Sunday, August 21, 2011

Remember To Do Some Good.

It was probably Saturday morning 4:00 A.M. the week of when I was taking one last look at my inbox out of shear bored-i-ness. I remember getting the e-mail from Jean about volunteering for another robotics camp, and that I had forwarded the information to some of my colleagues and friends. No responds from either group..

4:15 AM
There wasn't anything on my agenda for the upcoming week, not in the mornings anyways. I just had to meet with a potential employer on Monday. I told myself I would go only if I could get another friend to come, but after waiting for several days with no reply, I thought about just sending a courtesy response in case they were hopeful about having extra volunteers. I wasn't going to do it.

4:25 AM
One Piece on Hulu.com. Amazing anime. It was probably on the war with Whitebeard saga that I was on.

4:45 AM
I was getting sleepy and tired. Only my fellow night owls were active on facebook. Not less than 24 hours ago, I had returned from a bicycle trip from Lake Mead. My body was still recovering from the sun and 45+ mile ride. Still in front of the desktop, I looked down at my hands to read a that message written down on my keyboard.
I guess putting it there did it's purpose. Reading something is all the motivation you need sometimes.

4:51 A.M.
The e-mail was sent, and that was it. 
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The event was a girl scout robotics camp. Apparently it was my 2nd time doing it. Or not - a year or less ago they told me, I had done the same thing. It was called something different back then and was less formal. Throughout the week I was there, I got to meet and re-meet some interesting people. Among them Ms. Gari Lindsey, the current VP of the LVV section of SWE; Josh Mauro, who I discovered was also a mechanical engineering undergrad at UNLV; and Monica LeFebvre, a lady who helped coordinate programs with the girl scout group. They're shown in the following photo.
Everyone was so serious. Notice the serious face in the foreground. Such seriousness.

Josh kept getting hassled by the younger girls. They loved us, maybe a little too much. I was quickly reminded of old times with my baby sister after seeing them jump him and fight for his attention. This was the reason why I stayed away from the younger girls. There were around 35 girl scouts working on a series of tasks. By age range, they were divided into two groups. 

Most of my time was spent offering advice on the NXT Lego Mindstorm kits assigned to the older girls. The most challenging task they were assigned to including using a 3rd motor to control an arm that picked up objects located on a mat and placed them at another location. All of them wanted to used pre-routed programs. My IEEE friends would've panicked >.<

On Friday, came judgement day. Kim Womack came by to judge one of the events, and I was assigned to aid. My performance as a judge was less than that of an educator. I believe the main goal of it would be to perform a professional evaluation on a list of required task in order to showcase to the parents what the girls have learned. She was indeed a professional.

At the end of the day, there was a pizza party and Josh and I were handed this.
I was appreciated and have the certificate to prove it.
We  received "Thanks-A-Lot" cookies by the girl scouts. By the way, if you haven't tasted them, they are delicious! If memory serves right, the chocolate fudge has a sort of minty taste to it which makes these cookies unique. The accompanying mug was unexpected as well. Aside from the material stuff, earlier in the week an 11 year old girl scout had said "Thank You" to me and smiled. The first of many thanks received. All the rest actually had diluted the value of the phrase, but that first one had made my day. It was totally worth volunteering my time throughout the week. These young ladies will grow up and build weapons of war one day. And cure cancer. They'll also cure cancer. With robots*

Wednesday, August 10, 2011

Wall-A's "Arm" and V_o

Greetings world!

For at least one person, it'll be obvious why I've posted this. Several months back I began working on a project involving an ATMEL based micro-controller, some servos, and a few sensors. The goal of the project was to experiment with different differential-drive algorithms, and to gain experience with the spiffy soldering iron I 'burrowed' from my step-dad. Originally, the project ran on a homemade augmented micro-controller, but later moved onto an Axon II because I was a noob and the thing had more documentation than the relic tomes ATMEL offered.

The baby I brought into the world was given the name of "Wall-A." She is a 2 wheel differential drive critter with an ultra-sonic sensor, and 2 homemade light sensors made out of cheap cadmium sulfide (CdS) photoresistors that are cheaply available from the Shack. I'll be giving a brief overview of the schematics involved with the photoresistor set up.

First off, this is a CdS photoresistor.
In absolute darkness, you can consider it to be in the off position. The voltage potential running through the leads would be 0. If photons from light hit the surface of this circuit element the pathway for current running through the leads is opened. Effectively, higher levels of frequencies correlate to a decrease in the resistance this pathway offers. In the photo below you can see me holding a photoresistor connected to a multimeter and pointing it towards a lamp.

In order to make a useful application of this for data logging, it's best to take advantage of something known as the voltage divider rule. The standard equation governing this circuit is set to calculate what the out voltage is.
(eq1.1) v_o = R*v_i/(R+R_p), where v_o = voltage that gets read by the micro-controller, R = resistance provided by a static resistor, v_i = voltage coming in, R_p = the variable resistance provided by the photoresistor which is correlated to the intensity of the light hitting the circuit element. It is R_p which we are trying to solve for. The schematic and soldered circuit looks like this.

The voltage across each resistor in a series circuit divides in direct proportion to the individual series resistances. Thus, you can always determine the proportion in which voltage drops are distributed around a circuit. Since we are solving for R_p, eq1.1 rearranges to
(eq1.2) R_p = ((R*v_i)/v_o) - R

Again, R_p correlates to the intensity of the photons hitting the surface of the photoresistor. In plain English, it gives you a calculated value based of an analog reading from the circuit. Ahh.. It would tell you how dark or not dark it is outside.

So this is how you would create your very own light sensor. Typically they sell for ~$5 on the market, but if you have the materials at hand, you can make your own in as little as a couple minutes. These sensors are currently being used on the Wall-A prototype to help the little guy stay hidden in the darkness. He is a photophobe you see.


Yes, that is a 2x4, duck tape, and cardboard you see. Wall-A is an incredible advanced high-tech prototype and will be doing stuff like curing cancer, or harassing neighborhood cats one day.