[Ben Krasnow] is working on a project that uses an extremely expensive specialty mirror. He needed to cut curves into it, taking care not to chip or shatter the material. He’s found a reliable way of doing this with a CNC mill and is sharing his methods.
The material he’s working with is a cold mirror; it reflects visible light while allowing infrared light to pass through. He had to custom order it, breakage is not acceptable. [Ben] explains that the biggest risk when milling glass is the clamping method used. He built his own jig and uses shims, rather than clamps, to secure the material along the X and Y axes. It is held down on the Z axis using a bar of acrylic spanning from one side to the other with rubber feet on the bottom.
A diamond burr cutter does the work, spinning at 3000 RPM. [Ben] recommends moving the head at the slowest rate possible in order to give the cutter time to do its work. And of course the material needs to be kept cool by pumping cutting fluid across it. As he shows in the video after the break, what you get is a piece of glass that comes out with clean and smooth edges.
In case we’ve sparked your curiosity, this mirror will be used during an MRI scan. The patient looks at a monitor reflected in the mirror at a 45 degree angle. At the same time, an infrared camera records the patient from the other side of the mirror to monitor where they are looking.
Continue reading “Milling curves into mirrors and glass”
The image you see above is the result of a simple analog projection clock. It shows the time on the ceiling. We have one in our bedroom but it’s a red digital display which we don’t think is nearly as fun as this clever hack. Grab a cheap analog clock, a mirror, and a white LED and you can build your own.
The mirror is going to reflect light from the LED onto a ceiling or other surface. It acts as the clock face. The tick marks for each hour were made by scratching the reflective material (often called the silvering) from the back of the mirror. A hole is drilled at the center of the class and the analog clock is mounted with its hands on the business side. The one problem with this setup is that since the light is being reflected, the clock will appear to run backwards. Not a problem, if you just reverse the polarity of the coil which moves the clockwork the projection will move in the expected clockwise direction.
[Gordon] sent us a tip about this simple laser trip wire system after reading yesterday’s post on a more complicated laser security unit. That build did a lot to provide functionality, such as a system to disarm the trip wire, and a robust light detection circuit. This time around there’s more happening with smoke and mirrors than with electronics.
[The Timmy] built this simpler version based on a laser trip system from Afrotechmods (video of that one is embedded after the break). He had a bag full of small square mirrors which he attached to a wall with some poster putty. A laser module shines a beam of light onto a cadmium sulfide sensor after it bounces around the optical network for a while. That CdS sensor controls an N-channel MOSFET, switching it off when light is detected and on when the intensity of the laser is absent. This example just turns an LED on and off, but since it uses logic-level voltages you can choose to add a microcontroller to the mix if you have other plans in mind.
Continue reading “Laser trip wire – the bare essentials”
By and large, the standard household mirror is one item that has not made much real progress over the years. They hang on the wall reflecting light, and that’s about it.
A few years back, some students studying in the Department of Interaction Design at Chalmers University sought to enhance their morning routine with an interactive mirror. Their project was constructed using a two-way mirror with several Arduino-driven LED displays embedded behind the glass. Once a hand is swiped past the pair of embedded light dependent resistors, the display is activated. Subsequent hand swipes trigger the mirror to toggle between the different modes, providing the user with the current time, weather information as well as a toothbrush timer.
The project writeup is quite thorough, including plenty of source code and information on some of the components they used. You can take a look at their work here (PDF).
Check out the interactive mirror we featured that served as inspiration for their project.
Continue reading “Bathroom mirror HUD displays time and weather”
[chromationsystems] put out a couple instructibles on building infinity mirrors. One with an 8×8 array of LEDs and one with a 32 LED ring. These are very well documented covering the construction of the mirror enclosure as well as the circuit and code. The effect is quite nice. The 8×8 array is interesting, we haven’t seen that before. These would make a fine addition to any geek cave/electronics lab. While it looks like these were basically advertisements for a product he sells, you can definitely make your own from his instructions. We like this kind of advertising.
Wielding the power to melt glass or instantly ignite most day to day materials can be
intoxicating pretty fun. With a little math, a lot of patience, and 5,800 1cm pieces of mirror, this build requires welding glasses just to look at the 1-2cm focal point. With an idea rumored to date back to Archimedes, this more portable parabolic project is perfect for your home burning needs. Unfortunately, this setup seems to have burnt itself to death at some point, though that makes room for version two, which will reportedly bump the mirror count to 32,000 or so.
There are plenty of other ways to make a death ray out there as well, including using lasers or lenses. Think you have a better tool of destruction? Be sure to tell us about it.
This laser message scroller is built with inexpensive parts. The heart of [Raul’s] system is a spinning pill-box with eight mirrors on it. Each redirects the laser to a different vertical portion of the projection surface. There are eight small arms on the apparatus that each break the beam of an optical sensors as it spins, facilitating the precise synchronization needed to generate the projected image correctly. In the video after the break we can make out what looks like an Arduino controlling the system. This makes sense as it’s easy to connect the laser pointer and sensor, and the USB connection allows for the streaming of messages to the system.
Want to see a more complicated setup? Check out the POV laser projector from a few years back. Continue reading “Laser marquee projector”