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Old 03-07-2007, 07:26 PM  
RedShoe
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Join Date: Feb 2001
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Quote:
Originally Posted by rowan View Post
Oh yeah, with regards to you using a 9V battery... if you're supplying 40 LEDs then it's unlikely it will last long. 40 LEDs at 10 milliamps each is a total draw of 400 milliamps (0.4A), and if you want more light you could probably go up to 30mA each which is 1.2A. I did a quick search and found a 9V rechargeable battery rated at 400 milliamp hours (0.4 amp hours), which means - in theory - it can supply 400 milliamps for an hour, 200 milliamps for two hours, 100 milliamps for four hours etc. Your 9V battery would probably provide useable output for less than 10-15 minutes, assuming it was even able to discharge at a 1.2A rate.

That's why D cells are bigger than AA; they have the same voltage, but they will last longer and/or provide a higher current.
Rowan,

I did it the way you have in your 2nd drawing. I drilled 80 holes. I put in two LEDs, and soldered the + of on and the - of the other together. Then I soldered a resister to the end of the series of 2. I did that 20 times.



I hooked up a 9v and to see how long it would last I ran a test. (I didn't know the math so I did it the only way I knew how) I hooked up a 9v and just left it on. I checked it every 10 minutes for the first 2 hours, then popped in "The God's Must Be Crazy II" and it was still on and bright at the end of that movie. And the battery was cool to the tough. I was afraid I'd burn out the battery.
I dunno know why.. I just thought I would.

It's for a camera so I figured 2 hours should be more than enough to film. I can shoot a scene in just a couple of hours.

I think next I'll try to incorporate a rechargeable system so all you need to do is plug it in for a few hours before you shoot.
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