Measure Laser Wavelength with a CD and a Tape Measure

Obviously the wavelength of a laser can’t be measured with a scale as large as that of a carpenter’s tape measure. At least not directly and that’s where a Compact Disc comes in. [Styropyro] uses a CD as a diffraction grating which results in an optical pattern large enough to measure.

A diffraction grating splits a beam of light up into multiple beams whose position is determined by both the wavelength of the light and the properties of the grating. Since we don’t know the properties of the grating (the CD) to start, [Styropyro] uses a green laser as reference. This works for a couple of reasons; the green laser’s properties don’t change with heat and it’s wavelength is already known.

It’s all about the triangles. Well, really it’s all about the math and the math is all about the triangles. For those that don’t rock out on special characters [Styropyro] does a great job of not only explaining what each symbol stands for, but applying it (on camera in video below) to the control experiment. Measure the sides of the triangle, then use simple trigonometry to determine the slit distance of the CD. This was the one missing datum that he turns around and uses to measure and determine his unknown laser wavelength.

Continue reading “Measure Laser Wavelength with a CD and a Tape Measure”

High Speed Laser Based Camera Flash Trigger for Only $2

Laser Triggered Camera Flash

[Matt Kane] works at a really cool company in the UK where he recently finished working on the Triggertrap Ada — the highest-performance, most feature packed camera trigger out there. So just for fun, he decided to challenge himself again — could he make a super basic, super fast, bare-bones camera trigger for $2 instead?

At the most basic level this is just a laser pointer and a light sensor. When the object your photographing breaks the light path, the flash triggers. Typically this is done with an IR laser, but since he’s going for a low-cost system, he’ll use a basic 1mw red laser pointer — the only downfall is you might see it in the picture.

Next up is the sensor. Ideally we’d use a photodiode which is very fast, but also expensive. A photoresistor is cheap, but not fast enough. A nice medium between the two is a phototransistor, which is relatively fast, and cheap. Finally, we need a minimum trigger period to offset the flash. [Matt] thought about using a 555 timer but instead decided to just generate a pulse with an Attiny45.  Continue reading “High Speed Laser Based Camera Flash Trigger for Only $2″

Hackaday Links: February 23, 2014


You can pick up a tiny laser pointer on the cheap if you know where to look. But when it comes time to replace the multiple button cells that power it be prepared to clean our your wallet. [KB3WZZ] got around that with the cap from a ball-point pen. He drilled holes in the end plug of the pointer, and used wire and a plastic pen cap as a battery adapter. He’s powering it from USB, but now that you have wires exiting the case you can use any source you wish.

[Gerben] tipped us off about the trinket clone he built himself. It’s a tiny sliver of a PCB which he etched, populated with through-hole parts only, and finished off with some finger nail varnish to prevent shorting and corrosion. The solder-covered edge connector for USB was left unvarnished of course.

If you live in a college town you are probably quite used to seeing futon pads and frames on the curb waiting for the garbage collector. A little bit of ingenuity, and some added lumber, will turn a futon frame into a respectable shelving unit. [Thanks Martin]

Complicated bench equipment + good lighting + a great camera = an awesome teardown. This time around it’s the guts of a Keithly 2002 8.5 digit mulitimeter laid bare. [Thanks David]

Here’s a PCB laminator hack that is definitely worth a look. The original unit was acquired on eBay for about $25 and had a thermostat whose performance wasn’t optimal. A bit of alteration for the thickness of the substrate, and you’ll never hand iron a toner transfer board again! [Thanks William]

Last summer we heard about Scout, an ocean-going drone trying to cross the Atlantic. We just checked the live tracking and the craft is still at sea. But a much smaller 5ft vessel made it from New Jersey to Guernsey (an island between the UK and France) after traveling for about 14 months. [Thanks Rob]

Laser toting robot taunts house cat


[Rodney Lederer] and his cat were bored after moving to a new city. He fixed that for both of them by taking on this project which turns a Wowwee robot into feline entertainment.

It’s no secret that cats have a weakness for the little red dot produced by a laser pointer. [Rodney] put that trait to work by automating the movement of a red laser pointer. After mounting it on a servo motor he got down to work programming an Arduino to move it in a playful manner. But it wouldn’t have been much fun if the this was only capable of preprogrammed patterns, so he also included an IR proximity sensor to help give the thing interactivity. Add to that the treaded robot base and you’ve got mobile cat entertainment. The proof is in the video after the break… the cat is certainly having fun chasing the dot. [Rodney] plans to work a bit more on his code so that the motions of the laser dot include a lot of different patterns to keep things exciting.

Continue reading “Laser toting robot taunts house cat”

Hackaday Links: January 5, 2013

Do not aim laser at remaining eye


Over on the reddits, [CarbonGod] thought he had a slightly overpowered laser pointer. His red laser pointer had a label that said it outputs less than 5 mW. The only problem is it melted black plastic and heated a thermocouple up to 140°F. [CarbonGod] is begging, borrowing, or stealing a power meter from an engineer friend, but until then we’ve got measurements from [The_Sourgrapes]. His lasers put out 105 mW (red), 56 mW (blue), and 53 mW (green).

While <5 mW lasers are fairly safe, these lasers that are labeled as having < 5 mW of output are not. Now if we only knew where to buy these overpowered lasers…

 It’s impossible to find this video in HD


[Zach] created a physical rickroll device. It’s an Arduino and an MP3 shield hooked up to an ultrasonic sensor. When someone walks within six feet of the device, the Arduino starts playing Never Gonna Give You Up. When that person walks away, the song is paused only to start again when something else is detected by the ultrasonic sensor. There’s a hilarious video of [Zach] triggering his physical rickroll device, or you can check it out on the build page.

Hey, you! Write some code!


[William] wrote in to tell us about a project called ReactOS. The goal of the project is to create a free and open source operating system that is binary comparable with Windows XP. Yes, this project has been around for a very long time, but with Microsoft dropping support for XP, the ReactOS team could really use a few devs to get a beta out soon. If you know a bunch of low-level Windows stuff but haven’t ever contributed to an open source project, check out the developer’s wiki.

I’m [Johnny Knoxville] and this is electrostatic discharge


It looks like [Mehdi] is making a few instructional videos for EEs and those tinkering around with electricity. So far he has tutorials for making proper wiring connections, what not to do with ESD, how to take capacitors for granted, and demonstrating how electricity can kill you.

Penitent man shall pass…. Penitent man shall pass…

If gift giving were a contest, [Bradley] would win. His sister’s favorite movie is Indiana Jones and the Last Crusade, so when he needed to wrap a gift (a coffee cup, fittingly), he went all out. All the challenges required to obtain the Holy Grail are present in this present including the breath of God (needs more circular saws), the name of God (why was the letter ‘J’ even in the movie?), and the Leap of Faith (sand included).

Coming up for his sister’s birthday, a face-melting hair dryer.

Control your house by moving your arms like you’re directing traffic

This home automation project lets you flap your arms to turn things on and off. [Toon] and [Jiang] have been working on the concept as part of their Master’s thesis at University. It uses a 3D camera with some custom software to pick up your gestures. What we really like is the laser pointer which provides feedback. You can see a red dot on the wall which followers where ever he points. Each controllable device has a special area to which the dot will snap when the user is pointing close to it. By raising his other arm the selected object can be turned on or off.

Take a look at the two videos after the break to get a good overview of the concept. We’d love to see some type of laser projector used instead of just a single dot. This way you could have a pop-up menu system. Imagine getting a virtual remote control on the wall for skipping to the next audio track, adjusting the volume, or changing the TV channel.

Continue reading “Control your house by moving your arms like you’re directing traffic”

Update: Laser-powered auto focus assist version 2

We don’t know if our feature from a couple of days gave [Adrian] a kick in the pants, or if he was just on target to finish is writeup this week, but he’s posted about version 2 of his laser auto focus assist project.

The original idea was to use an unfocused laser pointer dot to give his DSLR auto focus feature a kick in the pants since the built-in light doesn’t come back on when photographing moving subjects. The original version worked, but he had to operate the laser manually and the hardware was kind of spread out all over the camera.

The latest version (2.0) can be seen above, housed in a project box that mounts to the hot shoe and keeps everything together in one package. The laser operation is now automatic, coming on when the shutter trigger is depressed half way, or when the auto focus enable button is depressed. The controls on the project box include an on/off switch as well as a potentiometer which varies the intensity of the laser.

It looks like this won’t be the last version of the hardware that we see. [Adrian] covers a few outstanding problems in his post. Most notably, the laser light is still a bit too strong. At a recent live event, another photographer took issue with the fact that his images included the red splotch from [Adrian’s] diy hardware.