## Saturday, December 11, 2010

### Potential Divider and Transducers

Potential Divider

The "Potential Divider" is a line of resistors in series that are used to give different voltages in parts of an electronic circuit. The voltages can either be set to fixed values or be adjustable. As the name says, it divides the "potential" (voltage) into different amounts.

Fixed Potential Divider.

The Supply voltage is 9V
The two resistors in series have equal values and they divide the supply voltage into two equal parts allowing a voltage of 4.5V to be supplied to another part of the circuit.Three resistors of equal value would divide the supply voltage into three, allowing 3V, 6V and 9V to be used by the rest of the circuit.

Potential dividers are often placed directly after the supply source to allow different voltages to be feed directly to different parts of the circuit. In the Op-Amp comparator circuit below, the potential divider network of two 10K resistors give a fixed voltage on Pin 3 equal to half the supply voltage.

To find the values of resistors in a Potential Divider network to obtain a particular output value, use the following method.

Calculations

Knowing the values of the resistors, it is simple to calculate the Output Voltage using the following formula.

To find the values of resistors in a Potential Divider network to obtain a particular output value, use the following method.

Transducers

A transducer is an electric or electronic device that converts one type of energy to another. The conversion can be to/from electrical, electro-mechanical, electromagnetic, photonic, photovoltaic, or any other form of energy. While the term transducer commonly implies use as a sensor/detector, any device which converts energy can be considered a transducer.

Input and output Transducers

Input Transducers convert a quantity to an electrical signal (voltage) or to resistance (which can be converted to voltage). Input transducers are also called sensors.

LDR

Examples:

• LDR converts brightness (of light) to resistance.
• Thermistor converts temperature to resistance.
• Microphone converts sound to voltage.
• Variable resistor converts position (angle) to resistance.

Output Transducers convert an electrical signal to another quantity

Loudspeaker

Examples:

• Lamp converts electricity to light.
• LED converts electricity to light.
• Loudspeaker converts electricity to sound.
• Motor converts electricity to motion.
• Heater converts electricity to heat.

Most input transducers (sensors) vary their resistance and this can be used directly in some circuits but it is usually converted to an electrical signal in the form of a voltage.

The voltage signal can be fed to other parts of the circuit, such as the input to an IC or a transistor switch.

The conversion of varying resistance to varying voltage is performed by a simple voltage divider.

Hence, the calculation of voltage is done through the
potential divider formula (for both input and output transducers).