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901  Forum 2005-2010 (read only) / Exhibition / Re: SSTV/POV project- Step 1 on: December 23, 2010, 02:16:10 pm
Yeah, I'm hoping I can use a lens or two and spin a few mirrors and get away with that, basically doing a poor-man's raster scan.  The arduino could easily handle the timing, the phosphor retention once dry is quite long, if you wanted to, you could take the better part of a minute to draw a video frame and the phosphor would still be working for you if you hit it at close range with UV.  When I said "SSTV", I meant SLOW scan.  I know there's got to be a few HAM guys here, and probably a few have SSTV stuff on a shelf.

People I think likely have SSTV equipment on a shelf:  Cr0sh, Grumpy Mike, Westfw.. a few others.  

I may even build the world's ghetto-est Oscilloscope.  In fact, I think that's kinda a stepping stone, anyway... that's just a single scan line.  Using a couple of motors, I may just be able to drag the LED around on the glass for a totally hackjob solution.
902  Forum 2005-2010 (read only) / Exhibition / SSTV/POV project- Step 1 on: December 23, 2010, 11:01:42 am
Yes, you can buy LCD panels for a buck on Ebay.

Yes, with the TVout Lib you can use any television as an output device with only two resistors.

Yes, for very cheap money, you can have a number of very high resolution output devices which perform wonderfully, with almost no effort at all.

Arduino is about making the difficult much easier.. so, I of course will be using the Arduino to take a relatively simple and inexpensive task and make it into a very involved and cumbersome technological nightmare.

How you ask?  By seeing if we can build our own TV screen, of course.  This started as an idea for a toy for my daughter to encourage her to head to bed early and shut off the lights (a continuous problem), but for that purpose I will use Plexiglas rather than actual glass, to prevent risk of injury from broken glass.  As I'm using a picture frame, this isn't even tempered or very thick glass, and would shatter into many sharp shards.  For toy purposes, almost any surface would work, but for what I'm attempting I may have better luck being able to illuminate the panel from behind.  A kid's toy would only need to work from the front, so you could just paint it directly on any surface.  I still would consider the lexan however, because it would provide a smooth surface and protect the actual paint layer, if you were "painting" with UV through the plastic.

I found a gift card I needed to use while unpacking xmas items.. so Home Depot and Rustoleum got $8 for a 7oz can of Phosphorescent Glow In The Dark paint, and the local discount store got a dollar for an LED keychain UV light.  Throw in a cheap photo frame, and we have a proof of concept on the basic idea.  

Already, it would make a cute toy for any kid, even us 40-something year old ones...  not "Arduino-ized" yet, but begs for it.  Even without the Arduino, I'd recommend this as a great home-made gift for a kid.

Once the screen itself is done, it's then time to think about the best way to provide for scanning across the surface, bitmapping our image.  I'm hopeful about being able to use either some lenses and a mirror with a UV source (by far the best reaction from the phosphor), or ideally a laser.  UV ranges would work the best, but standard red may still provide enough radiant energy to drive the phosphors.  UV lasers aren't cheap and can be dangerous, but blue/violet lasers are becoming cheaper due to blu-ray disc players.  Blue/violet laser pointers in the 405nM range are now becoming reasonable, but at this point I don't have one to mess around with.  As I don't have a blu-ray player to chop up, we'll start with UV led's and/or pocket cheapo red laser pointer.  Ideally (for a lot of reasons, not the least of which are financial) I try to use items in my projects that people ought to be able to pick up almost anywhere, and cheaply.  So far, the most expensive and esoteric item is the can of Glow In The Dark paint, which is made by Rustoleum and can be gotten at home stores, craft stores, and probably even at Walmart.. at $8 for 7oz (about 200ml).  

903  Forum 2005-2010 (read only) / Exhibition / Re: Lunar Lander on the Arduino on: November 23, 2010, 09:06:05 am
Great stuff... I've been thinking about doing something like this myself!

MUGWUMP.. CHOMP.. HAMARABI.. I have a stash of code that hasn't seen the light of day for decades.  I'm not sure how many were ever printed, much less how many still exist (though I'm sure the code's actually still out there on the net).. but I have an original copy of DEC's original "Game Programming in PDP BASIC"- and I've been thinking about porting those great little throwacks.  Somehow, I don't think we can get a MORIA instance going on an AVR though.. well, then again... hmm...

Great job!
904  Forum 2005-2010 (read only) / Exhibition / Re: Arduino + Led Matrix + Bad Apple!! on: December 05, 2010, 01:59:55 pm
From what I see, I think he's sending the picture over in a straight bitmap.  He mentions that decoding is not done topleft to bottomright, his looping code (on the PC, done in PHP in the code he posted) takes care of that.  He's just using a serial connection, I think..  The Arduino is then displaying that bitmap on the LED grid.  24x16=384pixels.  One pixel per bit, so that's only 48 bytes for the full image, probably passed as just a stream of CHAR or BYTE values, 48 bytes long.  Serial handles that even at slow speeds.

Pretty good framerate.. now you need a way to produce the PNGs downconverted from uncompressed AVI frames... so that on one side you just feed in a video file and on the arduino, the best approximation is mapped on the LED matrix..

905  Forum 2005-2010 (read only) / Exhibition / Re: Thermography on the cheap on: October 13, 2010, 04:42:58 pm
Hmm.. interesting, to say the least!  

Among the things I have not yet hooked to the Arduino is the IR camera module from a WII remote, which is supposedly a really nice blob-tracking unit, but needs an external I2C interface and a clock.  Clocks are easy enough (need 25Mhz so software prolly won't do), and the I2C I was going to offload onto my soon-to-arrive TI Launchpad.  I figure that might just be an acceptable use for the little beast, at under five bucks, it'll have earned it's keep if it can support interfacing to that sensor... told ya I could find a better use for a Launchpad than a glue spreader!
906  Forum 2005-2010 (read only) / Exhibition / Re: Claw Machine Game on: December 10, 2010, 11:07:02 pm
Where do you get the little kid to stick inside?
907  Forum 2005-2010 (read only) / Exhibition / Re: Trash Sorter on: November 29, 2010, 09:51:08 am
You could get tricky and use a solonoid or a servo as a striker and a microphone to pick up the resultant sound.. glass will make a notably different sound than plastic I would think.  The other way would be density, but you have no way of knowing the wall thickness, which could make a thick-wall plastic bottle seem by weight to be a glass bottle instead.

Pull out a 'scope and a microphone and see if there's a usable difference in the sounds generated by a striker.  I'd think that glass is going to make that characteristic short-duration "tink", while plastic would be more deadened (tapping my coffee cup and a plastic Iced Tea bottle here) sound.  If so, a little creative coding can probably differentiate the two.  Come to think of it, metal would have it's own particular "clunk" too...

I'm just thinking about how we as humans tell whether it's glass or plastic or whatever.. and one of the first things any of us would do is to tap it, and listen to the sound it makes.  It works for us, so maybe there's a solution in there that Arduino can use too..
908  Forum 2005-2010 (read only) / Exhibition / Re: Remote controlled car lift on: November 29, 2010, 09:42:02 am
Hmm.  Now, you need to add a couple of photosensors to have it stop at each floor... though now that I think about it, you can likely do that by experimenting a little bit in terms of number (or degree) of rotation in the servo which corresponds to the elevator aligning with the floor..

That, and I'm 90% sure I had that exact Fisher Price garage as a kid, four decades back...
909  Forum 2005-2010 (read only) / Exhibition / Re: Pong Meter on: November 29, 2010, 04:46:20 pm
At any given flow rate it looks pretty stable, so I would think that varying the fan speed with PWM might be enough, without needing to use some type of feedback sensor.  It would be a build-then-calibrate rather than a build-to-meet-calibration setup, but I just can't see using a ping pong or beach ball as a high-precision indicator.  That being said, PWM ought to give a pretty fine degree of control...
910  Forum 2005-2010 (read only) / Exhibition / Re: Pong Meter on: November 29, 2010, 10:01:35 am
Heheh.. I think I'm going to give this a try, at least a very simple version.. but on a grander scale.  In the basement, I have a standard box fan (110AC), and I've got a couple of inflatable beach balls left over from the summer..  PWM to a Triac (or a pair of SCRs) for the speed control... betcha a box fan could hold a beach ball on an air column several feet high...
911  Forum 2005-2010 (read only) / Exhibition / Re: Pong Meter on: November 27, 2010, 07:35:18 pm
AWESOME idea.  I love it.

My only comments:  Remove the tube, it won't be needed.  The pingpong ball can ride an air column just fine... the column pushes the ball back to center.  Remember your middle school science teachers doing this with a vacuum cleaner?  If I remember right, it's bournoulli's (?sp) law in play, air rushing around the curved surface creates a pressure well or something like that; I'm sure you can find the "why" out there on these here interwebs, but skipping theory, it works in practice so the academics aren't strictly necessary.

That, and then color the balls with fluorescent paint and front-light it with either a standard black light or some high-power UV LED's..  I'm already visualizing a spectrum analyzer made with a series of these.... what's the "response time"?  No matter what, the fall rate won't exceed gravity, how fast does a 0%-100%-0% cycle take?
912  Forum 2005-2010 (read only) / Exhibition / Re: Arduino Realtime Spectrum Analyzer with Video Out on: November 23, 2010, 11:24:51 am
I had been looking at the stats for the blog, which includes the URL's followed to reach the site.. which then showed me two things... I made the Arduino blog the other day with this the project (grinz) and here's the one that I'm kind of proud of:

Referenced in Make magazine's blog, too!

I really ought to fix up that amp circuit, huh?  I was thinking of using an op amp instead of beefing up the simple transistor amp, but then it would lose the shine of all being run from a single chip (yes, I know, but let's just play along with the misnomer).  Guess a darlington pair might be the right solution.. the amp "design" was "hey what's laying around in the bin?" and hasn't exactly been designed for ideal operation..

After turkey day, I'll take a shot at the circuit.  Three main design changes, hopefully without much added complexity:

1) increased gain on the microphone for better sensitivity
2) adding a direct-coupled input, for taking in line-level and/or headphone-jack-level input, so it can be "fed" from an audio device or mp3 player
3) maybe some type of filter cap to reduce AC hum

A few changes in code also make sense, maybe beefing up the graphics a bit too, as they are meant to be a light show, not an analytical device... not to mention, the circuit as posted shows the capacitor reversed, etc... "Fritzing" isn't something you just load and get right the first time, methinks..
913  Forum 2005-2010 (read only) / Exhibition / Re: Arduino Realtime Spectrum Analyzer with Video Out on: November 19, 2010, 02:15:49 pm
Circuit is now posted (first Fritzing attempt.. bear with me!) and a second video is going up...

Six resistors, a capacitor, a microphone, and a transistor  (I got six resistors and a microphone....)
914  Forum 2005-2010 (read only) / Exhibition / Re: Arduino Realtime Spectrum Analyzer with Video Out on: November 15, 2010, 04:47:05 pm

It doesn't help that the music is coming from a cheap speaker held by hand over a breadboard-mounted microphone either, I'm willing to bet.  Since the amplifier gain is not really where it should be for clean samples, a bit of data noise is also the result.  The fact that it worked at all the first time through is nothing short of a miracle- I'm cleaning up the circuit a bit before I post it also, as it is a total trainwreck on the board (see the pictures in the blog).

As for FPS, I'm going to time it after I do a few tweaks.  Right now, it's actually skipping the first band, due to a large amount of 60hz hum.  I may have to put some filtration in to take some of it out, also it will help if I run from battery rather than a half-wave rectified wall wart, I'm sure.

However, happened upon some hockey game tickets for tonight's game (Boston Bruins v New Jersey Devils).. I'm not a lunatic fan, but I like going to almost any kind of live event, if only to people watch.  It's a good way to reassure yourself that you really AREN'T the biggest freak of nature on the planet.  The Bruins will be getting my attention for the next few hours.. but I'll probably be doing some twiddling with the beastie over the next day or so.

If I had to venture a guess, I'd say it's probably in the 10-12 FPS range.. the Tvout line drawing is actually the big cpu hog...  I find that amazing, as the transformation provides 64-band data, roughly 500Hz per band, to give us 0-32kHz (roughly) on the display in 64 bands, in realtime, in C, on an AVR.  Very impressive, poor little AVR has got to be going flat out!

Incidentally, the code should work if you have another source feeding the Analog input... I used a microphone for this version (plug into TV, set it down, and it displays ambient sound on TV), but a direct-coupled version of course would be much cleaner.  The resistors for the TVout library (one 330ohm, one 1kohm) are the only hardware required other than something feeding the A/D input.  Conversion to whatever source is simply a matter of getting a decent signal to the A/D converter.

I'm considering a circuit that would use PWM to charge a capacitor to feed the aref pin... thereby making aref variable by changing the PWM ratio... giving me a sort of automatic gain control via software, on the analog inputs.  Got any thoughts on the feasibility?  As you know, I'm likely to attempt things that I don't know any better than to try.. and sometimes succeed...
915  Forum 2005-2010 (read only) / Exhibition / Re: Arduino Realtime Spectrum Analyzer with Video Out on: November 14, 2010, 08:40:44 pm
Hmm.. well, converted to AVI and YouTube preferred that.  Here's video of it running, "listening" to a little AC/DC.

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