Report on the Parts of the Sensor Steering Circuit of the System

5 pages
1162 words
Carnegie Mellon University
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Operational amplifier

The sensor circuit subsystem uses the operational amplifier which has two inputs and one output listed as inverting input, noninverting input and output. The terminals in its design are four which includes a ground. The ground signal terminal provides a reference point for three others. When there is no risk of misperception, the ground is usually omitted in the amplifier symbol, and the terminal voltage is indicated. This is a flexible amplifying device that was originally used in analog computers to perform linear mathematical operations which include addition, subtraction, differentiation or integration. The operational amplifier is a direct coupled amplifier with a low level of inherent noise and high gain, capable of constant process in a close-feedback loop. The direct flow of the signal in the amplifier is from the input going to the output.

The output of the amplifier depends on the comparison of the two inputs functions performed which are the inverting input and a noninverting input. These amplifiers have feedbacks, but others do not provide that feedback. The feedback network which is always represented by the cross hatched area and consist of passive and active electronic and electromechanical components is termed as nodes which provide the connection to the signal terminal of the operational amplifier, signal source and load. If the amplifier does not have feedback, then it will act as a comparator.

When the output is high, it means that the inverting input is lower than the non-inventing saturating itself towards the positive voltage. On the other hand, When the output is low, it means that the inverting input is higher than the non-inventing saturating itself towards the negative voltage.

A simple operational amplifier always has a current flowing into its input which results in an infinite input impedance. Many of the operations amplifiers have their feedback from the output back into one of the input pins, and when this occurs, the voltage will be adjusted trying to bring the two inputs close together creating a more of a closed loop that tries to bring the error occurring to zero. A noninverting is when the feedback is being fed back using the noninverting input pin which is known as a positive feedback. In this case, the input voltage is the inverting pin. An inverting amplifier is when the feedback is fed from the output back into the inverting input pin, this can be known as negative feedback. In this case, the non-inverting pin is the input voltage.

Feedback occurs as a result of the comparison of the output, and that of the input referred to as a gain. If the comparison is equal to both output and input, then the gains are one but are the output voltage is ten times that of the input then gain will be rated as 10. When the inputs are all equal, then the gain is zero. The resistor in the feedback, in this case, is used in the circuit to adjust the voltage of the input to give the result at the output. As it can be seen, there is negative feedback from the output back into the inverting (-) pin. The non-inverting (+) pin is the Vin. R1 in the feedback is connected to the ground; it is also in series with R2 coming from Vout.


A diode is an electronic device that is designed only to allow the current to flow in one direction which is the forward direction. It does not allow the current to flow in the opposite direction. The component of the diode includes the cathode which is the negative end and anode being the positive end. When the voltage across the diode is negative, the diode will be put in a reverse bias making it not to allow any current to flow through it acting as an open circuit. One the other hand when the voltage across is not negative, then it switches to forward bias allowing the diode to start conducting electricity making the current to flow through it thus acting as a short circuit.

The discussion will look at the Zener and Schottky diode. Zener diodes are constructed to take advantage of reverse current. High reverse biased voltages applied to a diode may create a high reverse current which generates excessive heat and causes a diode to break down. This applied reverse voltage I called the peak reverse voltage of breakdown voltage. At this instance, the Zener diode is connected to operate in the reverse biased mode. It is designed to operate on those voltages that exceed the breakdown voltage. The Zener diodes have a breakdown voltage of 5 volts and also a positive Zener temperature coefficient meaning that the breakdown voltage increases as the temperature increases.

A Schottky diode is also useful and has a smaller forward voltage drop of 0.4 volts. It's efficient is seen in blocking reverse current flow. Depending on the amount of current flowing through it, the forward voltage of the diode can change. The advantage of this diode is that it can produce a voltage rectification and also it can obtain a higher frequency because it has a fast switching speed


The last part of the sensor steering circuit of the system is the rectifiers. The primary goal of this rectifiers is to change the output of specific signals converting the direct current (DC) from alternating current (AC). The Ac signals flow in all direction, but the DC signals flow in a constant direction. There are two type of rectification filters namely the full wave rectification and half wave rectification but in this experiment, the discussion will on the half wave rectifier.

For the purpose of rectifying the signals, capacitors, diodes, and resistors are used. To give the desired signal for the experiment, the first process of rectification uses a Schottky diode, the resistor, Zener diode and finally the capacitor finish the process. A filtering portion of the rectification is also added consisting of a resistor, Zener diode and a capacitor used to get a DC signal. At the output of the Schottky diode, a RC circuit is placed for the capacitor to charge and discharge causing a ripple that rectifies the half wave signal into ripple signal. For precision, the ripples are preferred to be below 5 percent whereby the resistor and capacitor have to perform to give an appropriate ripple for the steering sensor.

DC inductor voltage to microcontroller

The inductor produce the 1A, 20 kHz signal reading on whether the car is on track from the wire. After the accomplishment of the inductor in the filtering and rectification process the controller receives the DC voltage to the analog input. This inform the controller that the DC voltage s of the inductors are reading from the track. An mbed program was created in which a proportional plus bias controller was implemented based on the error between the two inductor signals. The controller then creates a suitable duty cycle that will be sent to the servo system.


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