistor. An FSR is a two terminal device usually in the form of a flat film, the resistance of which depends on the applied force (FSR 400 series data sheet and integration guide). With no applied force the resistance is very high, usually much greater than one megohm. With full force applied (such as a hard squeeze of the fingers) the resistance may drop to as little as 100 \(\Omega\). Remove the pot and wire one lead of the FSR to the +5V header pin and the other end to a 10 k\(\Omega\) resistor. The connection point between the resistor and FSR should be wired to analog pin A0 while the free end of the resistor should be connected to ground. This is nothing more than a voltage divider, one leg of which is a force-dependent resistance. As force is applied, the resistance drops and therefore the connection point voltage will rise. Do not change the code. Simply note how the values in the Serial Monitor change as force is applied to the FSR: the greater the force, the greater the value. Finally, swap the positions of the resistor and FSR. Increasing force should now result in decreasing values in the Serial Monitor. Leave the FSR in this new position for the remainder of this exercise.