led there be LED light!

[Marko]

This year I replaced fluorescent lights with led panels and I am very satisfied! I usually start tomatoes from seeds on 15 march but this year I started just two seeds one month earlier only to see if led panels do their job. Plants were under lights 6-8 hours daily, the rest of the day they were on the east facing windowsill.
This is situation on 6 march, just before transplant (should transplant them one week earlier ):


10 days later, 4 weeks after te seed was put in ground:


From my experience led ligts can not substitute sunlight, but can be very efficient additional light source. Tomatoes really grow under them. As a bonus they are cold and plants need much less watering.
I will definitively use them again next year!

[cyber5]

Originally Posted by feldon30

My problem is I perceive the flicker of A/C when I look at some LED lights on people's houses.

I think what you are perceiving is the way LEDs work, they are either on or off, they aren't good at fading in and out, at least not easily nor cost effectively right now.
I have come across a few hobbyists that are doing some really cool Xmas light type stuff with SuperBrights that will probably blossom into some type of commercial market (architectural would be my guess) by using Pulse Modulation to fade them to eliminate that off/on flicker problem.

If anyone is interested, I'm sure I have the sites bookmarked somewhere and I'll dig them out. One guy will sell you the raw materials (multi-diodes on tiny chips that you can link together easily and program via your PC). It won't be a cheap playtoy, but it might be really useful as a grow light.

[feldon30]

Exactly, they cycle on/off 60 times per second.

The solution is to have your strands of LED Christmas lights operate on DC power. Unfortunately this would increase the price by 10 fold and/or require power transformers at the end of each line which most consumers won't want to mess with.

I'm sure DC powered LED strips with amber colored caps on each bulb would look indistinguishable from old style lights. But at $20 for the power transformer and then buying linked strands, they would never sell.

[dcarch]

Originally Posted by feldon30

Exactly, they cycle on/off 60 times per second.

The solution is to have your strands of LED Christmas lights operate on DC power. Unfortunately this would increase the price by 10 fold and/or require power transformers at the end of each line which most consumers won't want to mess with.
I'm sure DC powered LED strips with amber colored caps on each bulb would look indistinguishable from old style lights. But at $20 for the power transformer and then buying linked strands, they would never sell.

60 Hz (cycles) with a half-wave rectifier. 120 Hz with a full-wave bridge rectifier.

A transformer may not be the answer. LEDs require very good voltage and current control, or they will be fried in a blink of you eye. They need complicated driver electronics.

Cheap Christmas LED lights link many of then in series with resistors to reduce voltage and current and with a diode to convert AC to DC. If you burn one light, the whole thing goes black. Resistors waste electricity and generate heat.


dcarch