High Efficiency LED for Joule Thief, etc.

[Cherryman]

Hi everyone,

if someone would be ready to buy 2 of either style of the below LED Grow lights to be sent to a Joule Thief Guru like TK or LaserSaber so one can be moded and the other kept original in order to test how much power can be saved and still be able to grow a plant hopefully at the rate as the non moded one, that would be of great service.

Box light: http://www.ebay.com/itm/300W-LED-Grow-Light-Hydroponic-Plant-Veg-Flower-Full-Spectrum-Panel-Lamp-/301507617587?hash=item4633412333
or: http://www.ebay.com/itm/MarsHydro-300W-LED-Grow-Light-Full-Spectrum-Panel-Indoor-Medical-Plant-Veg-Bloom-/171620287365

Strip light: http://www.ebay.com/itm/Waterproof-81w-LED-Grow-Light-Strip-Red-Blue-Bar-Hydroponic-Indoor-Plant-Lamp-/301663638915?

Please post if you are ready to do this or if you want to stay private send me a PM.

Thanks for your help

Luc

Hi GotoLuc,

Those box LED grow light usally use when measured out of the box around 180 Watts  , a frend of mine uses them.

I myself have ordered some 80W grow lights ( from China ) and they use around 43W out of the box.
http://www.aliexpress.com/store/product/2pcs-lot-E27-E40-80W-640Red-160Blue-Hydroponics-Plant-Lighting-85-265V-LED-Grow-Light-free/835980_1699470283.html

Just wanted to share the info.  Because i too want my indoor aquaponics be capable of running solar.

[TinselKoala]

Yes, the issue of interest here is the practical application of the light from these LEDs. Simple illumination is one thing, but there is presently considerable interest in indoor hydroponic farming, using LEDs for plant growth when sunlight isn't available. So here's where what we've learned about LEDs and Joule Thieves starts coming into play.
MarkE is of course right that the standard JT is mostly for allowing use of the residual energy in depleted batteries, or running LEDs from other low-voltage sources. But we've learned from JTs that LEDs can be "overdriven", that is, driven in pulse mode at higher than the nominal continuous DC drive, and can produce even brighter momentary light pulses, so that the LED seems exceptionally bright to the human eye.
So, instead of JTs running at low input voltages, let us consider whether ordinary pulse-width modulation, overdriving the LED for small duty cycles, can produce any effects, like maybe improved yield/power ratios, when used for plant growth. Would there be any efficiency gain, for example, by driving a bank of LEDs at a high frequency 50 percent duty cycle, at higher than normal drive currents (with another bank phased 180 degrees perhaps, so that the plants would see "continuous" light)?

[MarkE]

Yes, the issue of interest here is the practical application of the light from these LEDs. Simple illumination is one thing, but there is presently considerable interest in indoor hydroponic farming, using LEDs for plant growth when sunlight isn't available. So here's where what we've learned about LEDs and Joule Thieves starts coming into play.
MarkE is of course right that the standard JT is mostly for allowing use of the residual energy in depleted batteries, or running LEDs from other low-voltage sources. But we've learned from JTs that LEDs can be "overdriven", that is, driven in pulse mode at higher than the nominal continuous DC drive, and can produce even brighter momentary light pulses, so that the LED seems exceptionally bright to the human eye.
So, instead of JTs running at low input voltages, let us consider whether ordinary pulse-width modulation, overdriving the LED for small duty cycles, can produce any effects, like maybe improved yield/power ratios, when used for plant growth. Would there be any efficiency gain, for example, by driving a bank of LEDs at a high frequency 50 percent duty cycle, at higher than normal drive currents (with another bank phased 180 degrees perhaps, so that the plants would see "continuous" light)?

Being diodes, the power dissipated by an LED can be approximated as:

P_DISSIPATED = DC*V_FW*I + DC^0.5*I²*R_FORWARD
P_DISSIPATED = V_FW*I_AVE + DC^0.5*I²*R_FORWARD

Since the light output is almost exactly proportional to I_AVE, and

P_DISSIPATED = K*P_OUT + DC^0.5*I_PEAK²*R_FORWARD

And since I_PEAK = I_AVE/DC:

P_DISSIPATED = K*P_OUT + DC^-0.5*I_AVE²*R_FORWARD

So, you want to minimize the term on the right you want DC to be as large as possible:  ideally 1.0.

LEDs can be dimmed by PWM or by setting the current.  TI and Linear Technology took different approaches for different reasons.  TI built parts that varied the current while Linear Technology used PWM.  TI argued for maximum efficiency.  Linear Technology argued for most uniform color across brightness.

[gotoluc]

Hi GotoLuc,

Those box LED grow light usally use when measured out of the box around 180 Watts  , a frend of mine uses them.

I myself have ordered some 80W grow lights ( from China ) and they use around 43W out of the box.
http://www.aliexpress.com/store/product/2pcs-lot-E27-E40-80W-640Red-160Blue-Hydroponics-Plant-Lighting-85-265V-LED-Grow-Light-free/835980_1699470283.html

Just wanted to share the info.  Because i too want my indoor aquaponics be capable of running solar.

Thanks for sharing Cherryman,

those look to be a great deal. So if anyone can buy 2 of these for the price of one I was suggesting I'm sure it would be good enough for TK to make some tests.

No offers yet and hopefully the drop in price will help get a sponsor.

Luc

[tinman]

Yes, the issue of interest here is the practical application of the light from these LEDs. Simple illumination is one thing, but there is presently considerable interest in indoor hydroponic farming, using LEDs for plant growth when sunlight isn't available. So here's where what we've learned about LEDs and Joule Thieves starts coming into play.
MarkE is of course right that the standard JT is mostly for allowing use of the residual energy in depleted batteries, or running LEDs from other low-voltage sources. But we've learned from JTs that LEDs can be "overdriven", that is, driven in pulse mode at higher than the nominal continuous DC drive, and can produce even brighter momentary light pulses, so that the LED seems exceptionally bright to the human eye.
So, instead of JTs running at low input voltages, let us consider whether ordinary pulse-width modulation, overdriving the LED for small duty cycles, can produce any effects, like maybe improved yield/power ratios, when used for plant growth. Would there be any efficiency gain, for example, by driving a bank of LEDs at a high frequency 50 percent duty cycle, at higher than normal drive currents (with another bank phased 180 degrees perhaps, so that the plants would see "continuous" light)?

Remember this one TK ?

https://www.youtube.com/watch?v=hvf9Uo7UVx0