It is time again for the annual beer can derby race! This year my gravity racer derby car is an atomic bomb :) It is da bomb, I hope it doesn't bomb har har har
I had to wait to post this project due to the very nature of its secrecy. Now that I have completed and used it for its purpose (with great success), I can post some details here.
I was thinking of a clever way to propose to my girlfriend. My thoughts dwelling on some large display, I had thought to write her name in the sky. I figured a simple way to implement this would involve a laser projection of some sort with a cloud as the screen. So my quest to build a laser show began. The thoughts actually began sometime in May. The beginning of summer was spent on research and I had used this last month of summer, August, to build, test, and use the machine.
Searching the net for how a laser show works I quickly found other people doing DIY versions of it. The one that looked most practical for me to take on in the time frame I had was this one: http://www.instructables.com/id/Arduino-Laser-Show-with-Full-XY-Control/ It involved parts which were easily obtainable from second hand stores and electronic shops.
This laser show was built using audio speakers with mirrors glued to them controlled by a micro controller. The laser will point into the series of mirrors and as the speakers goes in and out, it will swivel the mirror creating a laser display. To make it a little more portable, I housed the whole thing inside two speaker boxes (the ones that the speakers already came in). Furthermore, I made it able to be powered by a 12v battery and switched on remotely using a radio controlled switch.
I slowly purchased pieces of the machine. I acquired a green laser pointer and an Arduino microcontroller from Amazon for about $60, some speakers at Good Will for $6 a pair, various electronic parts from the R. Shack and Fry's, a power supply I got from wrk, and the rest is scraps I gathered from various sources.
I used wood from an old box spring in order to screw the two speaker boxes together. Cutting openings in the boxes allowed everything to fit inside. Once the laser was properly aligned to shoot at both mirrors, the next step came to programming the actual show. This is where I spent most of my time. A couple animations I took from the demo code which I found the instructions to this build. The rest I coded manually and painstakingly by drawing lots of graphs and trying to plot out pictures using numerical coordinates. Shapes or lines to be projected were translated from coordinates of a 255 by 255 unit square. For example a horizontal line moving all the way across would be plotted as moving the laser from point (0,0) to (255, 0).
Not going into the details of how time consuming this was, I later realized that though I had a working laser show, I had no way to present in the outdoors it if I was limited to plugging it into a wall outlet. Unfortunately, I realized this limitation two days before I was scheduled to propose. Luckily, I was able to do some quick purchases to obtain an inverter with battery, adding to my costs about $140. I plan to return these parts if I can.
Here is some video of the various build phases and the final product.
I executed the plan in August on my birthday so she was quite unsuspecting. The two nights before I spent all evening testing and staking out places to do it. After much walking around the city lugging this giant heavy laser machine, I found the perfect place. Red square on the UW campus was perfect space wise, privacy, and in ambiance. The night before the proposal I tested the machine using Kane Hall as the projector screen. I found it entertaining that by standers that watched commented that they would marry me. I was elated that the visibility, and scale turned out so good.
The day of the proposal I had taken her to Jazz Alley to witness some great and upcoming Jazz musicians along with a couple Jazz legends performing along with some fine dining. Afterwards I suggested we have a night picnic for some dessert and to watch the stars. Getting to campus, I hauled the machine out of my car in a luggage case explaining that it was "picnic supplies" (she must have been suspicious). Setting up the picnic area, I had told her to close her eyes as I had a surprise. Setting up the machine and aligning it quickly, I pulled out the remote switch and the ring which I had stashed in the luggage case. The show started when I gave her the remote and she opened her eyes.
Things went quite well in my opinion. When she first saw this machine, she thought it was a bomb and was afraid to throw the switch. However when the show had gone through and ended, I was on my knee and she was in tears (of joy I presume). She said YES and I couldn't be more happy of the results.
I was quite lucky with my timing because just as the show had finished, campus security had rolled up in a van and asked me if I was waving a laser around. I admitted yes and he cautioned me to be careful not to shoot it at the planes and I agreed and told him I had put it away. SUPER!
This video was taken after the proposal and show was presented once, so this is a recording of the second time through. It was a do-over so I could record something, kinda like how presidents do speeches twice, once live for real and a second time to get the camera shots.
For some time I wanted a cheap way to do some video surveillance. There have been a number of occasions where it would have been quite handy to have recorded video such as when the house was broken into, or when a mysterious animal continuously defecated in the yard, or when leaving for vacation and wanting to keep an eye on house visitors. I'd thought I try to create a system using the spare junk I had or could acquire at low cost.
I decided to use a VCR since they are practically junk these days and can be easily obtained from a Good Will for 5 bucks; much cheaper than hard drives DVR systems. A single VHS tape could last 6 hours in record time. To stretch this maximum record time even further I made the system only record a short period once it detected motion.
I imagined a circuit that upon detecting motion would automatically press record, wait a period (say a minute) then press pause or stop. To implement motion detection I re-purposed my Harbor Freight driveway detection system which is pretty much a PIR motion detector that transmits a radio signal to a receiver which sounds a bell during motion. The motion sensor would act as normal but an activation signal would be taken from the receiver that would manipulate the VCR.
I was given a broken digital camera which turned on but did not take pictures, luckily the CCD capture device still worked along with its video out capabilities. This easily converts into a CCTV camera by plugging in a power adapter, the video out cable, and turning off the auto-off feature. I took it apart to take out the IR filter for night vision capability.
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