Showing posts with label LED Grow Lights. Show all posts
Showing posts with label LED Grow Lights. Show all posts

Top Ten LEDs and LED Grow Lights

Recently the LED Grow Lights market has seen a greater interest in using White HB (High Brightness) LEDS to round out and fill in gaps of spectrum that are missing within the heavily weighted red/blue fixtures that are currently available. Here is a blurb on the LED industries latest favorite white LEDs and how they are being used.

Those looking for the best LEDs to use in their lighting devices have been given a helping hand through a list compiled by one expert.

Richard Wilson, editor of ElectronicsWeekly, included brands such as Bridgelux, Cree, Enfis, Philips and Osram in his top ten.

Mr Wilson favoured the Cree LRP-38 LED for its high colour-rendering index of 92, which puts it on a par with incandescent alternatives, and the Osram Parathom Classic, reportedly the first suitable for replacing a 40W bulb.

Philips Lumileds Altilon LED bulb was also recommended for those needing automotive headlights – it is currently used by Audi for high and low beams in its R8 model and reaches more than 850 lumens.

Other mentions went to the Seoul Semiconductor Z1 LED, the Marl 742 series and the Tyco TYC06-09.

Volkswagen exhibited its new L1 concept car at the Frankfurt International Motor Show this week, which is equipped with Osrams Joule JFL2 LEDs for its front headlights.

Rapid Electronics is a leading UK supplier of LED products and optoelectronic components for industrial, educational and consumer applications.


Now fire up those trusty soldering irons and build another LED Grow Light prototype for the gipper!

Designing LED Grow Lights with a microcontroller

A recent article from Embedded.com may help walk DIY LED Grow Light builders through a simple application and design process when using a Microcontroller as a Switch-Mode Power Supply (SMPS). Though not quite as easy as some other LED Grow Light build ups on the internet, this design can be useful for both boost operation or buck-boost operation depending on the LED Grow Light application and LED voltages required.

Light-emitting diodes (LEDs) have emerged in recent years as viable sources of light and are no longer used solely as status-light indicators for electronic equipment. Advances in technology have provided LEDs that are typically three times more efficient than incandescent bulbs. LEDs are also extremely durable and have lifetimes exceeding tens of thousands of hours. Power LEDs for lighting applications are designed to be driven with a constant current source. It is common to see standard current drive levels of 350mA and 700mA among different LED manufacturers.

The forward voltage across the LED can, however, vary depending on the type and number of junctions connected in series. Many manufacturers of power LEDs will provide multiple junctions, integrated into a single module.

One simple method that can be used to drive an LED is to install a resistor, in series, to limit the current. A linear voltage regulator or operational-amplifier (op-amp) circuit can also be connected in a constant-current configuration. However, these linear methods will not have enough efficiency at the required power levels.

A Switch-Mode Power Supply (SMPS) provides a much more efficient solution for driving the LED. An SMPS can buck or boost the input voltage to the correct level, to provide the desired LED current. The system input-voltage range and the required LED forward voltage will determine the SMPS topology that is selected. Buck-boost converter
The buck-boost converter topology is used when the supply voltage may be above or below the required output voltage and is especially useful for battery applications. This topology is also known as a fly-back or inverting regulator. A buck-boost converter can be implemented as shown in Figure 1 above.

This implementation has the advantage that a simple, low-side MOSFET driver circuit can be used. The topology shown in Figure 1 will generate a positive voltage, referenced to the input-voltage rail. The downside of this buck- boost implementation is that the load is not referenced to the circuit ground.

A simplified circuit design for an LED driver is shown in Figure 2 below, using a mixed signal, high voltage 8bit microcontroller, such as Microchip Technology's PIC16HV785. The output of the circuit is referenced to the battery voltage, not to ground. The output of the inverter is connected to the LED anode and produces a voltage that is greater than the input voltage.
The PIC16HV785 mixed signal microcontroller combines an 8bit microcontroller core with several on-chip analogue peripherals. These include a high speed, two-phase PWM circuit, ideal for current-mode control of switch-mode power supplies, and two on-chip op-amps that can be used to amplify the voltage across the current-sensing resistors.

This allows the use of very small sensing resistors, which reduces circuit losses and increases overall efficiency. The on-chip high voltage shunt regulator eliminates the need for an external 5V regulator when operating from higher supply voltages.

The PIC16HV785 also integrates a digital Capture, Compare and PWM (CCP) module, two analogue comparators, a 10bit A/D converter, an 8MHz internal clock circuit, internal precision voltage reference, and a programmable Brown-Out Reset (BOR) circuit. All of the pins of the op amps and comparators are externally accessible, so that any circuit configuration can be implemented.

The current-sensing op amp is connected as a differential amplifier, to obtain an accurate measurement of the voltage across the current- sense resistor. The current is measured in the return of the power source, to simplify the requirements of the circuit. R1, R2 and C1 form a low-pass filter to reduce any switching noise that may be present. The cut-off frequency of this filter must be chosen above the converter switching frequency, to avoid limiting the control loop response.

Analogue Style Module
The two-phase PWM module, an internal comparator and a voltage reference form the circuit that regulates the amount of LED current. The two-phase PWM is an analogue-style module that works on the set/reset principle.

First, a clock signal, derived from the system clock, is used to periodically turn on the PWM output. The PWM clock signal sets the fundamental PWM frequency. Then, a reset signal from one of the on-chip comparators turns off the PWM output, when a specified reference level has been reached.

The amplified current signal is internally routed to the positive input of Comparator 1 on the PIC16HV785. The Capture-Compare Peripheral (CCP1) on the PIC16HV785 is used in the PWM mode to generate the voltage reference for the comparator. Using the PWM allows fine control of the comparator reference voltage. The PWM signal is filtered with an RC filter to produce an analogue voltage and is connected to the negative comparator input pin.

The software for this application is very simple, since the LED current-control function is accomplished in the analogue domain. After all peripherals have been enabled and a current-reference level has been set, the LED will continue to illuminate without software intervention.

However, the application code can use the on-chip 10bit A/D converter to measure the supply voltage, which then drives the LED in a constant-power mode. As the battery input voltage changes, a new voltage-reference value is produced by the D/A circuit (implemented with the CCP peripheral) to provide the required compensation.

Setting LED brightness
Since the microcontroller core is only spending a small portion of time in the power-regulation process, more time can be dedicated to the user interface and to provide additional features, such as battery status monitoring and bright- ness level control. There are two ways that the LED light level can be adjusted using this circuit and software.

The first technique relies on the principle that the brightness of the LED will change with the drive current. In fact, an approximate linear control of the LED brightness can be accomplished using this method. However, variable current dimming is not the most efficient way to set the LED brightness level. The LED achieves its best efficiency at the maximum drive-current level specified by the manufacturer.

A low-frequency PWM signal of between 60Hz and 1kHz can be used to modulate the LED drive current. Instead of reducing the current drive level, the LED is always driven at maximum current during the on-time. The duty cycle of the PWM signal sets the average amount of time that the LED is energised.

The chosen PWM frequency should be sufficiently high so that the LED current is turned on and off at a rate that will not cause the human eye to detect flickering. The PWM frequency must also be low enough so that the current-regulation circuit has enough time to stabilise during the PWM on-time. If these conditions are met, the human eye will average the light output from the LED over time.

The PIC16HV785 contains all the required components to implement an efficient high power LED drive circuit. It can be easily configured for boost operation or buck-boost operation, depending on the input voltage range.

The application uses only a small portion of the microcontroller's RAM and Flash memory, leaving plenty of room for additional application code. With enough unused peripherals on the PIC16HV785 microcontroller, a second LED driver, battery charger, or other switch-mode circuit can also be implemented.


If one of the hobbyist readers chooses to build a LED Grow Light using a microcontroller please share your project with the rest of the LED grow light readers here, using your link or comment below.

LED Lighting Replacement For Conventional HPS/HID Lights

LED Street Light
Though far from an LED Grow Light and not fine tuned for the wavelengths required by plants, this could be a direct solid state lighting replacement for Indoor Gardeners that currently use HID or HPS bulbs.

After four years of extensive Research & Development, Remco Solid State Lighting Inc., a Toronto, Canada-based SSL Solutions Company, has broken through the barrier to replace conventional street lighting with its recently patented SSL technology and LED-based street light.

Its disruptive SSL technology utilizes the dynamic resistance of LEDs providing a LED light engine that is up to 98% power efficient – only a 2% power loss that enables optimal power and LED lighting efficiencies. IES certified photometric lab results and successful pilot field-testing conducted at Camp Borden military base have verified these industry-leading levels of performance.

A number of companies have ventured into the LED street lighting market with varying degrees of success. Now, Remco Solid State Lighting has delved into this market utilizing its recently patented power efficient light engine and prototyped an LED Street Light for a truly equivalent LED replacement of the conventional cobra head street light.

“Real LED-based lighting application replacements for existing light sources must be direct lighting replacement solutions - lumen for lumen and LUX for LUX, plus offer the benefits of energy savings and reduced maintenance cost," stated Ron Russell, Remco’s CTO and inventor of Remco’s patented LED light engine. Not only is it scaleable to all lighting applications but it also offers a significant competitive advantage in high power LED lighting applications.

Conventional street lights typically use a high-pressure sodium bulb. Even non-technical people can see the difference in the picture. The CTO also conveyed that, despite having retrofitted a cobra head street light fixture with Remco’s proprietary thermal management and LED light engine using a stock HPS cobra head lens, Remco’s LED Street Light was able to outperform and produce more light at a greater efficiency than the conventional high-pressure sodium street light.

Mark Matthews, Remco's President and CEO stated, “What we strive to achieve with our SSL technology and LED lighting applications is equivalent useable lumens utilizing LEDs to replace conventional lighting with significant energy savings. Our Light engine is up to 98% power efficient and this technology is the key, especially in high power lighting applications."

According to Alex Savu, Energy Manager at Camp Borden military base in Canada (where the LED street light pilot test was performed), conventional HPS street lights consume 138 watts (100 watt HPS bulb plus the ballast which consumes an additional 38 watts) and the Remco prototype (a light engine and LED fixture within a cobra head fixture) consumed only 111 watts to generate 4770 useable lumens – a direct lighting replacement.

Matthews explained that, “While the test confirms only a 20% energy savings at 40.1 lumens per watt, these results are excellent considering that we have incorporated our LED fixture within a cobra head fixture and lost 20% of the lumens output absorbed by the standard HPS cobra head lens; whereas, we could have generated approximately 5300 useable lumens without the HPS lens.”

“When we complete our commercial product to replace all models of 100 watt HPS street lights (Note: the ballast also consumes 38 watts) with our patented LED light engine, proprietary thermal management and optics, utilizing 100 lumens/watt white LEDs, the commercial Remco LED street light luminaire will achieve approximately a 50% energy savings at 72 watts.”

It is estimated that there are 50 million 100 watt conventional street lights in North America, and we would like to replace all conventional street lights worldwide with Remco’s energy efficient LED Street Light as a contribution to help reduce Global Warming.

Alex Savu reported that since performing the tests, he has seen the superior performance of Remco's LED Street Light. He said, "The light is phenomenal. Basically, it is superior. It looks good!" He explained, "We would have to change our current units ten times before changing one of their units. The way we operate our lights, their units will last 27.4 years." (10 hours per day, seven days per week.)

Savu added, "Once we put theirs up, there were no complaints whatsoever." “However,” he said, "most of the other street lights we tested received complaints; either they were not bright enough or there was something wrong with the light."

In addition to its power efficient light engine for street lights, the company has developed a fully integrated pendant linear SSL luminaire prototype to replace fluorescent lighting capable of 66% energy savings as well fabricating prototypes of Edison-based LED bulbs with brightness levels equivalent to the incandescent bulbs they replace at energy savings of 85% to 95%!

Remco’s new LED light engine technology and SSL luminaires are gaining attention. In 2008 the company was selected as one of Canada’s Top Ten Cleantech technology companies by the Ottawa Centre for Research and Innovation.

Remco is on the verge of setting new standards in the Solid State Lighting industry and is currently seeking capital and licensing to major global lighting/fixture organizations and/or international distributors to collectively take a commanding lead in high power LED lighting applications.

Photo cutline: Remco’s Bright LED Street Light is in the foreground and conventional HPS street lights in the background.

100W LED Grow Light with 3640 Lumens


Solid State LED Grow Lights are gaining traction again, this time with a press release from Dialight (Lumidrives) reporting that the Canadian Standards Association (CSA) has certified for sale its new state of the art SafeSite fixture for sale. Dialight reportedly designed its SafeSite fixture to replaces conventional 175W to 250W metal- halide and high-pressure sodium light sources with 100W LED technology for hazardous location applications. CSA Certification involves stringent testing and requires that all wiring be done with CSA-approved materials.

Additional features and benefits include:

Low power consumption
Universal input supply (120 - 277 VAC)
Suitable for all Class 1, Div 2, Groups A, B, C, D
hazardous environments T4A rated
Patent pending optical design
State of the art solid state lighting source
Self-contained wiring compartment eliminates
additional junction boxes
Weather/corrosion resistant lamp assembly and housing
5 year warranty
Resistant to shock and vibration
Instant on / off response
Wide operating voltage range
Power factor > .9
THD < 20%

This is more good news for anyone looking for a stand alone fixture that could be safely used indoors as LED Grow Lights. The newly approved Solid State Lighting fixture weighs 19lbs and consumes 85-115W (100W nominal) at 110 volts; for a total output of 3640 Lumens ( 70% lumen maintenance over 50,000 operating hours ). Now if they could start offering other models in different spectrums as LED Grow Lights everyone would have a happy holiday season to rejoice over.

Photonic Lattice LEDs are new class of light-emitting device

A bit older, but LEDsmagazine had reported new Solid State LED lighting technology:

Using photonic lattice technology it is possible to build large-area chips that enable ultra-high power sources for projection and other applications, writes Robert Karlicek of Luminus Devices.
The term “power LED” usually describes one of two types of LED assemblies: a conventional 1 mm2 power chip in a power package, or an array of chips (1 mm2 or smaller) combined in one of several different types of power packaging formats (semiconductor chip(s), package, encapsulant and heat sink).

While the performance of power LED devices has improved dramatically over the past 10 years, the basic concepts haven’t changed too much over the past forty years: one or more small LED semiconductor chips attached to a metal packaging structure and covered by an encapsulant/lens to help extract and shape the light output.

Conventional power LEDs have gradually evolved through incremental improvements in semiconductor and packaging materials and manufacturing processes.

Here we describe a new generation of ultra-high-power photonic lattice LEDs, which operate at input powers as high as 100 W and are orders of magnitude brighter than conventional power LEDs. These are the first commercially available LEDs using photonic crystal concepts to manage light extraction from the LED.

Now a 100W per package is impressive no doubt, hopefully this finds itself into the LED Grow Light segment soon.

LED chip maker Genesis Photonics announces new patents for white LEDs

Digitimes is reporting that:

Taiwan-based LED chip supplier Genesis Photonics yesterday debuted its latest patents on white LED technology which the company claims can produce a white LED chip without the need to combine a blue LED and phosphor.

Around two years ago, Genesis started volume production of single white LED chips using this technology with most of the products shipping to Japan, said the company. The production cost for this product is not far off from traditional blue and green LEDs. However, as the brightness of LEDs produced using this technology is still not as bright as ordinary ones, few LED makers are adopting the technology and Genesis is partnering with downstream vendors directly, stated company president Hsu Shi-Hong (transliterated from Chinese).

The company also aims for the proportion of revenues from the blue and green LED segments to reach up to 60% and 40%, respectively, in 2008, up from 45% and 55%, respectively at present, the company added. Meanwhile, the company will increase the number of its metal-organic chemical vapor deposition (MOCVD) equipment to over 25 units by the end of 2008, compared to 19 units now, noted the LED chip company.

This should be great news for the overall health of the Solid State LED lighting market, more competition in the LED Grow Light industry is always good.