Make: Electronics Chp2 Experiment 10

Experiment 10 “Transistor Switching” involves one of the most important electronic component in all of electronics. The transistor. To truly appreciate how the transistor has impacted technology. I highly recommend Googling about the importance of the transistor. As this will hopefully foster a deep appreciation for this piece of technical genius. So many things that you and I own would not exist the way they do today if it weren’t for transistors.

The first circuit in this section that you’ll create is one by which you expose your finger to two jumper leads. The harder you press on the end of the leads the brighter the LED in the circuit becomes. The current flowing through your finger and the positive bus is being amplified by the transistor at its base. That said, this experiment is safe and there is no electrical sensation. Reason being is that a 9v DC power supply is negligible in this scenario.

However, never ever use two hands in a situation like this, or plainly put, don’t ever put yourself in series with a circuit by holding the leads in both hands. You definitely want to avoid current flowing through your body, even a small amount.

*In the video my wife has the two leads touching one finger and is holding the shielded unexposed wire in the other hand. [wpvideo HqST36ZR]

Interestingly enough for the beginner, you’ll observe that the emitter of the transistor is connected to the LED on the board. This provides enough current to flow from the transistor and light the LED. Some of that electricity comes directly from your finger.

More importantly, the major player in this equation is the collector lead  on the transistor, it’s sourced to the positive bus terminal of the board. The base of the transistor is responsible for controlling the current that comes from your finger (in this particular setup). So in a nutshell, we have current flowing into the collector, that current flow is regulated by the base of transistor, and then resulting current from the emitter lights the LED.

During this section of the text, more information about various transistors and the differences between PNP and NPN transistors is reviewed.

Finally, you’ll augment the circuit and add a potentiometer. Under observation you should note that bipolar transistors won’t respond unless the amount of voltage present at the base of the transistor is higher that what’s at the emitter – at least 0.7v to be exact.

Personally, I believe that thus far, this section in addition to the text regarding capacitors is extremely important. Definitely take the time to get the circuits right but more importantly make sure you understand the material and how the components actually work.

Transistors play an extremely important role and it’s worth learning all you can.

Experiment 10 materials:
Bread board
2n2222 Transistor
9volt Battery
470 ohm, 1M resistor
500k Potentiometer

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