Categories

## The LED Burns Bright

Disclaimer: I have destroyed light emitting diodes (LEDs) in the past. Typically on purpose, by feeding them too much voltage until they burn out in a bright flash. It’s fun to do if you’ve got a variable power supply with a dial and can slowing crank up the voltage.

That said, this is about trying to destroy an LED without trying to destroy and LED. (Or maybe, trying to not destroy an LED but still breaking the rules.)

The rules you say? Yes. As in, you need a resistor when connecting an LED to an Arduino. This is just, like, a fact. You can get away with putting a resistor-less LED on an Arduino for testing, or learning, or a quick demo, but to do it right, always add an appropriate resistor inline.

There’s a web site called LEDCalc.com that helps you determine the appropriate resistor for the LED and voltage you are using. Tell it you’ve got 5 volts, one LED with a voltage drop of 2.0 volts, and want to give it 20 milliamps and it will tell you to use a 180 ohm resistor. (There’s fancy maths to figure this out as well, but I’m an artist who does not excel in maths.)

In the photo above you’ll see a (very bright) yellow LED connected to an Arduino Nano. (This Nano specifically is manufactured by Elegoo.) I have no resistor in my circuit, I have nothing else connected, just a single LED on a single pin, with a digital write to turn it on at full power. (As it were.)

Okay, so at some point the LED will be destroyed, or the pin on the Arduino will be destroyed, or the Arduino itself will be destroyed, or some component will fail. But… when will that happen? I’m a week into this experiment, and so far, all is well. Will it take a month, a year, a decade? Is the time to failure completely unknown, and completely random. Is it pure luck that this works, and it could fail any second now? Do I need to blink it on and off to get an inrush of current to the LED to stress it more?

I found this Arduino MEGA with 27 LEDs connected to 27 different pins, which I used for testing, and it seems fine as well. Granted, I don’t have all LEDs on at the same time for any real length of time. It’s a blinkenlights thing so lots of off time and some on time.

I’m now really tempted to change the code so it just turns on all 27 LEDs at once for an extended amount of time. I’m a bit curious about this whole thing now. I understand the reasoning behind current limiting resistors, but I’m wondering how that comes into play in the real world. One of the trickiest things I’ve dealt with when designing circuits is that they should work, they work on paper (or on the screen) but in the real world something goes wrong. EMF, physics, gremlins… whatever. Something you don’t expect comes along and screws things up… But this seems like the opposite, where we plan for what should/could go wrong, but then it doesn’t.

I probably need an actual Electrical Engineer to walk me through this one…

Categories

## Manual Crankable Larson Scanner

The most recent fun project at Brown Dog Gadgets is our take on the classic Larson Scanner. EMSL has an awesome kit, and many people who have experimented with an Arduino and LEDs have made a breadboard version.

Well, Josh and I made a LEGO version using Crazy Circuits parts, and instead of a microncontroller it’s controlled by a hand crank! Yeah, it’s an Analog, Hand-Cranked, LEGO-Based, Crazy Circuits Larson Scanner.

As with all of our projects, the instructions, files, templates and all that are available for free. Check it out! You can certainly use other components besides Crazy Circuits and Maker Tape for this, but as always, getting parts from us (or a reseller) ensures we can keep producing open source educational content and curriculum. And yes, schools, teachers, maker clubs, and other use these resources, and we incorporate their feedback into new designs and projects.

There’s a bit of an explanation about the cylinder and “coding” as it were, in the instructions. While this is a simple & fun project, you can expand upon the basic concept to talk about more advanced concepts. That’s pretty much our goal with these things.

Josh had a lot of fun making the video for this one, though I’ve heard that stock music way too many times in other videos! ;)

Perfect for your Knight Industries Two Thousand or Cylon!

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## Designing a Giant LED Cube

This year my “big” project for Maker Faire Milwaukee was a Giant LED Cube. In this post I’ll talk about designing it, and in a follow up post I’ll talk about building it.

I should mention that the idea for this started maybe three years ago. I think it was during a meeting for Maker Faire at Milwaukee Makerspace and I tossed out the idea of building a giant light sculpture using light bulbs. Lance and Chris talked about it a bit and Tom started looking up parts on Alibaba. Nothing came of it that year, and I sort of forgot about it for a while. In fact, I really didn’t think about it again until after we completed the DecaLight last year. Once the two dimensional relay controlled light bulb thing was done I thought going three dimensional would be a good idea.

I modeled the cube in OpenSCAD, and then animated it just for fun. I figured out how many pieces of each PVC joint I would need, and while I originally thought a 20′ cube would be a good idea, after some initial tests (and the unavailability of 10′ PVC pipe) I ended up going with a 10′ cube so the 5′ PVC pipe I could get would work.

I picked up Jordan Bunker’s book PVC and Pipe Engineer: Put Together Cool, Easy, Maker-Friendly Stuff last year and then ended up learning about FORMUFIT which allows you to build furniture using PVC pipe. I had a plan!

Here’s the first sketch of the Giant LED Cube. By now I had decided that I would use LED light bulbs and standard household lamp sockets. The nice thing about using such common parts is that they are very cheap. I found these Black Bakelite Fixture Socket with Terminals and ordered some so I could test the fit. It was close enough that it would work, and I just needed to make a small adapter. Well, at least 27 small adapters.

I designed and 3D printed over 30 of these using clear ABS, which is remarkably close to being white, and since you wouldn’t really see them, I was fine with the close match. I cranked these out so I’d be ready when they were needed. Like many parts of this project, they are just press fit into place. The entire thing was designed to be easily assembled and disassembled for making transport and storage an simple affair.

I had the basic design of the cube figured out, so I decided to work on the controller. Since we’d have 27 LED light bulbs I decided to use an Arduino Mega, which had plenty of I/O pins, along with two 16 channel relay boards. LED light bulbs are pretty lower power (compared to incandescent bulbs, anyway) so even though they’re 110 volts AC, 27 bulbs all on at the same time probably pulled less than 6 amps.

The image above represents my first attempt at layout out the controller, which I eventually abandoned. The screw terminals ended up not being a good idea. I would be pretty busy running Maker Faire so I assumed that I could find helpers able to strip wire, put them into the screw terminals, and get it all right. After attempting this myself on a small scale I decided that it needed to be even simpler, and clear enough that almost anyone could do the setup. So I scrapped the screw terminals. Around this time I also decided that running all of the power cords inside the PVC was going to be tedious and difficult, so with the decision to just run the cords on the outside (at least for this installation) I decided to just use standard household plugs. This would allow nearly anyone to just match up some numbers and plug things in. Simple wins!

The design process for the Giant LED Cube wasn’t too difficult. Doing this like this (designing, specifying parts, building, etc.) is pretty much my day job. The wiring was definitely tedious, and required at least one unexpected hour-long troubleshooting session due to a bad connection. I had a lot of help with the wiring of the lights from Adrian, and a lot of help with initial assembly from Becky. Without their help things would have taken me a lot longer. (Thank You!)

I think I’ve spewed enough about this project for one post (which I wanted to get out last month!) so I’ll end it here and get working on Part II ASAP.

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## Big Switch Little Light

This project started like many of my projects… Someone says something, and I have a reaction to it. I might say something, or I might not say anything, but I’ll get an idea, and decide to do something. Sometimes it’s a ridiculous idea, and that doesn’t really matter. In fact, ridiculous ideas are probably more likely to be explored.

This one started when a local teacher got in touch with Milwaukee Makerspace about donating a bunch of industrial control equipment. Luckily Tom and a few other members were interested enough to go look through nine boxes and transport them back to the space so members could look through them. I should note this is a common thing. When people want to get rid of things we look for a “Champion”. Basically someone who will take responsibility for the stuff. If they bring it to the space we ask that whatever members don’t take “goes away” within a week or so. (Typically this means the dumpster, but not always. At a minimum, some members take some things and divert them from the landfill. Sometimes things are donated to others or recycled.)

This load was a bunch of industrial electronics. Not super useful for most of our members, but many did find some good things. I found some neat switches, and in particular this large switch with a nick “CLUNK!” sound that said it was capable of handling 690 volts…

Steve and I were looking at it as I clicked it on and off and I mentioned how many volts it could handle and he said “Hey, you need to make it turn on an LED!” which was (probably) a joke, since an LED requires roughly 3 volts, which is quite a bit less than 690 volts. (In fact, it’s approximately 687 volts less!)

So I did what I had to do… I had to assemble the switch into a device that could turn on (and off) and LED. I had also found (and destroyed) an old data tape, but I managed to save the nice Aluminum plate that served as the base of the data tape. (Seriously, some of those old tapes were sort of beautiful!) Since I now had to weird objects, I just combined them with some wire, an LED, and LED panel mount, a battery holder, and two AA batteries. The rest is… history!?

There’s also a Sintra plate on the bottom that the battery holder screws into to hold it in place. And some tape, and some hot glue. (It’s not a project until you add the hot glue!)

So yeah, it’s a but ridiculous, but it’s also somewhat interesting. In some of my projects I don’t even add a switch. This actually seems very common in “maker” projects. Why add a switch when you can just apply and cut power by plugging a thing in!? So why not make the switch the BIG THING in the project. Many times larger than the batteries and the thing you’re actually turning on. Hell, it’s almost art!

Because the switch sounds so amazing, I had to make a video. Oh, also you can see the LED turn on, so there’s no trickery in this video.

Also, worse case, if I keep this thing around I’ll have a nice big high voltage rated switch I can cannibalize for another project. So that’s a big win in my book.

(Oh, sorry about the terrible photos of the blue LED. I need to do better next time.)

Categories

The inspiration came from something Kathy and I saw at Maker Faire Detroit. After seeing the “M” at the Henry Ford I remembered I had left over batteries, LEDs, and binder clips from the Learn to Solder kits I made for the Zoom Symposium at UWM.

I thought that since I had the leftover parts because of a UWM connection, I should find a way to get UWM involved again, so I persuaded my Physical Computing class to help. (And by “persuaded”, I mean I bribed my students into helping me with assembly of the piece.)

I didn’t have a piece of posterboard large enough to make the star I wanted, so I make five segments that could be assembled into a star.

Since I don’t have a printer capable of tabloid printing, I split the pieces into halves and printed on letter paper. Some assembly was required.

I cut the pieces and taped them together, and then had the “star legs” I needed. I then used it to cut the black posterboard using an X-ACTO knife and cork-backed steel edge ruler on a cutting mat. (Sorry, no laser!)

And yes… things didn’t fit right. Again, no laser. I trimmed edges a bit until things fit together right and it was deemed “good enough”.

I took the star pieces to Kenilworth and attached them to the piece of sheet metal with some magnets. At this point, I had to wait until the Thursday night right before Maker Faire, which luckily enough, is when I have class! I brought in some bags of candy, and while I taught students in groups of two or three how to solder, the rest of them assembled everything…

200+ pieces of black construction paper were cut for insulation, 200+ batteries were opened and had 200+ LEDs stuck onto them, 200+ binder clips had the clippy parts removed, and 200+ magnets were attached and then placed on the sheet metal. Things go fast with so many people helping!

Here’s the first test with the lights out, which we did during the DECODE meeting. It was impressive!

I then had to get Star-Blinken from the fifth floor of Kenilworth to my car, which was fun, because the Milwaukee Film event was setting up and Kenilworth was a bit crowded. The stand is heavy to prevent tipping, so I needed a cart. Also, since there’s no on/off switch, it blinks all the time. No control!

I loaded Star-Blinken into my car and yeah, it just kept on blinking! It was a fun ride home. It kept blinking strong all night long in the garage and then I unloaded it the next morning at Maker Faire. I ended up placing in at the entrance of the Dark Room, mainly because there weren’t other things there, but I think being in a darker area may have been even better. (I was a bit busy producing the event to worry about a better placement.)

Dana helped disassemble Star-Blinken at the Expo Center, and I asked her to just drop all the pieces into a box. After I loaded everything out and took it home, I forgot which box it was in and opening the box gave me a pleasant surprise. I then spent over an hour putting all the binder clips back together, and taking apart all the pieces.

The cost of this piece was approximately \$100, and about \$36 of that was for the batteries, which are the only parts that cannot be reused. (Well, actually, some of them have life left in them! Some did die though. None are at full power anymore.)

So I can reuse all the parts, except for the batteries, either in a similar piece in the future, or in the Learn to Solder kit. I may return the sheet metal to Tom from Milwaukee Makerspace, and the wood was disposed of. (The wood cost \$0.00 as it was all scrap, and I reclaimed all the screws.)

This is just one post in a series, check out the other posts as well: