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LED light intensity

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juststarting

New Member
First of all I would like to thank you all for the help given in the past.
Pleased to report the solar powered snail zapper is still working good. plus many other projects.
My new project is producing a hydroponic growing box, I have had good results so far,
the wave length of the 576 LEDs I have used seem good, I have plants growing and cooled them with PC fan.
It is run from a 12volt 5 amp PSU
I have two questions.
1. is there a easy way to insert some sort of a timer to switch the lights on for say 8 hours and of for 4 ?
2. how do I get a rough idea of the total light intensity,

Bazza

WHAT COULD POSIBLY GO WRONG.
 

dr pepper

Well-Known Member
Most Helpful Member
You can buy simple plug in timers to control the on time for your lamps.

If you look at the spec for your leds there will be a luminosity figure, usually in candle power or milli candle power, just add them all up to get the total, the manufacturers rating will be at a certain drive level, if your drive level is diffrent then you'd need to look at the graph on the datasheet and approximate what it would be per led.

Are/were you an existing member, I see your number of posts is only 1, but you sound like you've been here before.
 

juststarting

New Member
Yes !
understand your confusion, My old PC expired, forgot my log in details, you know the story, started again.
(think my old user name was "barmmybaz" ?

Unfortunately when I wired my contraption, I only have one input, and switched the fan, pump and lights, fortunately I have room internally,
I have been looking on Ebay for timers that run on 12v ( don't like mains power near water) but find it all a bit confusing, (I like things simple)

Thanks for your help with LEDs, I guess milli candle power = mcd.
all I know is I don't look at the array directly. ! ! ! !
you have helped me b4 remember you logo

thanks again
Baz
 
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JimB

Super Moderator
Most Helpful Member
Yes !
understand your confusion, My old PC expired, forgot my log in details, you know the story, started again.
(think my old user name was "barmmybaz" ?
Baz, would you like me to reset the password for user "Barmybaz" so that you can use that name again?

JimB
 

JimB

Super Moderator
Most Helpful Member
OK, with a bit of luck the system will send you an email with a new password.

Just one problem, I notice that "juststarting" has a different email address from "barmybaz", so you may not be using that old address any more.
If you don't receive a notification, let me know and I will define a password and send it to you in a personal message.

JimB
 

schmitt trigger

Well-Known Member
There are a couple of solutions for the timer:

1) You can purchase an exterior rated timer, which come in a sealed enclosure. I've seen a few which control irrigation water pumps, and they are completely exposed to the environment.

2) If you are proficient with programming micros or Arduinos, I would use one coupled to a RTC circuit (Like the DS1307)
 

dr pepper

Well-Known Member
Most Helpful Member
I might be inclined to hack a mains timer, as a few have a battery to keep time and a triac which powers a relay or the load direct, however you might not want to do that, you can get stuff like this:
http://www.ebay.co.uk/itm/LCD-Digit...894284?hash=item2363e6530c:g:W0IAAOSwzgRW1TN9
You might see an ac symbol on some of the ebay 12v timers, that confused me at first, but I found on one that it just means you can use 12v dc or ac power, the 230v ac rating on the one I linked is just for the contacts, 12v dc would be fine also.
Yes 1mcd means 1 milli candle power which = 0.001 candle power.
You can also use lumens, but this is largely meaningless thanks to manufacturers mis using it to overrate led brightness's.
 

juststarting

New Member
Brilliant ! ! ! Cheers dr pepper
that looks like just the thing I had in mind, it will even fit physically,
Hope to have fresh lettuce for Xmas, (sorry) will send you my second one ! !
thanks again for your help.

Baz



WHAT COULD POSSIBLY GO WRONG
 

Tony Stewart

Well-Known Member
Most Helpful Member

dr pepper

Well-Known Member
Most Helpful Member
Glad to share some useless knowledge.
 

Tony Stewart

Well-Known Member
Most Helpful Member
1 lux = 1 lumen per square meter
Take total,Lumens effectively rated and divide by effective area of full brightness.
If not avail. what LED's are used? PN?
 

juststarting

New Member
Wow that's a a lot of interesting reading vlady, didn't realise things could get so complicated, I will read and try and absorb at my leisure,
Thanks for all your suggestions about light intensity, although I don't pretend to understand it all, I guess I must be somewhere near as although my plants are in a lightless cupboard they aren't bolting and are a nice green. Most of my information came from NASA (growing plants in space)

Thank you all again for your time and trouble,

Baz

ps
JimB
got Email but can't find where to "log in"
automatically goes to "juststarting"
 
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vlady_2009

New Member
Baz, no worries. If you have any questions, just let me know and I'll try to answer/explain (which is a learning opportunity for myself, since if you can't explain something to be understandable to another person, you really don't it yourself well enough - or words to that effect by Einstein/Feynman or whoever)
Vlad
 

hyedenny

Active Member
The wrong term keeps getting used here...
LEDs are never measured in "candle power" and mcd does NOT stand for milli-candlepower!
The luminous intensity of LEDs is usually measured in mcd which stands for milli-candela.
The unit candle power, or cp, is obsolete and is approximately equal to .981 candela.
 

throbscottle

Well-Known Member
But milli-candlepower sounds sweet, like what fairies use to light their mushrooms...
Candela sounds like an artificial sweetner :woot:
 

JimB

Super Moderator
Most Helpful Member
ps
JimB
got Email but can't find where to "log in"
automatically goes to "juststarting"
Baz

I am sorry that I missed this little bit of info, it sounds as though you are automatically being logged in as "juststarting" as soon as you connect to ETO.

I suggest that you log out as "juststarting", you can do this by clicking on the "juststarting" button at the top right hand corner of the ETO page.
That will display a lot of options, one of which is LogOut, click on that.

Then you should be able to log in as "Barmybaz" using the password which was sent to you in the e-mail.

JimB
 

atferrari

Well-Known Member
But milli-candlepower sounds sweet, like what fairies use to light their mushrooms...
Candela sounds like an artificial sweetner :woot:
Candela? As usual, it depends of who and where...

Around here

a)

vela.jpeg

b)

candelam.jpg_763673443.jpg

c) Eventually, you could extend your search for Candelaria.

The fun of languages.
 

dr pepper

Well-Known Member
Most Helpful Member
Thats interesting hyedenny.
Actually I did know about the term candela, I assumed incorrectly that candela and candle power are the same.
It does seem odd 2 terms so similar are not the same.
 
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