Upgrading an Old Camera with a New Light Meter

Hackaday Solar Hacks -

[Marc] has an old Voigtländer Vito CLR film camera. The camera originally came with an analog light meter built-in. The meter consisted of a type of solar panel hooked up to a coil and a needle. As more light reached the solar panel, the coil became energized more and more, which moved the needle farther and farther. It was a simple way of doing things, but it has a down side. The photo panels stop working over time. That’s why [Marc] decided to build a custom light meter using newer technology.

[Marc] had to work within the confines of the tiny space inside of the camera. He chose to use a LM3914 bar display driver IC as the primary component. This chip can sense an input voltage against a reference voltage and then display the result by illuminating a single LED from a row of ten LEDs.

[Marc] used a photo cell from an old calculator to detect the ambient light. This acts as a current source, but he needed a voltage source. He designed a transimpedence amplifier into his circuit to convert the current into a voltage. The circuit is powered with two 3V coil cell batteries, regulated to 5V. The 5V acts as his reference voltage for the display driver. With that in mind, [Marc] had to amplify this signal further.

It didn’t end there, though. [Marc] discovered that when sampling natural light, the system worked as intended. When he sampled light from incandescent light bulbs, he did not get the expected output. This turned out to be caused by the fact that incandescent lights flicker at a rate of 50/60 Hz. His sensor was picking this up and the sinusoidal output was causing problems in his circuit. He remedied this by adding two filtering capacitors.

The whole circuit fits on a tiny PCB that slides right into position where the original light meter used to be. It’s impressive how perfectly it fits considering everything that is happening in this circuit.

[Thanks Mojay]

Filed under: solar hacks

Using The Sun To Beat The Heat

Hackaday Solar Hacks -

It’s practically May, and that means the sweltering heat of summer is nearly upon us. Soon you’ll be sitting outside somewhere, perhaps by a lake, or fishing from a canoe, or atop a blanket spread out on the grass at a music festival, all the while wishing you had built yourself a solar-powered personal air conditioner.

[Nords] created his from a large insulated beverage vessel. The imbibing spout offers a pre-made path to the depths of said vessel and the heart of this build, the ice water refrigerant. [Nords] fashioned a coil out of copper tubing to use as a heat exchanger and strapped it to the fan that performed best in a noise-benefit analysis.

A small USB-powered submersible pump moves the ice water up through the copper tubing. Both the pump and the fan run off of a 5V solar panel and are connected with a USB Y cable, eliminating the need for soldering. Even if you spend the summer inside, you could still find yourself uncomfortably warm. Provided you have access to ice, you could make this really cool desktop air conditioner.

[via Embedded Lab]

Filed under: lifehacks, solar hacks

Modern Spin on an Old Technology

Hackaday Solar Hacks -

It seems that the longer a technology has been around, the more likely it is that all of the ideas and uses for that technology will be fleshed out. For something that’s been around for around 5500 years it must be especially rare to teach an old dog new tricks, but [Sebastian] has built a sundial that’s different from any we’ve ever seen.

Once done with all of the math for the sundial to compute its angles and true north based on his latitude and longitude, [Sebastian] used Autodesk Inventor to create a model. From there it was 3D printed, but the interesting part here is that the 3D printer allowed for him to leave recesses for numbers in the sundial. The numbers are arranged at such angles inside the sundial so that when it’s a particular hour, the number of the hour shines through the shadow of the sundial which creates a very unique effect. This would be pretty difficult to do with any machine tools but is easily accomplished via 3D printing.

[Sebastian] wanted a way to appreciate the beauty of time, and he’s certainly accomplished that with this new take on  the sundial! He also wonders what it would be like if there was a giant one in a park. This may also be the first actual sundial build we’ve featured. What does that mean? Check out this non-pv, sun-powered clock that isn’t a sundial.

Thanks to [Todd] for the tip!

Filed under: solar hacks
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