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September 29, 2004

Lab 3 - Analog Input

Analog input. I built an audio preamp and a level meter.

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I cheated a little with this lab. I did the first few steps, and then my group project sort of took things over. The group project, however, is very similar in spirit to the lab. There's lots of analog input and variables and whatnot.

Step 1 (1mb avi)

I couldn't get my serial output to work so I used the flashing rate of an LED to measure the input from a pot.

Step 2

I got the serial output working (it was a wiring issue) and I was in business with a flex sensor.

Step 3 (.4mb avi)
another video (1.2mb avi)

Ok, here's were I start cheating. Our group project is to create a souped-up sound meter for a beer garden. The idea is that when the sound level gets too high, our system can warn the patrons, they quiet down, and beer gardens don't have to close early anymore.

In order to do this, we had to rig up a microphone up to our pic. This required us to make a pre-amp. I used a circuit from another ITP student's journal.

Here's what it looks like on the breadboard:

Then, we wired 7 LED's to create a level meter.

None of this was too hard to wire. However, the software was a bit more difficult. We found that the output from the pre-amp was erratic. Our first attempt to tame the signal was take the average of 100 samples. However, this resulted in a value that never fluctuated. Now what we do is take the maximum value of 100 samples and use that for our output. The results are consistent with noise levels.

Here's the code.

Now, what makes this different from a normal level meter that you would find on a stereo? Well, there is computational power available to us in that chip. With software, we can log noise levels over time. What we will do with this information is not clear at the moment.

Posted by rus200 at 11:17 PM

September 22, 2004

Lab2 - Digital Input

I built a combo lock and had a problem with using a 20 mHz clock.

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Here's Step 1 (1mb avi). Millions of man hours to create a pic chip, and I turned it into a light switch.

I had a problem with a 20 mHz clock, where the pic would only run if I touched the clock. In class today I learned that this could have been remedied by changing the preferences in the EPICWin program to "High Speed." Since I didn't know this at the time I switched to a 4 mHz clock.

Step 2 (1mb avi) went pretty smoothly.

For Step 3 (video below) I decided to make a combo lock. The idea is based on the directional controller of a game pad. To open the lock, you enter a code very similar to cheat codes in a video game; Left Right Up Down, for example. Conceptually it is pretty simple. It took me very little time to draft the code, but it took hours to debug and get working. I had a lot of trouble with what I think was a short in my board. Also, having to take pic chip out of the board and into the pic programmer for every compilation was very time consuming.

I rigged up a serial output to help me along. Here's a sample of the output:

Here's a video of the finished combo lock:
Third Step -- Combo Lock (6mb AVI)

If I press the buttons once each, from right to left order, the lock opens (the green light turns on). Any other order and the lock remains closed. In the movie, I touch two wires to activate a reset.

Posted by rus200 at 09:39 PM

September 16, 2004

The Story of My Name in One Paragraph

My name is Robert Underwood Seward. Each part of my name is English in origin. Robert means “famous brilliance,” Underwood means “under wood,” and Seward means "High admiral, who kept the sea against pirates, from sea, and ward, a keeper." While my last name comes from my father, my first and middle name come from my mother. Robert was the name of my mother's father, who was the District Attorney of Amarillo Texas, and Underwood is my mother's maiden name.

Posted by rus200 at 02:47 PM

September 15, 2004

Lab 1

I put together my breadboard/container setup and built a tripwire.

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I started out with only parts:

After a lot of trouble, including trying to get a broken soldering iron to work for about 20 min., I got my board and box in order.

Step 1:
What you see above is Step One. I got the LED to light up.

Step 2:
I wired three LED's in series and they did not light up. Using the multimeter, I measured the voltage from the positive prong of each LED to ground. The readings were 5.1V, 3.4V, and 1.7V. The voltage form the negative prong of the last LED in the series read 0. The LED's where lowering the voltage by about 1.7 volts each, which is a total of 5.1 (1.7x3)--that's equal to the total available voltage. There was too much resistance for the electricity to get through the LED's, and they didn't light up. I rewired them in parallel, and they all lit up.

Step 3:

I wired a 10k pot between into my circuit in series after the first 220 Ohm resistor. Turning the pot adjusted the brightness of the LED.

Step 4:

When I was a kid, I read in some project book how to make an alarm system out of a radio. It involved creating a tripwire out of clothespins and tinfoil. I took a clothespin and wrapped some tinfoil-like metal around the two halves that form the clamp. After gluing them there, I soldered a wire to the foil on each half. Now, if the clothespin is closed, the a cicuit is completed; open, it is broken.

Open:

Closed (Notice the lit-up LED in the background):

Now for the trip-wire. All that's needed is an insulator that will sit in-between the contacts in the clothespin. Attach a rope to the insulator, and when the rope is tripped, the insulator will pull out and the circuit will close. I glued two peices of plastic around some nylon line.

Voila! A tripwire!

Posted by rus200 at 04:11 PM