While these components are not as used as much as they used to be, its important we understand them for the occasions when we do come across them.
Youtube video, suitable whether of not you have the board with you.
See board images.
Tutorial guide for when you have the board with you.
Zener Diodes can be used to create a regulated voltage – so what’s that? Well, it’s when we want a specific voltage to for electronic components and we either don’t know the supply voltage or it’s more than we want. A zener diode will change its resistance to try and ensure it always has the same voltage across it. Ensure the two LED switches are in the down position and move the rotary switch to first position next to OFF. You will see the two digital meters turn on. The top one is showing the supply voltage and current coming from the battery. It shows there is a current flowing through the resistor and the zener diode. The zener will control the flow to try and ensure that there is a specific voltage across it. Note the current shown by the meter. The bottom meter is showing the voltage across the zener and the current flowing through the two LED bulbs - this will be zero at the moment as the bulbs are not switched on. Note the voltage, it's just under 3 volts. To hold this voltage there is a current running through the resistor and the zener.
Now switch on one of the LED lights. You will notice that the current on this bottom meter has changed to about 30 milliamps but the voltage has not changed significantly. Turning on the second light will increase the current again but not really change the voltage. The current flowing through the zener is the difference between the two meters. Changing the rotary to position to the next two positions will increase the supply voltage because more batteries are being used, but you will see that the voltage across the zener doesn’t really change.
Note that that the zener is valued at 3.3V but in practise the voltage we will measure across it will be lower – here about half a volt lower.
Zener diodes are very useful gadgets but they can waste a lot of power. If you touch the zener or the resistor you will find that after a while it will get hot because of the current. If the current required by the device needing the specific voltage is low its fine, but zener didoes are not used when a lot of power is needed.
You can calculate the power being wasted by the difference in power between the two meters. The power (measured in watts) being the voltage (in volts) multiplied by the current (in amps).