Experiment 2: Introduction to Biasing

Introduction

     Determine the resistance required for the LEDs to perform under its maximum load conditions, (biasing).

     Test the circuit and obtain data that either matches or is different from our predictions.

     Calculate efficiency and power.

     

Procedure

     We first calculate by using Ohms law and KVL for the circuit.

Also, R_LED1 = 220 Ohm R_LED2 = 100 Ohm

The designed values of the resistors are not exactly the 

values we need, so we use the values R1 = 220 Ohm and R2 = 470 Ohm.

The final setup of the circuit.

The red and green cables are used to connect the ammeter and potentiometer.

We recorded the data based on these specifications.

The following questions were calculated using the data chart on picture 4 and picture 2.

9V battery is just 0.2A-hr. With both LEDs in the circuit (Fig 2), how long can the circuit

 operate before the battery voltage goes too low?

Calculating the percent error

I_A = I_1 + I_2 (KCL bottom node)

The theoretical value and actual value varied by -17.77%.

Reasoning to this might be that the LED's operating voltage might have been erroneous and that the battery might be current or voltage dependent.

Calculating power efficiency

E = 3.6 / V_B

E = 3.6/9

Power efficiency is calculated to be 41.3%

If the battery is 6V and the current through the LEDs must be specific, then the power efficiency is
1.5 times greater than when the 9V battery was connected.
E = 3.6 / 6

Compared to 9V, the efficiency is increased.

Power efficiency is found to be inversely proportional to voltage, and the maximum efficiency one could get is when the battery gives about 3.6V to the circuit. Any less would mean that the current requirements will be impossible to obtain.

Conclusion.

     The data we have obtained from the circuit matches our theoretical within reasonable uncertainty.
     The circuit is has the most power efficiency when the voltage is at the minimum requirement to sustain the needed current.