MightyOhm » video

Flying with the Geiger Counter Kit

Jeff — Fri, 28 Oct 2011 14:34:58 +0000

Shortly after my Geiger counter workshop at the Chaos Communications Camp in Germany, @tatzelbrumm sent me this video of his kit chirping madly on his flight home to the United States.

If you squint at the laptop in the video, you can see that his geiger counter is reading over 400 CPM!

Exposure to cosmic radiation is a well-known side effect of commercial airline flights, and is even documented in the xkcd radiation dose chart (click for a large version):

Christoph sent me his data logs, which clearly show the effect of altitude on radiation exposure:

The red trace is the background level on the ground in SFO and hovers around 20 CPM. The blue trace is the measured radiation over Greenland on his transatlantic flight. The peak readings are 25 times the background radiation at sea-level!

Caution: Unless you like being hassled by the TSA, I don’t recommend flying with the Geiger kit in your carry-on luggage, much less actually using it on the plane! On his DIY Geiger Counter site, Brohogan posted some good advice about traveling with a Geiger counter.

Look! Geiger Counter Kits! And shiny new cases!

Have you done something cool with your Geiger Counter kit? If so, post about it in the forums!

How To Make A Cheap WiFi Radio

Jeff — Tue, 07 Sep 2010 15:27:05 +0000

@tinkernut just posted a video tutorial showing how to make a wifi radio for about $50 based on my Wifi Radio project.

Video: Staver Electromechanical Vane Display

Jeff — Thu, 02 Sep 2010 20:02:09 +0000

Here’s another neat video from Brian Stuckey of ineedcaffeine.com.

If anyone knows where to find more of these displays, I would love to get my hands on some!

Staver Electromechanical Vane / Flip 7 Segment Display from Brian Stuckey on Vimeo.

Macro video of a hard drive in use

Jeff — Fri, 27 Aug 2010 21:13:07 +0000

2.5 Inch Hard Drive Macro HD Video from Brian Stuckey on Vimeo.

An exposed hard drive in operation. See more here:
Hard Drive In Use Video

Sadly, there is no sound, but the video is amazing. Check out Brian’s other videos on Vimeo or at his website ineedcaffeine.com.

Kit Building Party Photos & Video

Jeff — Mon, 02 Nov 2009 19:07:43 +0000

This weekend I hosted a post-Halloween kit building party at MightyOhm HQ.

Nine close friends built Conway’s Game of Life kits from Adafruit Industries. This is my favorite kit for these kinds of workshops because it’s easy for beginners to complete in about 2 hours, and when everyone is done, you can wire all of the kits together to create one large cellular automata display. The last time I helped people build this kit was at a Make:SF workshop at the TechShop in Menlo Park.

Here’s a timelapse video of the afternoon, shot with a Logitech QuickCam Vision Pro webcam on an Eee PC 4G running Booru Webcam 2.0.

The capture interval was 5 seconds. I used Quicktime Pro to stitch the images together at 15fps and iMovie to add titles and music (Turbo Outrun by FRP from remix.kwed.org.)

I wore my Halloween costume for most of the afternoon. What am I? Most people on the streets of San Francisco had no idea…

Safety first!

Stuart was the first to finish his kit:

Soldering the kits together to form the matrix:

Nine happy kit-builders with the 3×3 matrix they created with their finished kits:

And lastly, a video of the 3×3 matrix in action:

Three people had little to no soldering experience at the beginning of the afternoon. Everyone who came went home with a working kit. Success!

Video of my NOTACON talk now online

Jeff — Thu, 21 May 2009 15:42:40 +0000

This week I finally got a working copy of the video of my talk from NOTACON 6 about hacking the Asus WL-520gU wireless router. You can either watch the embedded video above or follow the link below to Vimeo. If you don’t like either option, you can also download the m4v source file from here (thanks Vimeo!).

Special thanks to Media Archives for recording my talk!

NOTACON 6 – Hacking the Asus WL-520gU Wireless Router from MightyOhm on Vimeo.

DIY 8-bit Computer: Big Mess o’ Wires

Jeff — Mon, 02 Mar 2009 15:32:56 +0000

Steve Chamberlin created an 8-bit computer from discrete logic and called his project the Big Mess o’ Wires.

The BMOW runs at 2MHz and has 512K RAM and 16K ROM. It is constructed with primarily 7400 series logic and over 1048 wirewrap connections.

The feature list is very impressive:

It can multitask.
It has VGA video output.
It can make sounds and music.
It even runs Microsoft Basic!

Here’s a video of a music test from his site:

I am completely blown away by this project. Has someone invited Steve to the Maker Faire?? I want to see this thing in person!

Check out his site and prepare to spend at least an hour looking at all of his plans and construction photos.

Totally amazing.

Composite Video with Arduino (Daily Duino)

Jeff — Sun, 30 Nov 2008 08:51:18 +0000

Having had some experience generating RGB video signals with the PIC, I have a deep appreciation for the work these guys did in not only generating composite video with an Arduino, but also making a Pong game. The daily duino (need to bookmark that one) has a simpler example based on the same code.

PIC RGB Video – Technical Details

Jeff — Mon, 15 Sep 2008 20:41:27 +0000

This page summarizes the technical details behind my PIC LCD video project. This is a basic tutorial on how to generate analog RGB video using a PIC16F628 microcontroller.

Previous posts on this project:

Materials needed:

An LCD screen like the Sharp 4L-U4EB that accepts a noninterlaced NTSC analog RGB video signal (red/green/blue and composite sync all as separate signals). Poor quality datasheet here.
(1) PIC16F628 (the PIC16F628A should be a drop-in replacement. Sorry, I have old PICs lying around.)
A PIC programmer – I am using a K128, but support for it has been discontinued. Microchip’s PICkit2 is probably your best bet, but I haven’t used one (yet).
MPLAB - the free Microchip IDE, or a compatible PIC assembler
(1) 20MHz crystal (HC-18 or whatever fits your breadboard)
(2) 22pF ceramic capacitors
(3) 470 Ohm 1/8W resistors
(5) 10K 1/8W resistors
A 1K potentiometer for brightness control (if needed, my LCD needs one to display anything)
A regulated 5V supply for the PIC, and my LCD needed an 8V supply of its own
Anything else specific to your LCD – hopefully not much.

Firmware:

Source code (for use with MPLAB) – lcd_video7.asm
Hex file – lcd_video7.hex
Listing file (MPLAB output) – lcd_video7.lst

Schematic:

(click to enlarge)

Theory of Operation:

The LCD I chose for this project needs four main electrical signals to display video. Three of them carry color information – red, green, and blue. These three signals can vary from 0V (black) to 0.7V (full brightness). To achieve this, I placed 470 ohm resistors in series with each, as shown in the schematic. The LCD terminates each color signal with a 75 ohm resistor, so the 470 ohm series resistors serve to convert the 5V output of the PIC to a 0.7V max signal for the LCD (using a resistive divider).

The other signal the LCD needs is CSYNC – an inverse TTL composite sync signal. This signal provides both the horizontal and vertical sync for the LCD. Without these sync signals the image rolls across the display because the LCD doesn’t know where the image starts or ends. Composite sync seems to be a little bit unusual – most RGB video signals have separate horizontal and vertical sync signals on separate wires.

A horizontal line of NTSC video is roughly 64μs long. (μs = microseconds) At the beginning of each line, CSYNC is held low for 4us, then set high again. The RGB lines are held low during sync and stay low for 8μs after sync, then set to the desired levels display the desired image on that line. 2μs before the end of the line, RGB are set low again to signal the end of the visible image. At 64μs, the program loops back to start another line.

You can generate video like this but there would be no vertical hold – the image would be stable in the horizontal direction because we are generating a horizontal sync but not in the vertical direction.

To create a stable image with vertical sync, you have to create a valid “field” of video. We’re creating non-interlaced video, so every field is the same (in contrast with ordinary interlaced video used in television.) A field is composed of 262 horizontal lines. The first line is blank, with CSYNC set low for the entire line. This is the vertical sync. The next 17 lines are called the “blanking interval” and occur above the visible image, during these lines horizontal sync is applied but no RGB signals. The next line is the first visible line and consists of both a horizontal sync and RGB signals as discussed earlier. 243 lines later, we write one blank line, then loop back and repeat the process all over again. Now we have a valid non-interlaced analog RGB video signal.

The blank lines are mostly due to compatibility with old television sets that needed time to reset the electron gun for the next field. The nice thing is that they give us time to do housekeeping before displaying the next field. For example, during the blanking interval I load the image to display into memory so it can be easily read back later.

The critical thing with regards to timing is that the PIC needs to execute the same number of instructions each time it loops, such that the sync signals always occur at the right time. This is why there are a lot of ‘nop’ instructions in my code – to pad the program execution in the right spots and maintain sync. I started by counting instructions to figure out where to put the ‘nop’s, but by the end of writing the program I was using MPLAB’s builtin “Stopwatch” feature instead.

That’s it for now! If you have any questions, make use of these routines in your own projects, or just find this interesting, please leave a comment!

PIC Microcontroller RGB Video – Animations!

Jeff — Wed, 10 Sep 2008 18:06:10 +0000

Update: For those who are interested in seeing how this is done, I have posted schematics and source along with some technical details about this project. Click here to learn more.

After two days of straight coding, this is the result – two more aliens and an animation routine that toggles between 2 images for each alien and changes aliens every n frames. The alien selection routine is implemented as a state machine and uses way too many instructions, but fit within a blank line of video so I called it good. The hardest part again was maintaining a constant number of clock cycles regardless of the program flow through the display loop. This is required to maintain the video timing and keep the LCD happy.

I also changed the image lookup table routine so that the image to be displayed is loaded during the blanking interval above the top of the visible screen. This makes the pixel display much more efficient during the field but at the cost of a bunch of memory. Now instead of execution time during the horizontal line limiting the max resolution, it’s memory instead… sometimes you can’t win. If I encoded color more efficiently the memory limitation would go away.

I need to clean up the code and add some more comments, but I’ll post the source in case anyone else is interested in learning how to generate RGB video with a PIC or wants to try a similar project.

Update: The LCD display I am using is a Sharp 4L-U4EB I bought surplus years ago. I haven’t been able to find any more of them since, does anyone have a source?

Here are some still images showing the animation sequence for each alien. Click on each for a bigger version.

Red!

Green!

Blue!

Previous posts related to this project:

http://mightyohm.com/blog/2008/09/space-invaders/

http://mightyohm.com/blog/2008/09/generating-analog-rgb-video-with-a-pic-microcontroller/

Also check out my flickr set, PIC Microcontroller RGB Video.

Space Invaders!

Jeff — Sun, 07 Sep 2008 02:51:07 +0000

More progress using a PIC microcontroller to generate video. What next? Color is easy. Animations perhaps?

PS: If you start looking, these guys are everywhere.

Generating Analog RGB Video with a PIC Microcontroller

Jeff — Fri, 05 Sep 2008 07:55:26 +0000

Here is a PIC16F628 microcontroller clocked at 20MHz generating an analog RGB video signal with composite sync.

This project was inspired by Rickard Gunee’s PIC Video Howto which gave me a big headstart in writing the code. Thanks Rickard! I have been wanting to work on this project since reading the tutorial several years ago, and finally got a chance to start it last week.

There are few fundamental differences in my approach compared to Rickard’s and others I have seen in the past. His tutorial was written a few years ago before 20MHz PICs were commonly available (it uses an overclocked PIC16F84.) He also focuses on generating composite video to drive a standard television (using the AV inputs). I am generating RGB video which will interface with the Sharp LCD I had sitting on the shelf. RGB is a little different in that it uses a separate sync signal (composite horizontal and vertical sync on one inverted TTL line) and each color is brought out as a separate 0.7Vpp signal. These two differences make the RGB interface considerably easier (in my opinon) to work with, especially since the approach to composite video Rickard uses is limited to black and white.

So far the biggest challenges have been with getting the video timing right. I am writing the whole program in PIC assembly and every clock cycle counts.

More on this project soon, but until then, there are a few more photos on flickr.