I Am The Midnight Message Board What Messages At Midnight

January 11, 2014 by Kristina Panos 15 Comments

Photoluminescent stars on your bedroom wall or ceiling are pretty cool, though the stationary shapes can become boring. [Adi] felt this way, too. While doodling with a bright white light on some glow in the dark vinyl, it occurred to him that this could make for an interesting display. He set about making GLO, the midnight message board and RSS display.

[Adi]’s light writer uses 12 UV LEDs on a linear axis powered by a stepper motor to write RSS headlines, Twitter trends, or custom text on his wall. He finds the slow fade of the text very soothing to fall asleep by, and it’s easy to see why. The LED array imprints a section of a character consisting of a 6×5 bit pattern. The 12 LEDs are split into two groups, so it can write two lines at 45-50 characters each. [Adi] designed his own pixel font for this project, and advises that only upper case letter forms be used.

[Adi]’s write-up is quite admirable and comprehensive. In the circuit build section, he advises that the LEDs must be very close to the vinyl for optimum results, but that they should protrude farther than the shift registers so the chips don’t rub the vinyl. Of course you could opt for more intense light sources, like laser. See it in action after the break.

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Do Not Look Into 12 Watt UV Lamp With Remaining Eye

November 7, 2012 by Brian Benchoff 33 Comments

We’ve seen a couple of UV lamp builds for exposing photosensitive PCBs and erasing EPROMs, but [John] over at pcboard.ca decided if it’s worth doing, it’s worth overdoing. They designed a UV exposure board using twelve 1 Watt UV LEDs, an impressive amount ultraviolet light that you probably shouldn’t look at for too long.

We’ve seen UV exposure boxes before, usually made with a bunch of 5mm UV LEDs soldered to a piece of protoboard. These projects do their job, but the exposure time is on the order of minutes. The PCboard.ca UV lamp can expose a PCB in just 20 seconds.

The build began with four pieces of aluminum bar, 1 inch wide and 1/8″ thick. The 12 star LEDs were glued down to this bar with thermal adhesive and serve their purpose as a rather large heat sink.

[John] performed a little test to determine how long it would take this monstrous UV source to expose a PCB. By copying a PCB mask four times and placing it over an unexposed board, [John] made a PCB with exposure times of 60, 45, 30, and 15 seconds. After developing and etching, all but the 15-second exposure was fully etched, an amazing result that will probably lead to some very, very rapid prototyping.

All the more impressive is the fact that only four 1-watt LED drivers were used for this build. That’s right, this UV lamp is actually operating at about a quarter of its maximum rating, or about 285mA per LED. We’d hate to see this thing operate at full power, protective eyewear or not.

UV LEDs Expose PCBs, Gives You A Tan

September 24, 2012 by Brian Benchoff 30 Comments

Among the projects that define electronic design, a UV exposure box is right up at the top of the list. These boxes shine UV light on a work piece and are used for everything from exposing photosensitive PCBs to erasing EPROMs. [carlolog] decided to build his own and ended up with a fairly impressive array of ultraviolet LEDs perfect for making PCBs or tanning the back of your hand.

One important thing to remember when making large arrays of LEDs is current consumption and power needed to light the device up. [carlolog] naive assessment of how much power would be required used a 12 volt supply with 135 LEDs and 135 resistors, wasting a lot of energy and producing 24 Watts of heat.

Of course this power consumption can be reduced by putting a few LEDs in series, so [carlolog] wired 3 LEDs together with a 150Ω resistor. This array requires just over 11 Watts and consumes less than 1 Amp; perfect for a desktop UV box.

The enclosure for the box was crafted out of three Ikea photo frames, and a small timer circuit powered by an ATmega8 was added. Now whenever [carlolog] needs to wipe an EPROM, he can put the chip in the box, set the timer, and walk away.

A very nice build, but when dealing with a lot of UV we must remind our readers: do not look into the UV array with your remaining eye.