Page 768 - Mechatronics with Experiments

754 MECHATRONICS
7. In the RC circuit, measure the step response: input voltage is V (t) which can be
s
connected to a function generator to generate a square (or rectangular) wave signal
instead of using battery and mechanical switch and output is the voltage across the
capacitor. Measure the time constant of the response, : the time duration during
which output voltage reaches 63% of its steady-state value. Note = R ⋅ C for this
RC circuit input–output transfer function.
8. Do the same for the RL circuit for step response. This time measure the voltage across
L to measure the time constant. Note = L∕R s for the RL circuit input–output transfer
function.
9. Experiment with different values of the R, L, C in the RC and RL circuit and
measure results in terms of input voltage, output voltage, and current. Verify these
®
®
measurements with numerical simulations in MATLAB /Simulink .
Note that the mechanical switch can be removed from the circuit. Then, V supply
s
voltage and ground can be connected to the function generator which is configured to
generate a square (or rectangular) wave signal. This approach may be easier to capture the
step response of the input–output relationships in the RC and RL circuit.

11.2 EXPERIMENT 2: TRANSISTOR OPERATION:
ON/OFF MODE AND LINEAR MODE OF OPERATION

Objectives

1. Understand operating principles of a NPN type BJP transistor.
2. Design and build a circuit involving a NPN type BJP transistor in common emitter
configuration.
3. Experimentally determine the ON/OFF mode and linear mode of operation, and
measure the relevant voltages.

Components

Item Quantity Part No. Supplier
Resistors as calculated, 1 81832 Jameco Electronics (www.jameco.com)
Assortment Kit
BJP transistor, NPN type 1 38359PS Jameco Electronics (www.jameco.com)
Breadboard 1 20722 Jameco Electronics (www.jameco.com)
Set of connection wires 1 set 20079 Jameco Electronics (www.jameco.com)

Theory
The transistor is like an “electron valve.” It is the electrical analogy of the hydraulic valve.
A hydraulic valve regulates the flow of fluid: it can be fully closed, fully open, or partially
open. Rate of fluid flow is a function of the hydraulic pressure across the valve and the
amount of opening of the valve. A transistor is an electrical valve. It regulates the flow of
electrons. It can be fully OFF, fully ON, or partially ON. If a transistor is operated only in
either fully ON or fully OFF mode, we call it ON/OFF mode operation. In the OFF mode,
transistor state is called the cutoff state. In the fully ON mode, it is called the saturation state.
In between them, it operates proportional to the base current and is said to be in linear mode.