So, for my Build 18 project this year, my partner Alex and I wanted to do something cool and awesome. I had a few ideas floating around, and I had seen Nirav Patel’s post on the subject of virtual reality gaming with the PNI SpacePoint Fusion. Alex thought it was a good idea, and so we ran with it. As it turns out, PNI has a nice student sponsorship program if you get in touch with the right people, and they were willing to send me their USB version of the SpacePoint Fusion (a discontinued product?!) as long as I did a writeup about it! For those of you that are interested feel free to check out my notes on the wiki (Linux, math, and coding is involved), otherwise check out my video below! I’ll hopefully be demoing it during ECE Day in a few weeks, so feel free to check it out then too.

Click here to view the embedded video.

Ruby: http://d.pr/7uHv

Sketchup File: http://d.pr/H69R

In other news, in updating WordPress to version 3, parts of my old theme broke. Thankfully new themes are really easy to install in WP, so we’re back up again! New stuff should be coming (DIY DJ!) over Christmas break, so stay tuned…

P.S. A fun related math video!

ECE majors: STOP! This one’s for you! Think about the problem, and see if you come up with the same conclusion that I did below!  :)

So, what was the fix? Basically, the clippers were designed to charge the battery which in turn would power the motor drive for the clippers. When the batteries start dying (in this case, under a year or two), you are unable to use the clippers unless you get a new battery or pay shipping and handling to Conair for their 5-year-warranty (on a $20-$30 clipper set). The fix is to simply desolder the battery from the circuit board, causing it to work just like a wired clipper should! Now, I’m not sure if they did this on purpose, but it clearly is a poor way to go about getting repeat customers for your products. I hope they fix this in future versions of the product, and if not always buy a wired clipper!

NOTE: On the newer clipper, it has some sort of auto-adjust “SMART” feature for automatically some more power to the motor. This caused the clippers to turn on temporarily and then turn off again right away when I tried turning it on. I believe this is from some sort of current limiter on the chip inside, and the only way I could fix it was by flicking the power switch up and down a few times and trying to hold my fingers on the blades to stop it from moving, sort of conditioning it with a higher load than it normally runs at. Once you get it working, it should work normally if you keep it running.

Attached are some glamour shots of the circuit board (I de-soldered the B+ and B- wires and heat-shrinked it for good measure) and of the really cool motor assembly that generates the back and forth motion (a rod offset from the axis of the motor). Hope this helps, and leave any questions you have in the comments!

I spent some time over the last few months continuing my electronics tinkering, and I’ve successfully completed two new gadgets along with a friend from school, Billy Keyes, as part of a week-long extravaganza at CMU called Build 18. It’s for ECE majors exclusively, and turned out to be a lot fun!

WARNING: Technical information follows. Skip down to the end for the pictures

Hard Drive Speed Game

When I got home from break, I was really anxious to try out a project that I ran across that made a “Spin The Hard Drive” game out of old 1-5 GB hard drives that weren’t being used anymore. So, getting the permission of my Dad, I ripped apart his old Western Digital and started playing with it. Since I didn’t have a scope back home, I had to guess a little bit on the values of the resistors for my voltage comparator. After a while, the green LED on my Arduino shield started blinking when I moved the hard drive, so I knew I hit the right spot. After adding a little hysteresis with a feedback resistor, it was working consistently enough to check it with an Arduino interrupt.

Switching over to the Arduino, it was pretty easy to set up an interrupt routine and convert over to RPM. See below for the code I used:

/*Hard Drive RPM Monitor*/
 
int interruptPin = 2;
long oldtime, difference = 0;
volatile int clicks = 0;
volatile long oldclick = 0;
int rps, rpm;
 
void setup() {
  Serial.begin(9600);
  Serial.println("Serial works...");
  pinMode(interruptPin, INPUT);
  attachInterrupt(0,click,RISING);
}
 
void loop() {
  if (clicks >= 4) { //Every 4 "clicks" is one rotation
    difference = micros() - oldtime;
    oldtime = micros();
    clicks = 0;
 
    //Rotations per minute
    Serial.println((int)(60000000.0/difference));
  }
}
 
void click() {
  //One "click" is 1/4 of a rotation
  //Delay should get rid of most false signals
  if (micros() - oldclick > 100) {
    clicks++;
    oldclick = micros();
  }
}

After making a little GUI in Processing to receive the Serial data from the Arduino and display it on the screen, I was ready to go! In the picture below, I show someone getting a high score, and the fastest I’ve seen people spin it is around 1350 RPM, which is pretty ridiculous! At Build_18, someone suggested using the hard drive as a DJ mixer, which sounded really cool and will probably be where I will go with this hard drive next!

Keepon Tracking

Our second project involved an old security camera with a built-in internet connection that I got for free last year. When I got around to buying the power cable for it, I plugged it in only to discover that the camera was broken (hence why I got it for free). So, Billy and I came up with the idea for using it as a dancing robot ala Keepon. After hooking up the camera, a USB webcam for facial recognition, and a microphone, we realized two things very quickly. First,the security camera only took commands every .6 seconds or else it would time out (bad for complex motion, but still ok). Second, sound data (particularly claps) are not very good for interrupts, as our interrupt would trigger multiple times during the sound wave and our various attempts to solve the problem weren’t working. To fix our sound problem, we ended up just checking thresholds on the analog values from the microphone and put in a small time delay to ignore the rest of the wave. Once we found the beats, we just moved the robot left and right in sync with the beat and in half- or quarter-time as necessary.

Overall, it was a great way to come back from break and hack around with some electronics. I’m looking forward to the next one!

After the summer, the whirlwind of school started again, and I’ve been non-stop busy with staying on top of my classes, Kiltie Band, Merritt visiting over Mid-Semester Break, and the college ministry that I’m attending (Agape). For anyone debating whether they will have time in college to attend a Christian student ministry, I would unabashedly say that the main reason that I get through weeks of studying and working is because of my relationship with my real Father, and his wondrous choice of me as someone to bless! Getting continually refreshed every few days in a solid ministry like Agape has helped tremendously, and I will cherish it long after I graduate from school. Anyways, as finals roll around and start next week I’ll keep trusting in Him for strength, as it’s worked pretty well so far. For everyone else wish me luck, and I look forward to meeting  you again!

//I had a little break over Thanksgiving, so I created a Lissajous Machine with some parts that I scrounged together. Enjoy!

I loved Reader’s Digest, don’t get me wrong. It’s one of those great bathroom reads, when you need some inspirational stories to get you through the day. However, once my parents’ membership ran out, they (Reader’s Digest) decided to take action to convince my parents that they need more money! I’m going to try a Better Business Bureau claim just for fun to see how far I can take this. Nowhere on the bill does it say that we don’t actually owe money, which makes this marketing scheme even weirder… I’ll keep you posted!

UPDATE: Well, it turns out that my parent’s didn’t check the box to decline RD’s opt-out service. Methinks they need to adjust their “billing” to at least remind someone that they’ve opted-in and can cancel at any time! Props to DayAnne at RD for the quick response and clarification.

EDIT: They mention this in a soft, soothing voice the video, but I want to point out that WES only runs during the morning and evening rush hours (5:20–10:00 and 3:30–8:00) on weekdays, which puts a kibosh in the plans of most evening and weekend shoppers. Hopefully they’ll expand this service in the future, but for now just leave an hour early from work and you’ll be fine.

Hello again! So, another update from Pittsburgh…I got the opportunity last weekend to attend Carnegie Mellon’s annual Spring Carnival and had a blast! Here’s an overview:

CMU Carnival is about 3 things–No School, Booth, and Buggy–all 3 pretty equally important. We get Thursday and Friday off of school and the festivities don’t end until Sunday afternoon, which is awesome especially when the weather is really nice! Booth is a very eccentric CMU tradition where different student groups race to finish building a mini-house around the given theme for a year. Booths ranged from a giant “Wall-E-Pi” to a Giant Peach, a nuclear fall-out shelter, and even a giant Poke-Booth. The Kiltie Band also performed our Spring Concert to start off the festival.

Buggy is the other main event that occurs at Carnival. You might not know what it is at first glance, but it’s basically a hill race with customized racing buggies (over a few thousand a pop, if you want a good one) that often hit 40 mph at the bottom of Flagstaff Hill. 5′ tall women are aggressively pursued at the beginning of the school year to drive the buggies and ensure their team’s victory. Believe me–these teams are HARD CORE. The Student Development Council beat Pi-KA’s record this year, but I put a video from last year anyway to give you the excitement of what happens. 

Only 2 1/2 more weeks of school!