Lab VIII & Lab IX:Transistors

This lab was completed in two weeks.
Lab VIII:refers to the first week, which encompassed a continuation of lab vii (can be seen as an edit on lab vii) and part I of the transistor lab.
Lab IX: refers to part 2 of transistor lab, which was completed in the second week.


( i.) Transistors as Diodes
To verify that the transistor behaves like two diodes in series, the lab asked to measure it with a multimeter and verify it had certain resistances. However, this verification was not done using the power supply of the Heathkit. A better way to verify that the transistor behaves like two diodes is by arming a full wave rectification circuit with it and use an alternate power supply (i.e. function generator) and to make sure that the transistor doesn’t fry.

                                      Image I: Function Generator

                                Image II: Full wave rectification circuit using transistor

Resistance measurements:
BE~ 2.40kOhm
BC~ 7.14kOhm
According to the lab manual, the BC resistance should be lower than the BE, which means I probably committed an error while wiring or measuring.

(ii) Transistors as Switches
Wired up the circuit. Skylar pointed out that there are actual switches I could plug into the circuit board.

                                                Image III: Transistors as switches

Image three demonstrates a huuuge misunderstanding on my part. I thought that the 30V was the ONLY power supply on the Heathkit for some reason. So I thought “ok, start out at the power supply, connect to the +5V, so it also has power….”. I’m guessing this is why the green leds started flashing.
Anyway, the voltage measurements:
LED ~4.39V
270ohm resistor ~4.87V
8.2kohm resistor ~3.72V

We were also asked to introduce a 10kohm resistor:

            Image IV : Transistors as switches, extra 10kOhm resistor


Since I didn’t read the directions clearly, I thought we were continuing the lab from the lab manual. Hence, I started arming this circuit:

Image V: A circuit we weren’t supposed to arm


After I had found out I  was arming the wrong circuit, I thought I would just continue with the  lab using this circuit and connecting the DAQ card to the LED. However, the fact that the +5V was a power supply on its own was still misunderstood by me and I committed the same error as in Part I-ii. The Heathkit began to smoke, and Anthony checked if I had broken the Heathkit by wiring the LED by itself. It appeared to be working.

                          Image VI: The majority of the circuit (left), wiring the LED separately to check if the Heathkit was still working (right)

I decided to abandon this circuit completely as well as abandon the Heathkit. Skylar suggested to use the protoboard and the DAQ card as the power supply. This worked out really nicely, since the DAQ card provides +5V, has two grounds and wiring is a little smoother on the protoboard.

Image VII: Right circuit using protoboard and DAQ card

                             Image VIII: DAQ card terminals

Compare to:

                                 Image IX: DAQ card terminals

After this was set up and ready to go, I examined the VI PhD. Koch created:

                                Image X: Front Panel

                                         Image XI: Back Panel

The gist of the VI was to act as the switch of the circuit. Notice how one of the switches is on in image X? This means that the LED in image VII was on, which is really neat. PhD. Koch explained that the “binary representation” and the “decimal representation” both represent the same value. It seems pretty obvious reading it now on the front panel, but since I’m not familiar with binary numbers, it wasn’t obvious at first. The board number is the number acquired from the DAQ card via instacal testing, and PortNum was the number of the portal on the DAQ card, which was 33 aka FIRSTPORTB aka PortB1.
Problems and Solutions

1.  DAQ card testing: while testing it via instacal I tested the analog, not digital. This was wrong because we’re using the VI to control the LED, which is digital. So, I retested the digital and plugged the wires into the digital side.

Since the forked folder from Part I was altered for Part II, we couldn’t just refork it.
To do this, I referenced Brian’s notebook (we were supposed to have done this in lab 6/7) :
However I ran into some problems.
PhD. Koch explained that I had to re-adjust the remote from upstream to origin. Also, not to include https when commanding git remote add upstream git: copyandpastethelinkoftherepositorybutwithoutthehttps