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nobicus
Starting Member
United Kingdom
20 Posts |
 Posted - 02/01/2008 : 08:38:25
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How many LEDs can I run off a 12 volt battery? How long would an 80 amp hour battery last with, say, 200 LEDs running off it.
There is a company on ebay selling growlights made up of banks of red and blue LEDs but these are 110 volt. Thought I could make my own and run it off a 12 volt supply (looking for yet more excuses to actually build a windmill to convince she-who-must-be-obeyed that there is good reason for me playing in the shed!)
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gotwind
Forum Admin
United Kingdom
1013 Posts |
Posted - 02/01/2008 : 13:57:40
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Ghurd is the LED master.
You can run as many led's as you want in strings of probably 3 with a resistor.
Ghurd suggests running leds at lower than rated current levels, 15mA as I recall.
Therefore 200 x 15mA = 3 amps
80Ah/3A = 26 hours on full battery.
Hopefully Ghurd or Fungus will add to this discussion.
Ben.
The Futures Green - Getwind of it. |
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fungus
Moderator
302 Posts |
Posted - 02/01/2008 : 14:08:58
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| Ben is right but you only really want to use 20% of the battery for long life so I would say around 5 hours if you'll be using it regularly. |
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nobicus
Starting Member
United Kingdom
20 Posts |
Posted - 02/01/2008 : 15:04:12
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| This is great! I can look to wind charging my battery on a continuous basis and using the grow lights overnight. Can I use the photocell out of the garden lights that are referred to in the postings about charging AA batteries to switch the LEDs on and off? |
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gotwind
Forum Admin
United Kingdom
1013 Posts |
Posted - 02/01/2008 : 15:33:42
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You could use the circuit I guess, but switching 3 amps is going to need a relay I would expect.
I'm no expert in this area, thankfully there are others that will chip in...
Here is just the thing at Maplin £6 - pdf also available for full spec
http://www.maplin.co.uk/module.aspx?ITAG=SPEC&ModuleNo=28574&doy=2m1#spec
The Futures Green - Getwind of it. |
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ghurd
Junior Member
USA
326 Posts |
Posted - 02/01/2008 : 19:38:52
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The math is off a bit. 3 LEDs in series with 1 resistor.
And 67 strings of 3 LEDs is 201 LEDs. 67 X 0.015 = 1A
And red LEDs can run 4 in a string with 1 resistor.
25 strings of 4 red LEDs = 100 red. 25 strings at 15ma each = 0.375A.
33 strings of 3 blue LEDs = 99 blue. 33 strings at 15ma each = 0.495A.
Thats 0.87A for 199 LEDs.
80AH x 25% = 20AH (what I'd use). 20AH/0.87= 23 hours.
There are a few simple circuits around for making it automatic, and a mosfet would be a better choice than a relay IMHO.
LM741 and CDS cell (LDR) should get a lot of google hits.
Like these... Replace the relay with the LEDs, change the transistor to a power fet. Change resistors etc where needed.
http://pagesperso-orange.fr/e-lektronik/LEKTRONIK/RP303.htm
http://www.uoguelph.ca/~antoon/circ/sensor2.htm
Warning: While googling the same as above, I got the virus from hell from a site in Italy.
G-
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gotwind
Forum Admin
United Kingdom
1013 Posts |
Posted - 02/01/2008 : 19:57:41
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Thanks Ghurd for the Math correction.
Hope the virus didn't effect your system too badly, hopefully your anti virus software picked it up.
Ben. |
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ghurd
Junior Member
USA
326 Posts |
Posted - 02/01/2008 : 20:22:25
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The anti-virus picked it up instantly, but as low threat spyware. In 10 minutes the machine was completely shot.
Lost everything.
The spyware searched out viruses to down load. Got like 40 viruses in 5 minutes.
Tried maybe 10 "Get Rid of It" programs. Nothing got the main problem out.
Wife knows about that stuff, and no... she wasn't pleased.
Couldn't get it out of the system. Even with a few complete reformats. Took 2+ weeks.
Had to buy a $50 program that completely overwrote the HD with random 1's & 0's 3 times. Then it worked.
Then it took another week getting her fancy programs back in and set up.
Had to buy a VISTA laptop for the inbetween down time time. Vista sucks.
I'm only allowed to use MY laptop now, not her good machine.
So don't go to Italian sites related to LM741.
Or your wife will make you use Vista.
G- |
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ghurd
Junior Member
USA
326 Posts |
Posted - 02/01/2008 : 23:44:47
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Plants want a couple certain spectrums. Not sure what they are, but I would google it before I bought the LEDs.
They want a certain lenght of dark time too. 7 hours sticks in my mind for some reason. Not sure.
G- |
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nobicus
Starting Member
United Kingdom
20 Posts |
Posted - 03/01/2008 : 08:10:37
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Even more thanks than before. Sorry about the virus. Had a bad one once - stupid but I felt like I'd been raped. I am now rather paranoid about anti virus software. I like belt, braces, string, rope and hands in pockets too.
Again many thanks for the LED stuff. |
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fungus
Moderator
302 Posts |
Posted - 03/01/2008 : 10:25:56
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| simple fix - dont use windows ... |
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Topic |
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LEDs
