This post is a compilation of a series of Physical Computing exercises. I confess to having allowed them to build up (mea culpa, Professor).
The first image is from an exercise where we read varying resistance into one pin of the Arduino.
In the image above you can see that I have a Light Emitting Diode (LED) on my board which isn’t the wiring diagram for the project. I often use LEDs to make certain that what I am working on is powered.
The image of the board below shows the convention of wiring as I read: left to right. To the left, red is high. To the right green is ground. Rotating the test fixture a quarter turn puts the Arduino at the top, ground at the bottom. Pretty similar to printed wiring diagrams/schematics.
Going slightly off-tangent, I believe in the power of hot glue, which is actually not a glue at all. Hot glue is a relatively low-melt plastic which is used as an adhesive. I have to make a separate post about hot glue and its use/misuse in the studio.
Great tool if you use it right. It will take your skin off if you do not. As with every tool, you must pay attention to what you are doing.
In this image below you can see that I put a generous dollop on the back of an 8 ohm speaker to hold a power connector in place. Yes, this is waste of a connector. But since I am powering the Arduinio via the USB cable, I had a perfectly good connector available to use on the board. I also didn’t have any self-adhesive velcro which I use from time to time.
BTW – once in a while (more often than not, really) things don’t go quite as you think they should. I’ll leave you to cite your own examples. But this uncertainty is part of building anything.
After running the PWM code for the circuit under test, I kept getting inconsistent results. No longer able to afford pulling one single hair out of my head out of frustration, I was able to call on Professor Feddersen. Jeff came over, took a look around the board, asked a couple of questions, and somehow we looked at the connections to the speaker. Turned out that one of the connections had ALMOST broken loose and was held in place only by a tiny bit of PVC insulation. This was the cause for the intermittent and eventual total failure of the speaker’s operation.
After thanking my professor, I resoldered both connections AND – as you might have guessed – hit them with another generous helping of hot glue. Here the hot glue not only acts as an electrical insulator. It also acts what is called a “strain relief.” The stranded speaker wires are allowed to flex within their length as they are moved about – not at the solder joint which could (did) easily break free.
The image below shows a terrible use of a male-male header strip, hacked into submission to become an electrical connector. The cool thing about header strips is that the pins (these are square for wire wrapping) are plated to not only prevent oxidation, but also to be easy to solder (yay!). The pins are also on .10″ centers – just like the holes on the experimenter board.
Yes, I feel guilty about the profligate waste of space and material. Usually I am much more frugal with materials. But – there was a bin of them and they looked so… available!
This means the header can be pressed into the experimenter board with relative ease. Bad thing about the headers is that they are not designed to be used the way that I am using them. This means that they will easily snap (they are actually designed to do that!). You probably know what that means? Yes. More hot glue to the rescue. Again the molten plastic will keep the wires from flexing at the solder joints and, as a bonus, the plastic will help to prevent the strip from breaking apart.
You can see from the photo that I used several pins for each of the four connections which I needed. I could have done with a lot less wasted space. But there weren’t a lot connections in the project and I wanted to have more mass and material to work with than less – especially given how delicate the part was.
Building these homework projects was a little frustrating. I didn’t have all the correct resistor values in my NY studio. Unless you are fortunate to have walking access to unlimited proto-typing resources (you should have seen what they had available at Bell Laboratories!!) challenges will present themselves when converting an idea into a physical object whether you are in your studio or on location far from home.
When you start building you need to be able to use everything around you to get the job done (before the opening!) and not go running to Radio Shack (or crying to your mom).
Factoid #3,456: Improvisation is one of the keys to successful hardware hacking.
Resistors are about the easiest thing to work with. They are inexpensive when you buy them in bags/boxes of 100 – 1000 pieces. I use a lot of 1/4 1% metal film resistors. There are other flavors (carbon, wire-wound, non-inductive, etc) but for most of my applications, this is what works for me.
At the bottom of the image above is an example of how resistors in series will add their value – put twelve 220 ohm resistors together and you will measure 2640 ohms (2.64 k).
In parallel (like in the image below) their value goes down by 1/2 and their current dissipating ability is doubled. In other words, two 1/4 watt one thousand (1K) ohm resistors in parallel will have a new value of 500 ohms and be able to dissipate 1/2 watt of energy before bursting into flames! (Just kidding, they rarely burst into flames. But they can get hot enough to burn you if you do something wrong.)
Other experiments included generating tone(s) using the PWM command – which is a powerful tool. I might use this command to control a stud welder I recently purchased from Craigslist. For class we used this command to sound some tones. With Classmates Justin and Corey, we worked on making a light-sensitive musical instrument. The hardware was simple. The code was also simple for reading one input. We had trouble getting three to work at the same time.
Hmmmmm….. now don’t these amazing things look interesting???
(to be continued…)
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