Home | Community | Message Board


RVF Garden Supply
Please support our sponsors.

Cannabis, Marijuana, Ganja & Greens >> Cannabis Cultivation

Welcome to the Growery Message Board! You are experiencing a small sample of what the site has to offer. Please login or register to post messages and view our exclusive members-only content. You'll gain access to additional forums, file attachments, board customizations, encrypted private messages, and much more!

Amazon Shop for: HPS

Jump to first unread post. Pages: 1
Offlineomentheduck
Male


Registered: 06/01/08
Posts: 18
Last seen: 7 years, 7 months
Help With lIghting
    #193255 - 02/08/09 03:01 AM (7 years, 9 months ago)

*Charts below.

This is a real easy way to find the number of Lumens Per Square Foot (Foot-Candles) you are getting from your bulb at any distance. It’s the same value you’d get using the more complicated formulas below, but is real quick and simple.

    * Multiply the lumen output of the bulb by 45.84.
    * Divide by the number of inches from the bulb squared.

It’s that simple.

This would be based on the use of a typical 120° reflector. If the reflector cast a different angle, then we would need to manipulate the formula a bit as is shown below. It’s all based on spherical geometry.


This is the longer detailed formulas for calculating the number of Foot-Candles (Lumens/ft.²) coming from a bulb:

The divisor must be equal to the actual area that is being illuminated by the bulb, which is not based on your floor plans. The divisor in Formula A is calculating a spherical propagation of light, which is what the light is really illuminating.

Formula A:
Foot-Candles = Lumens ÷ (4 × Pi × d²)

Where:
d = The distance from the bulb in feet.
Pi = 3.14159

If you wanted to know how many Foot-Candles of light are striking your plant 10" away from a 400 watt HPS  that puts out 50,000 lumens you would do this:

Foot-Candles = 50000 ÷ (4 × Pi × (10/12)²)
Foot-Candles = 50000 ÷ (12.57 × 0.6944)
Foot-Candles = 50000 ÷ ( 8.729)
Foot-Candles = 5,728

So, there are 5,728 Foot-Candles of light hitting your plant 10" from a 400 watt HPS  with no reflector.

Now, because we are using reflectors it will actually be more. Let's calculate how many Foot-Candles hit your plant 10" away with a typical 120° reflector.

Formula B:
Foot-Candles = Lumens ÷ (2 × Pi × d² × (1 - cos(A/2)))

Where:
A = The degree of the reflector. (Most of us have 120° reflectors)
d = The distance from the bulb in feet.
Pi = 3.14159

To make this easier we already know the value of d² when the distance is 10" from the bulb. That value as calculated above is 0.6944.

Foot-Candles = 50000 ÷ ( 2 Pi × d² (1 - cos(120/2)))
Foot-Candles = 50000 ÷ ( 2 Pi × d² (1 - cos(60)))
Foot-Candles = 50000 ÷ ( 2 Pi × d² (1 - 0.5))
Foot-Candles = 50000 ÷ ( 6.283 × 0.6944 × 0.5)
Foot-Candles = 50000 ÷ (2.181)
Foot-Candles = 22,918

So, you would get 22,918 Foot-Candles (Lumens/ft.²) of light 10" away from a 400 watt HPS  using a 120° reflector.

The picture below is a Blaze main cola  that is 16" long. It is 10" from a 1,000 watt HPS . This HPS  puts out 140,000 lumens. The illuminance in the units of Foot-Candles (Lumens/ft.²) are marked and labeled with the distance in inches from the bulb. You'll see the bottom of the cola  is getting the illuminance of equatorial sun.



Disclaimer: This post was intended to simply show the wide range of illuminance that indoor plants endure when using lights. The typical rules of thumb are still the best way to calculate your lighting needs. Here are a few:

*Using 60 - 100 watts per square foot of HID  lighting will provide enough light to bring out the best in the genetics that you're growing, provided that you don’t grow the plants over 3 feet tall. If you do it’s not a problem, you just won’t get bud at the bottom of the plants.

*Keep lights close to the plants to provide penetration to lower branches.

*Air cool reflectors to dissipate the heat so that the only concern you'll have on the distance of your light to the top of the plants will be the amount of light.

*Don't put 400 watt HPS  lights any closer than 7 inches from the top of the plants regardless of temperature.

*Don't put 1,000 watt HPS  lights any closer than 12 inches from the top of the plants regardless of temperature.

In other words, my plant above is too close to the light and you can see how it’s turning color at the very top.





I made the first graph, which was the Foot-Candles for an HPS  bulb, on August 5, 2004. I could never find accurate graphs for PAR lumens, so I just made them myself. The graphs are based on pure geometry and physics.


To make the graph, you first need to calculate the number of Foot-Candles that you’d get from any distance from the bulb. This is shown above.

After calculating the number of Foot-Candles, a conversion is used to find the number of micromoles per square meter per second (umol/m²/s) of irradiance within the frequencies 400nm – 700nm (PAR).

The conversions are as follows:
The conversion is a multiplier.

High Pressure Sodium - 0.131
Metal Halide - 0.152
Sun – 0.199

After finding the PAR irradiance I just compared it to the 1,990 umol/m²/s we get from the sun by dividing by that value and showing the values as a percentage.







None of this is mine nor did I alter anything! This is just something I think that might help It has help me and i wanted to share and help!
all credit must go to caligrower


--------------------
"I look, therefore I see. I try, therefore I will. I embrace, therefore I'm embraced. I believe, therefore I am!" omentheduck


Post Extras: Print Post  Remind Me! Notify Moderator
OfflineNibin

Registered: 04/20/08
Posts: 21
Last seen: 7 years, 9 months
Re: Help With lIghting [Re: omentheduck]
    #193267 - 02/08/09 04:23 AM (7 years, 9 months ago)

Have you thought about including this as a writeup in the main site?

You can create documents of your own in the main site.


Post Extras: Print Post  Remind Me! Notify Moderator
Offlineomentheduck
Male


Registered: 06/01/08
Posts: 18
Last seen: 7 years, 7 months
Re: Help With lIghting [Re: Nibin]
    #193296 - 02/08/09 01:31 PM (7 years, 9 months ago)

yea but it's not mine, just sharing it. thank you tho.


--------------------
"I look, therefore I see. I try, therefore I will. I embrace, therefore I'm embraced. I believe, therefore I am!" omentheduck


Post Extras: Print Post  Remind Me! Notify Moderator
Jump to top. Pages: 1

Amazon Shop for: HPS

Cannabis, Marijuana, Ganja & Greens >> Cannabis Cultivation

Similar ThreadsPosterViewsRepliesLast post
* Northern Lights & Haze stopped growing-first time post fearlessfly51 1,419 4 05/04/09 07:37 PM
by fearlessfly51
* UVB Lights
( 1 2 3 all )
coda 34,219 57 06/02/13 02:23 PM
by Hawksresurrection
* HID lights DON'T use a lot of power!
( 1 2 3 4 5 6 7 all )
Hanky 80,965 120 08/16/14 01:02 PM
by Guy Fawkes
* Can a Seedling get too much light?
( 1 2 3 all )
agmotes165 21,247 45 06/21/09 09:31 AM
by agmotes165
* What Stuff Will I Need for Lighting FugueRider 1,275 11 05/15/09 11:19 AM
by Dr. Siekadellyk
* About Lights Picklez 4,181 1 07/04/09 02:30 AM
by captainmurphie
* 18 vs 24 Hours of Light in the Vegative Cycle
( 1 2 3 all )
erb 10,633 51 05/12/09 06:33 PM
by Yrat
* Lighting Question Chronica 1,238 4 10/06/08 12:59 AM
by tenacioustornado

Extra information
You cannot start new topics / You cannot reply to topics
HTML is disabled / BBCode is enabled
Moderator: FurrowedBrow, Magash, Dr. Siekadellyk, phychotron
1,364 topic views. 1 members, 32 guests and 25 web crawlers are browsing this forum.
[ Toggle Favorite | Print Topic | Stats ]
Search this thread:
Seedsman.com
Please support our sponsors.

Copyright 1997-2016 Mind Media. Some rights reserved.

Generated in 0.057 seconds spending 0.003 seconds on 14 queries.