# Building an Automated Laser Turret Targeting System

Last year, [Alvaro] built a laser turret robot for the DEFCONBOTs competition. It worked pretty well, but this year, he decided to step it up a notch. Now instead of moving the entire robot laser array, he’s using galvanometers to move only the laser — he’s essentially built a mini laser projector.

A galvanometer is basically a very sensitive ammeter that moves — it can also be used as a very precise electro-mechanical actuator, for say, moving a tiny mirror. As you can imagine, you can actually build home-made galvanometers — but it’s really not that easy. Instead, [Alvaro] opted to order a few laser show controllers on eBay, and hack his way to a solution — we approve.

Wiring up the galvanometers and making some circuitry for them was the easy part. The tricky part is automating the system.

# How to Weigh an Eyelash

So you’re a boxer, and you’re weighing in just 80 micrograms too much for your usual weight class. How many eyelashes do you need to pluck out to get back in the ring? Or maybe you’re following the newest diet fad, “microcooking”, and a recipe calls for 750 micrograms of sugar, and you need to know how many grains that is. You need a microgram scale.

OK, we can’t really come up with a good reason to weigh an eyelash, except to say that you did. Anyway, not one but two separate YouTube videos show you how to build a microgram balance out of the mechanism in a panel meter. You know, the kind with the swinging pointer that they used to use before digital?

Panel meters are essentially an electromagnet on a spring in the field of a permanent magnet (a galvanometer). When no current flows through the electromagnet, the spring pulls the needle far left. As you push current through the electromagnet, it is attracted to the fixed permanent magnet, fighting the spring, and tugs the pointer over to the right. More current equals more pull.

# Vector Laser Projector is a Lesson in Design Processes

After two years of EE coursework, [Joshua Bateman] and [Adam Catley] were looking for a fun summer project. Instead of limping along with the resources they could put together themselves, they managed to get their school — Bristol University — to foot the bill!

Now Uni’s aren’t in the habit of just forking over funding for no reason, and we thing that’s why the two did such a great job of documenting their work. We’re used to seeing blogs devoted to one project, but this one has a vast portfolio of every piece of work that went into the build. Before any assembly started they drew out design diagrams to form the specification, laid out the circuit and the board artwork, and even worked out how the software would function in order to make sure the hardware met all their needs.

When the parts arrived the work of hand-populating the surface mount boards began. This is reflected in the fast-motion video they recorded including this clip which features a 176 pin LQFP. The driver board is a shield for a Raspberry Pi which drives the Galvanometers responsible for the X and Y movements of the mirror.

The video below shows off their success and the blog makes a great resource to point to when applying for work once a freshly minted diploma is in hand.

What do you think the next step should be? We’d advocate for a trip to crazy-town like this RGB laser projector we saw several years ago. Of course the same classic vector games we saw on Thursday would be equally awesome without alerting this hardware at all.

# [Fran] & [Bil]’s Dinosaur Den

I suppose I can take credit for introducing the super awesome [Fran Blanche] to Hackaday’s very own crotchety old man and Commodore refugee [Bil Herd]. I therefore take complete responsibility for [Fran] and [Bil]’s Dinosaur Den, the new YouTube series they’re working on.

The highlight of this week’s episode is a very vintage Rubicon mirror galvanometer. This was one of the first ways to accurately measure voltage, and works kind of like a normal panel meter on steroids. In your bone stock panel meter, a small coil moves a needle to display whatever you’re measuring. In a mirror galvanometer, a coil twists a wire that is connected to a mirror. By shining a light on this mirror and having the reflected beam bounce around several other mirrors, the angle of the mirror controlled by the coil is greatly exaggerated, making for a very, very accurate measurement. It’s so sensitive the output of a lemon battery is off the scale, all from a time earlier than the two dinosaurs showing this tech off. Neat stuff.

One last thing. Because [Bil] and [Fran] are far too proud to sink to the level of so many YouTube channels, here’s the requisite, “like comment and subscribe” pitch you won’t hear them say. Oh, [Bil] knows the audio is screwed up in places. Be sure to comment on that.

# Laser Spirograph exhibit repair and upgrade

[Bill Porter] continues finding ways to help out at the local museum. This time he’s plying his skills to fix a twenty-year-old exhibit that has been broken for some time. It’s a laser spirograph which had some parts way past their life expectancy.

He started by removing all of the electronics from the cabinet for further study in his lair. He examined the signal generator which when scoped seemed to be putting out some very nice sine waves as it should. From there he moved on to the galvos which tested way off of spec and turned out to be the offending elements.

A bit of searching around the interwebs and [Bill] figured out an upgrade plan for the older parts. But since he was at it, why not add some features at the same time? He rolled in a port so that just a bit of additional circuitry added later will allow shapes and logos to be drawn on the screen. One of his inspirations for this functionality came from another DIY laser projector project.

Take a look at the results of the repair process in the clip after the break.

# Laser light show features full XY control via homemade galvanometers

[Rich] over at NothingLabs has put together a really cool laser light show that you really must see in an effort to win a laser cutter from Instructables.

His walkthrough discusses the mechanics of laser light shows – specifically how galvanometers are typically used to precisely aim mirrors in order to draw images and write text. Commercial galvanometers tend to be pretty expensive, so he opted to build his own, using relatively cheap and easy to find parts.

The galvanometers were constructed using a pair of old speaker woofers, a few Lego bricks, and some acrylic mirror squares. The mirrors were mounted on the speakers, which were then wired to an Arduino. He removed the batteries from a cheap red laser pointer and permanently wired it to the Arduino, which it now uses as a pulsed power source. Once he had everything built, he positioned the laser using a fog machine for guidance.

As you can see in the video below, the laser show is quite impressive. His homemade galvos provide a somewhat rough quality to the final projected image, and we like that a lot. It looks almost as if all of the text and images were hand drawn, which is a pretty cool effect.

Just as [Rich] mentions, we hope to see some cool hacks based off his work in the future.

If you are interested in some of our previous laser features, check these out.

# Another home-built laser projector

[Jarrod] sent us a link to this home-built laser projector after seeing a different projector that we featured yesterday. This system is fundamentally different. [ChaN], who finished the project several years ago, didn’t use a loudspeaker to move the mirrors, but instead build his own closed-loop Galvanometers. Two of these are controlled by an ATmega64 to produce incredibly clean and accurate vector images. It’s not just the images that are impressive, his hardware is laid-out with skill and forethought that make hiding it in a case a sacrilege.