STATEMENT OF THE PROBLEM:
To construct a portable mobile charger using pressure transducer. When pressure is applied on the object, its resistance changes. This change in resistance can be used to generate voltage using wheatstone bridge network.
The pressure sensor used is strain gauge. It is connected to one arm of the wheatstone network whose other arms have fixed resistances. When no pressure is applied on the strain gauge, the wheatstone bridge is calibrated to give zero output. When pressure is applied, there is a change in the resistance of the strain gauge. Due to this, imbalance is created in the wheatstone network.
The output taken from the wheatstone network is given to an operational amplifier which amplifies the output. An operational amplifier is used as it has high open loop gain. Using feedback, the output is stabilized. This final output is taken to charge the mobile phone.