Electronics Lab 3

Experiment

This lab was all about oscilloscopes, and learning how to calibrate them to get effective voltage readings. I found this process to be pretty intuitive, and it wasn't too difficult to figure out the Volt/Div and Rate values needed to get a clear signal. As for the actual results, my data really doesn't show anything definitive.

Here is a schematic for the circuit we used. I couldn't find an audio jack representation in Circuit Lab so I just used a voltage source and a speaker as substitutes.

Here is my data for the experiment. As you can see, the voltage drops created by running audio through the circuit were fairly negligible, and there isn't a definitive pattern apparent in these results. I know there is a drop in voltage occurring as the audio is passed through the circuit, just because of the resistance present, and this drop is shown in most of the frequencies. 

When I ran pink noise through the circuit, the signal was much quieter, and the low end was basically non-existent when compared to the unaltered signal. The same was true with white noise, though the higher frequencies were louder than pink noise, but that's due to the more evenly weighted nature of pink noise.

Final Project

I'm fairly certain I want to do something with the Reso-Drum, which seems fairly inexpensive to produce. The most expensive parts are the electromechanical transducers, which are about $20 each. However, since the tutorial I found uses a max patch as the sound source, I need to figure out some way to create a signal source that isn't so reliant on the computer. I might make my own max patch or something like that, but since this is analog electronics class, I assume I should try to make an oscillator type device as well. 

Electronics Lab Report 2

Experiments

This is the first circuit we made in class

It had 4 1kOhm resistors along its path, as well as 2 polarized capacitors. The audio signal was fairly clear and had a little bit of static. The volume on my phone was about 3/4 way up for the signal to be audible.

This is the second circuit I built for the experiment. It only consisted of two wires running from one audio jack to the other. The audio signal was much stronger, and I only had to turn up the signal a tiny bit for it to become audible. The audio was also a bit clearer than the circuit above. The capacitors in the picture aren't part of the circuit.

Sorry about the orientation of this photo. I couldn't figure out a way to make it horizontal. This is the circuit I built with 4 1 kOhm resistors in between the audio jacks and the wires. This significantly cut the volume of the signal. I had to turn the signal back to about 3/4 of the way up on my phone for it to be audible. Audio quality, when turned up, was about the same, but with perhaps a bit more static.

This circuit is similar to the last circuit, but it uses a potentiometer instead of one of the regular resistors. With the volume all the way up on my phone, I had to turn the potentiometer to about 3/4 of it's full rotation to get an audible signal. Basicallly acted as a volume knob.

This is the circuit with 4 1 kOhm resistors and two 1 microFarad capacitors. The difference in audio quality was definitely noticeable, as the lower frequencies were significantly quieter. I also tried the same circuit with 0.1 microFarad capacitors and 0.01 microFarad capacitors. As the capacitance decreased, the frequency at which the audio signal seemed to cut off increased. For instance, with 0.01 microFarad capacitors, only the higher frequencies reached the audio jack.

This is the circuit with the signal wired both directly to the audio jack, and to a capacitor connected to ground. This had the opposite effect on the audio signal when compared to the capacitor connected to the audio jack. When 1 microFarad capacitors were used, only the very lowest frequencies were let through. When capacitance was decreased, the amount of frequencies being let through increased.

This is the last circuit I built that is only the audio signal running through to diodes between the audio jacks. The audio was heavily distorted, and I'm not sure if this was the intended result. It was basically only static and distortion, and no frequencies were actually discernible.

Questions

1. In order to half the volume of an audio signal, the resistance would have to create a voltage drop equal to half of the source voltage before the current reaches the audio jack. Since V=IR, V/2 = I(R/2), the total resistance of the circuit would have to be (IV/2). (Not sure if this is the answer you were looking for).

2. As explained above, the capacitors would affect the range of frequencies being passed into the audio jack. The higher the capacitance, the higher the frequency cutoff would be. The inverse was true when the capacitor was bypassed to ground. The higher the capacitance, the greater the range of frequencies  let through.

3. The diodes heavily distorted the signal. Once again, not sure if they were used correctly. I placed them essentially in the formation that the resistors were placed in the first circuit. Look at the last photo to see exactly where they were placed.

Final Project Questions

1. If I were to produce something similar to the ResoDrum,
http://www.instructables.com/id/ResoDrum/
I would definitely try to add some knobs or sliders that allow you to adjust the quality of the sounds without using software. This would also mean that I would need to make some sort of oscillator or sound source to completely get rid of the need for a laptop. Perhaps some sort of reverb control would be cool too.

2. As I just mentioned, I would probably get rid of the need for a laptop by using an oscillator for the sound source. Also, I'm not sure exactly how difficult electromagnetic transducers are to produce, so I might need to find an alternative for that.

Lab Report 1

Experiment Recap

In class we were taught the basic layout of a breadboard, as well as the process of attaching a voltage source to start running current through different loads on the breadboard. The first circuit we assembled was a circuit that lights an LED that consisted of a voltage source, a resistor, and an LED. The positive terminal of the battery was connected to the red strip on the edge of the breadboard, and the negative terminal was connected to the blue "ground" strip. The resistor was connected from a point on the red strip to a point in the same row, and the LED was connected from another point in the same row to the ground strip, effectively completing the circuit. We also made a similar circuit that inserted a potentiometer in between the red strip and the resistor, which allowed us to adjust the resistance of the circuit, and therefore the amount of voltage reaching the LED. This class was my first introduction to working with physical circuits, and though I had some trouble keeping track of all of my parts, I found it not too difficult and fairly satisfying once I got it to work. Of course, these circuits were extremely simple, so I look forward to more complex and challenging circuits in the future.

Questions

What are the conductive paths on the bread board?
The red strip and the ground strips run up and down each edge and all points on these strips are connected to all other points on the same strip. All points on each row are connected as well, but the rows aren't connected with eachother.

What are some easy mistakes to make with breadboards?

From my limited experience, it seems that it can be difficult to remember the flow of current within the breadboard. I tried to connect the potentiometer all along the same row instead of across three different rows, and I also know you have to keep in mind the direction of an LED, as it only accepts electricity if it's input through a specific side.

How can you make a button or switch out of two wires connected to the breadboard?

You can make a button or switch by having one wire attached from the red strip to a row, and the other wire attached from a point in the same row to the ground. When you disconnect any end of either strip, it breaks the circuit, effectively acting as a button or switch. 

Why was the resistor connected before the LED?

LED's can only handle a certain amount of voltage before they are damaged. The resistor causes a voltage drop in the current before it reaches the LED to ensure a dangerous amount of voltage doesn't pass through it.

Final Project Progress

Favorites

Malakai
http://www.youtube.com/watch?v=0VqRxa1ohw4

Tom
http://www.youtube.com/watch?v=KpL-BDLvRVo

Jake C
http://www.youtube.com/watch?v=hc4eHqzw9Dg&list=UUwDh2OuqUb-n6f1cAxyC_wA

Other Ideas

Vintage Drum Machine Replica
http://www.youtube.com/watch?v=1871fozlMSk

ResoDrums
http://www.instructables.com/id/ResoDrum/

Electronic Sitar
http://nicksworldofsynthesizers.com/stringresonator.php