App note: HT66FB574 single colour independent light streamer USB keyboard

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Another app note from Holtek this time about their HT66FB574, a USB keyboard device that can support single color LED streamer. Link here (PDF)

The video gaming industry is seeing continual increasing demand for multi-feature keyboards. These can include features such as keys with an individual LED which can display different graphical effects along with variable illumination levels. With each key having an illuminated surrounding area effect along with multiple colour and pattern changes, this allows for a more colourful and stimulating gaming keyboard.

Lattice iCE40 Ultra Plus FPGA: Gnarly Grey Upduino – Tutorial 1: The basics

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A how-to getting an LED flashing using VHDL from Harris’ Electronics:

The cheap price however comes with a few niggles, namely getting it up and running in the first place with the limited documentation. Gnarly Grey do a great job of explaining programming a starting program but don’t say much about further development. With that in mind, I’m going to run through the methodology of getting an LED flashing using VHDL. There seem to be a fair few Verilog methods but not many people seem to have touched upon VHDL with these FPGAs.

See full post here.

App note: LEDs – The future of horticultural lighting

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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

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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

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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

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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

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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:

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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: