F/stop printer for analog printing black and white photos

This beautifully crafted device is a timer used for getting the perfect exposure when making film prints of photos. But in addition to keeping time, it also does logarithmic calculations that are based on the f-stop values used for each exposure. It does this in 1/100th of a stop increments. While he was at it, [William] also decided to pack in a bunch of other features like dry down correction, and support for making test strips. This is a little hard to understand when discussed in the abstract, but just take a look at his video after the break where [William] walks us through an example exposure and all will become clear.

You can see from the construction page that the device is basically an Arduino shield. It provides a relay for controlling the exposure lamp, a keypad, rotary encoder, and character LCD. Slap it in a fancy case, connect it to the equipment you’re using, and you’ll be creating perfect prints in no time flat!

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Tri-rotor helicopter with full autopilot

Quadcopters stand aside, here’s a three-rotor helicopter we think you’re going to love. The body is made out of plywood and carbon fiber rods, keeping it light enough to be easily lifted by just 3 motors while making sure the force doesn’t tear the aircraft apart. Three gyroscopes, two accelerometers, three magnetometers, and a GPS module are all used in conjunction for an autopilot system. There’s a lot of great pictures and videos but our favorite, embedded after the break, shows the tricopter writing messages in the sky using light and camera exposure tricks similar to this ground-based trike.

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Single LED ultraviolet exposure box

[Jacques Lebrac] built a UV exposure box for printed circuit boards using just one LED. He usually makes boards that are just a few square inches and didn’t think building a box that had upwards of 80 LEDs was worth his time. He passed by the low power LEDs for a single 5W unit. Pumping 1.5A through this LED makes for some quick exposures, but causes heat issues. To solve this, an aluminum arm was used to mount the LED, acting as mechanical support and heat sink at the same time. The voltage regulator was glued directly to the chassis, providing at least some heat dissipation.

[Jacques] came up with an eloquent solution for holding the transparency and copper clad in place. A piece of acrylic is hinged on the back using a piece of aluminum tubing. The front has a magnet glued to it, with another one in the base to hold the cover tight to the work surface during operation.

Building a UV exposure box

There are two methods of using etchant resist when making circuit boards. We use the toner transfer method that requires ironing on laser toner to the copper, but you can also use chemical resist that reacts to ultraviolet light. [Bogdan] decided to start doing more of the latter so he built a UV exposure box to make the process easier.

It is possible to use flourescent light bulbs for this, but he decided to use UV LEDs, a method we’ve also seen before. But there’s always room to innovate, and [Bogdan] built-in a couple of nice features that are new to us. Because the UV light can be bad for your eyes, he included a set of red visible-light LEDs on the bottom half of the box that are used to align two layers of exposure mask when making double-sided boards. There’s also a switch that automatically shuts off the UV light when the box is opened. And as the coup-de-grace, he added a programmable timer to regulate the exposure, using his newly created box when etching the PCB for it.

Beer can pinhole camera

When [Justin Quinnell] sent in his beer can pinhole camera, we were just floored. The parts are easy to obtain, and the process for building and ‘shooting’ with the camera are near effortless.

The really impressive part of this hack is letting your camera sit for 6 months facing the sun. Yes, you read that correct, a 6 month exposure. Check out after the break for one of his astonishing shots, and trust us, its well worth the click. [Read more...]

Time lapse light sculptures


[Jared] sent us a feature he posted involving time-lapse photography and an LED. Using a custom built aparatus an LED is moved on two axis’ during a long exposure of around thirty seconds. The frame is wood and PVC with two gearhead motors powered by AA batteries to provide the locomotion. The LED is powered by a 3v button cell and automatically transitions through different colors.

Experiments in polaroid


[Peter] found that Polaroid film was an easy medium to play with, as the ability to develop it is built in. He has done several fun experiments, from electrocuting it to making giant mozaics. The Polaroid film may not be easy to get your hands on though. They stopped producing it in the summer of 2008. Some former employees are trying hard to get it back into production, but that may never happen. Polaroid has recently received permission to sell itself at auction. We’ll just have to wait and see.