MAKE AMENDS: from Country Scientist
In MAKE Volume 36’s Country Scientist column, “How to Use LEDs to Detect Light,” in the schematic in Figure D (page 138) the LED should be reversed, with the anode connected to ground and the cathode connected to IC1-2. Thanks to intrepid reader Rob Kuschinsky for pointing this out.
From Make Your Own D*mn Board
From Nuclear Fusor
From Desktop Foundry
Video coming soon!
From Shrink-Film Gaming Minis
From Smartphone Signal Generator
Suggestions on how to use your signal generator
Generate a signal to test a circuit. Now that you have the signal generator working, try building a simple low-pass filter using a 1k ohm resistor connected to a 0.1 uF capacitor that then connects to ground. Vary the frequency and watch how the signal output between the resistor and capacitor is filtered below 1500 Hz!
Test your speakers. Try connecting it to a speaker. Adjust the signal level and the type of signal generating (square vs sine). Adjust the frequency. Do you notice any differences? If you want to increase the output to the speaker (gain) adjust the resistor value in the op-amp protection circuit so that the gain is no longer one (unity).
Generate audio tones. Try generating different frequency tones. What is the minimum frequency you are able to generate? What is the maximum? At what point can you no longer hear the audio being generated?
Troubleshoot a malfunctioning circuit or device. Try troubleshooting a malfunctioning circuit or device. Disconnect the input of the circuit and connect the signal generator instead. Setup the generator to output the type of signal, frequency and signal level that would normally be input to the device. Now start debugging!
Experiment with a circuit. (signal into an op amp for gain and frequency response measurements) Try building a high and low pass filter using an op-amp. You can sweep through the different frequencies and record the voltage output every 1 KHz. If you plot the data how does the response look?
For an example of a circuit, visit makezine.com/go/buffercircuit.
From $5 Smartphone Projector
Flip your smartphone screen
When light passes though a lens (including the lenses in your eyes), it gets flipped, which means the picture from your projector will come out upside-down. No fear, though — we have a fix!
For the iPhone go to Settings > General > Accessibility and turn on Assistive Touch. Once activated, a little white orb will pop open that you can drag around the screen. Click on the orb and go to Device > Rotate Screen.
This will allow you to flip applications like the Photos app, which would normally rotate itself right side-up. Android users can download the app Ultimate Rotation Control.
Or if all else fails you can just stand on your head.
Taking It Further
- Other stand ideas include this ultra-portable Tiltpod, this handy dandy Gorillapod, or this super creative lego stand from this cool tutorial.
- Use a large aperture camera lens with a focus ring for more flexibility with projection size and focus distance.
- Use your magnifying glass to get an up-close perspective on your phones pixels.
- Try using your computer screen instead of your phone as the display in a new projector project.
- Check out this crazy sophisticated DIY digital projector that can create a 120″ HD screen!
- This mini film projector fits in the palm of your hand and was made from an Altoids tin!
- Leave it to the Japanese to do something this awesome with a projector. Hint: Samurai swords, shadow battles.
Check out Instructables user MattBothell’s smartphone projector project, which inspired this project.
From Vinyl Silk-screen Printing
A More In-Depth Tutorial for Creating the Graphic
Choose a picture The image you choose should already have reasonably high contrast. In these two examples, I picked some photos from my Flickr account. One was a Neil Young concert, and the other is a penguin I met on a beach in South Africa.
If your image is overly cluttered, or doesn’t have high contrast, you will need to do extra editing work. This editing is possible, but may be frustrating if you are doing this for the first time. I use GIMP for image editing: http://www.gimp.org Download it for free and install it. The program is pretty powerful, though it may take a bit to find the tools.
Crop the photo so that it just has the features you want. To crop the image, put a selection box around the parts of the picture you want. Then go to the Image menu, and choose ‘Crop to Selection’ The parts of the image outside the box will be discarded.
Adjust the contrast The best way to do this step is with the Threshold Tool. This tool will convert a color image to black and white, and give you sliders to control the dark (contrast) and light (brightness) in one dialog box.
The way I used to do this was with the brightness and contrast tool, but it usually took a bunch of times to get it right, and often it didn’t work at all. If you don’t get the image just right, you will need to go around with the eraser tool and remove a lot of excess detail. Threshold is the way to go. Remove all the little bits you can with the Threshold tool, then clean up the image as needed with the eraser or paint brush. You want as much of the image as possible to be made of decent size shapes. If there are too many ‘crumbs’ then you will have extra work in the weeding process.
A simpler image is best to work with initially. After you get some experience with the process, you can work with more complex compositions.
How to Make a Silkscreen Screen
If you don’t have a screen already, stretch one. You can use a pre stretched screen, which is the simpler option. Otherwise, follow the steps below.
You can buy a painter’s picture frame made of wood for this step. You’ll need a piece of silkscreen mesh that is wider and longer than the frame. Make sure the surface where you’re going to put the screen is flat, smooth, and free of staples.
Staple one edge of the screen to one side of the frame. Start in the center, then pull the screen straight as you staple the end of that same side. Pull the screen straight again as you staple the other end of that same side. Staple the centers of each section until your staples are about 1 inch apart. Use a hammer to flatten the staples.
Pull the screen to the opposite side of the first side stapled. Staple the center, then the ends of this side, pulling as you staple. Staple the centers of each section until your staples are about 1 inch apart. Repeat this process for the other two ends of the frame.
When your screen is stretched, it should be tight like the surface of a drum. If it is loose, then you should make sure that you are pulling on the screen until the staple is out of the staple gun and into the frame.
After the screen is stretched, trim off the excess screen material with a utility knife or scissors.
From Lite-Brite LED Clock
See the full build here.
From Toy Inventor’s Notebook