App note: LEDs – The future of horticultural lighting


LEDs used in a controlled environment greenhouse farms, an app note from Würth Elektronik. Link here (PDF)

Greenhouse farms may not be a new technology but with an every growing world population and the move towards sustainability, intensive yet highly efficient and standardized food production will increasingly become the norm in future years opening a potentially huge new agricultural sector that incorporates the latest technologies from the bioscience and engineering fields. But how can researchers and personnel from these separate fields understand the mutually dependent requirements of indoor greenhouses? Photosynthesis is the process that converts water and carbon dioxide into complex carbohydrates (i.e. sugars) and oxygen using energy from light. However, although the energy radiated by the sun that reaches the earth’s surface consists of the entire spectrum of visible light (and more), plants only utilize specific frequencies of light for photosynthesis. These frequencies are related to the absorption characteristics of different pigments that are present within organelles called chloroplasts that are responsible for different functions of photosynthesis.

Light emitting diodes are solid-state, light generating components that, have become and will continue to be one of the greatest drivers in the expansion of internal greenhouses due to their advantages over incandescent bulbs, fluorescent bulbs, high-pressure sodium lamps and mercury lamps. Their main advantage stems from their ability to generate specific wavelengths of light. To meet the requirements for Horticultural LED’s for Indoor-farming, Würth Elektronik offers the WL-SMDC SMD Mono-color Ceramic LED Waterclear series of LEDs. The WL-SMDC range has been expanded to include wavelengths of 450 nm (Deep Blue), 660 nm (Hyper Red) and 730 nm (Far Red), which have been selected to match the absorption spectra of photosynthetic pigments. In addition to the existing products in the range, a diverse range of combinations is possible that can be catered to the target cultivar.

Teardown of a 65W Cree LED bulb


Kerry Wong did a teardown of a 65W Cree LED bulb:

Upon removing the glass bulb enclosure, I was a bit surprised to see that only two power LEDs were used in this Cree bulb. Typically, you would see many more lower wattage LEDs put together to achieve higher wattage ratings. The two power LEDs are wired in series. Each power LED likely consists of eight to ten LED dies inside as the forward voltage drop of these two LEDs is measured at around 70V in operation, with each dropping around 35V. There is also a reverse polarity protection diode integrated into each of these power LEDs.

See the full post on his blog.

Check out the video after the break.

3D POV display


Gelstronic shared detailed instructions of how to build this 3D POV display, project instructables here:

In my project i use a spinning helix of LED strips. There are a total of 144 LEDs that can displays 17280 voxels with 16 colors. The voxels are arranged circularly in 12 levels. The LEDs are controlled by only one microcontroller. Because i have used the APA102 LEDs i need no additional drivers or transistors. So the electronic part is easier to build. Another advantage is the wireless electrical supply. You need no brushes and there is no friction loss.

Check out the video after the break.

DIY polarity Led tweezers


Jesus Echavarria shared detailed instructions of how to make a simple tweezers for checking led polarity:

I usually assemble by hand all the boards I make. I use SMD components, especially in 0805 format for resistors, capacitors and leds. With the last ones, I always have the same problem: I need to check the polarity of it, to ensure that I assemble on the right way. To do it, I need the multimeter, select the diode position and test the led’s for the right polarity. Because on the assembly process I don’t usually the multimeter, why don’t make a tweezers to test the led’s? It’s an easy and very cheap project, and you’ll have a usefull tool when assembly boards. Here’s the result, after a couple of hours working on it ;).

More details at Jesus Echavarria’s blog.

App note: HT45F3420 LED flashlight application


Holtek’s HT45F3420 MCU provide LED flashlight application all in with minimal external components. Link here (PDF)

In traditional LED flashlight application circuits, the battery is used to directly drive the LED which will cause uneven brightness levels and the possibility of damaged LEDs due to changing battery conditions. Using the HT45F3420 for LED flash application, both buck and constant current techniques are used.

ESP32 (11) Led candle

After having published my previous article, I received some comments asking what was the purpose of a random number generator, like the one included in the esp32 chip.

Random numbers are widely used in cryptography and a good random number generator is very important to assure an high level of security, as well-explained in Cloudflare’s blog post. This is the reason why Expressif decided to include a RNG as an hardware peripheral within the esp32 chip.

Today I’m going to show you a more frivolous use of random numbers: I’ll use them to turn a led on/off, simulating a flame burning with random movement.

I’ve already explained in a different article the functions the framework includes to perform basic I/O, so the source of this example (as usual available on Github) should be easily understandable.

The led can be connected to any I/O pin: via menuconfig you can specify the pin you chose. To limit the current, I connected a 100ohm resistor in series with the led:


The random numbers the chip generates go from 0 to 4294967296 (the register is indeed 32bit wide). I therefore needed to scale the numbers to obtain an on/off interval between 50 and 500ms (4294967296 / 9544371 is about 450):

uint32_t getRandomDelay() {
  uint32_t random = esp_random();
  return 50 + random / 9544371;
Random numbers have an uniform distribution, this means that each number in the interval 0 – 2^32 has the same probability to be generated. The function above is not the best mathematical way to scale an uniform distribution, but for my purpose – light a led – I think it’s ok ;)

Here’s the final effect:


ESP8266 LED lighting: QuinLED v2.6 PCB


Quindor designed and built an ESP8266 LED lighting QuinLED project with Dirty Board PCBs:

It’s been a long time in the making but I’ve finally put the final touches on my newest revision of QuinLED! This makes it version 2.6 rev 1.00. Let’s check it out!

This post is part of a series – The index for this series can be found here.

Full details at Intermittent Technology homepage. Boards DirtyPCB order link here.

Check out the video after the break.

LED traffic light


Domen Ipavec shared his DIY LED traffic light in the project log forum:

Traffic lights are all around us, and they seem simple enough but are they really? Real traffic lights can be a very complicated system because it requires sophisticated control and coordination for smooth and safe traffic.
The traffic light I made is much simpler. My sister works in a kindergarten where kids needed a simple traffic light for when they are riding their bikes on the playground.
The traffic light uses some cheap LEDs from China, a step-up converter and an Atmel attiny841 microcontroller to change the light from red to green at a programmed interval.

More info at Domen Ipavec’s blog.

Via the forum.

Check out the video after the break.

Smoothly Modernized Nixie Display

The renaissance of Nixie tube popularity amid the nostalgia surrounding older tech has made them almost prohibitively expensive for individual projects. Seeing an opportunity to modernize the beloved devices, [Connor Nishijima] has unleashed this new, LED edge-lit display that he has dubbed Lixie.

We featured his prototype a few years ago. That design used dots to make up each character but this upgrade smooths that out with sleek lines and a look one would almost expect from a professional device — or at the very least something you’d see in a cyberpunk near-future. The color-changing Neopixel LEDs — moderated by a cleverly designed filter — allow for customization to your heart’s content, and the laser-cut acrylic panes allow for larger displays to be produced with relative ease.

The image above (and the video below) show two revisions of the most recent Lixie prototypes. There is a huge improvement on the right, as the digits are now outlines instead of single strokes and engraved instead of cut completely through the acrylic. The difference if phenomenal, and in our opinion move the “back to the drawing board” effect to “ready for primetime”. [Connor] and his team are working on just that, with a Tindie preorder in place for the first production-ready digits to roll off their line.

Considering that Nixie Tubes were originally considered too expensive for mass-produced items like clocks, it’s ironic they’re seeing a revival in hobbyist projects for just that purpose. Lixie, then, may fit the purpose for those seeing a cheaper solution without sacrificing on the quality of the result. The design is fully open-source, so get to hacking!

For a suitably cyberpunk application of a Nixie tube, check out this motorcycle speedometer. Oh, and lest you think we’re duplicating ourselves, there was another edge-lit Nixie-alike project featured here just a few weeks ago. Seems good ideas come in waves.

Filed under: Arduino Hacks, led hacks

High-Power LED + 3D Printer = Mega Flashlight

If you remember old computer magazines (or browse them today), you’ll see that back in the late 1970s and early 1980s, you weren’t always sure what you were going to do with a computer. Games were a staple, but they weren’t very exciting. Visionaries talked about storing recipes, writing Christmas letters (to send via snail mail), and keeping home inventories. You probably don’t do any of those things with your computer today, unless you count e-mailing instead of sending Christmas cards. We think sometimes 3D printers fall into that category today. Sure, you want one. But what are you really going to do with it? Print keychains?

That’s why we always like seeing practical designs for 3D printed items. Like this 100W flashlight. The electronics part of the build is simple enough: a 100W LED module, an off-the-shelf driver board, plus an old PC cooler and some batteries. But the 3D printed parts makes it all come together and it looks great!

To put things in perspective, an old-fashioned flashlight (two D cells and an ordinary bulb) puts out about 15 or 20 lumens. A halogen focusing flashlight might put out over 200 lumens. An LED array like the one used here can put out 7,500 lumens!

This isn’t the first time we’ve seen this sort of flashlight. We’ve even seen them with water cooling. That last post, by the way, talks about the difference between more expensive LED modules and the cheaper ones, which might be useful if you are planning on using these for any kind of photography.

Filed under: 3d Printer hacks, led hacks