Diodes

 Today we worked on diodes. At first we looked at voltage drops across diodes and LEDs with our multimeters. We also looked at identifying the Anode/Cathode without using a multimeter. On a diode, there is a silver stripe on the cathode end, and on a LED there is a flat edge.

Today we started to use bread board for component analysis. First up we measured and calculated current and voltage across a diode in a circuit. I wired up a simple circuit containing a 1K resistor, a 1N4007 Diode, and a 5v power supply. I then calculated what current should be running through the circuit using the formula I=(Vs-Vd)/R. (5v-.7v)/1000ohms means that the current should be approx. 4.3mA with a steady supply voltage. My measurement with the multimeter showed 4.4mA which was expected as my supply voltage was slightly higher than 5v. Next we calculated voltage drop. From prior advice from my tutor, i knew that the voltage drop across the diode should be .6-.7v approx. over each diode. My multimeter proved my teacher correct, as the voltage needed to work it was indeed .64v.

I then replaced the diode with a LED and did the same tests. The voltage drop was significantly higher(1.8v), i believe this was because it is a bulb aswell as a diode. I calculated that the current should be similiar to 3.8mA. It was 3.2mA.

My next experiment on diodes was on a Zener diode. I created a compound circuit with a resistor and a Zener Diode in parallel, and a resistor in series. Then i calculated the value of Vz (Voltage drop across the Zener). Vz=4.97v when Vs=10v, and 5.1v when Vs=15v. This shows that if the voltage increases, the Zener Diode will stabilize it by raising its voltage drop. This is why a Zener diode is helpful as a voltage stabilizer in a circuit.

My final experiment involved putting diodes ( A Zener in reverse bias, and Rectifying in forward bias) in series with a resistor. I ran ten volts through the circuit, and my results were: Vz=4.6v, Vd=.6v, Vr=4.7v. I then adjusted Vs to 15v, and re-measures my voltage drops. I got Vz=4.8v, Vd=.7v, Vr=9.5v. This shows that once the diodes have reach their breakthrough voltage, they do not require any more voltage to operate, thus the resistor will consume what voltage is left.