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Old 01-01-2014, 05:15 AM   #16
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LED help


^ nice!
Did you use the wizard I posted a link to?

I have mine wires in 10 rows of 6 but no resistors on them yet, I will try the 4.7 ohm resistors on 7.2 volts and see how it works!
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Old 01-01-2014, 01:03 PM   #17
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LED help


For optimum efficiency, you will want as many in series as possible while still maintaining reasonable current regulation with the ballast resistors. With a 4-cell lithium ion battery, you can probably use enough LEDs in series to drop 9V and still have decent current stability. If you use 7.2V, you are totally wasting half of the power in the batteries as heat in the resistors.

You really may want to consider using a dedicated LED driver for this. You can improve the efficiency tremendously, and it would be dimmable. This would work well: http://www.ledsupply.com/led-drivers...FUiEfgodUksA2A It will take a DC input from 5 to 32V, and produce a constant-current output variable from 0-350mA at up to 48V. Your total LED load is about 5.4W, which should give you an input current to the LED driver of about 415mA at 14.4V based on 90% efficiency. That would give you a runtime of about 8.5-9 hours at full brightness, or much longer if dimmed.

With that driver, you could run three parallel strings of 20 series LEDs each, and keep the current below 180mA. With that many LEDs in each string, you would probably not need any balancing resistors. If you do (because of unequal current in the strings), they can be very small resistors that don't waste much power. You use a small potentiometer to adjust the current setting. You can use two potentiometers together to have a dimming control and a maximum-current limit (since the full 350mA would burn out your three LED strings).

And on another note, you may want to consider better LEDs. Six of these: http://www.superbrightleds.com/morei...ngle/653/1281/ would produce way more IR output than all 60 of your leds, with about the same power consumption. You can run all six of them in series on this driver: http://www.ledsupply.com/led-drivers...r-with-dimming, with a single pot for dimming control.
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Last edited by mpoulton; 01-01-2014 at 01:21 PM.
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Old 01-01-2014, 02:20 PM   #18
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LED help


Oh wow! I'm going to try that also!

Greap help guys!

Happy new year!
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Old 01-01-2014, 02:33 PM   #19
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LED help


quick question about the LED's you said to use, since those have 4 wire spots how do i run those series? just use one positive and one negative??

Last edited by k20crx; 01-02-2014 at 04:17 AM.
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Old 01-01-2014, 05:49 PM   #20
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i ordered the 6
https://www.superbrightleds.com/more...ngle/653/1281/

and this
http://www.ledsupply.com/led-drivers...r-with-dimming

and this for dimming
http://www.ledsupply.com/led-drivers...-potentiometer

seems WAY easier then having a load of solder points on a perf board!

Last edited by k20crx; 01-02-2014 at 04:16 AM.
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Old 01-02-2014, 09:44 AM   #21
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LED help


Perfect. Way easier. Be sure to use a good heatsink for those LEDs. A CPU heatsink (probably without the cooling fan) would be a good choice, or a flat bar of aluminum. The cooler you keep them, the more efficient they will be and the longer their lifetime.
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