Is this LED diagram right?

sillyface · Post by **sillyface** » Thu May 11, 2006 3:05 am

Hi all
After reading the forums and learning from the links, I've managed to draw up a LED circuit diagram to light my beloved Enterprise D.
However, before I go down to Maplins (Radio Shack) and spend money and time on the risk that everything will blow, is there anyone out there that can cast their experienced eye over my diagram, I would be so grateful.........

http://i58.photobucket.com/albums/g240/ ... iagram.jpg

macfrank · Post by **macfrank** » Thu May 11, 2006 10:25 am

The design looks OK, but you're overdriving the LEDs slightly. You can use the LED Calculator to find the optimum arrangement for each section; it came up with layouts that used slightly less power overall.

jwrjr · Post by **jwrjr** » Thu May 11, 2006 11:19 pm

macfrank is correct. Most leds max out at 25 ma, and it is better to calculate the resistors at 20 ma. Why? because unless it is regulated (costs more), a 12 volt ac adapter doesn't put out 12 volts. The average 12 volt ac adapter can put out as much as 15 volts unless it is loaded down to a large fraction of its capacity. You don't want to load it down by onerdriving your leds.

Sparky · Post by **Sparky** » Fri May 12, 2006 7:25 am

Even if your 30 mA for the red is correct, the resistor is to small it needs to be 240 ohms or greater, rounding down will be driving the Reds harder as was mentioned.

Same with the Whites (and Blues we assume wants 3.4 volts, reverse voltage is not used in the calculations, its just a warning, if you hook it up backwards to more than 5 volts its a goner) my calculation shows 173 1/3 ohms, the resistor listed is to small.

It looks like the math was wrong, the resistor values were all smaller than what I get over here.

Remeber to round up to the nearest available resistor value, rounding down delievers to much power to the LED's.

sillyface · Post by **sillyface** » Sat May 13, 2006 8:42 am

Cheers.
I'll have another go at it.

sillyface · Post by **sillyface** » Mon May 15, 2006 8:46 am

Right...I decreased the voltage to a non life threatening 9V and pulled back the amps to a gentle 20mA (Don't want to blow up the Enterprise or the Borg will invade earth)

and I've double checked my ohms law calculations..

Have I got this right

http://i58.photobucket.com/albums/g240/ ... ramMk2.jpg

macfrank · Post by **macfrank** » Mon May 15, 2006 9:39 am

All the values seem OK. The LED calculator (http://led.linear1.org/led.wiz) can give you other resistor values and options.
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