basic led setup.

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Old 08-21-20, 04:57 PM
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basic led setup.

ok, so i am making a 1/350 scale uss enterprise. And am lighting the hangar dec, flight deck and the tower. With led lights. I have 5mm led diodes that range in color and voltag is 3.2v. I will have 7 white leds I would like to do in parallel. 3 blue all individual and 2 sets of 3 white. And another set of 4 white. I also want to do them all of one power supply I would like to be able to use 2 9 volt batteries and wall power and switch between the 2 if i need. I am just really confused with all this stuff and trial and error has led to burnt leds, dim leds that were just full brightness and confusion. Thank you all.
 
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Old 08-21-20, 05:23 PM
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LED chips in parallel are trouble to design. U need to be thinking of current sources, not voltage. So, is the rating 2mA or 20 or ?
 
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Old 08-21-20, 05:38 PM
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Need more info to help you. Please provide the manufacturer and part numbers of the diodes, power supply and battery you are using. If I read your post correctly you have 16 diodes. If the diodes are different besides color, indicate which make up the group of 7, two groups of 3 and the 3 singles. Also provide the schematic for the circuit that resulted in burnt LEDs.
 
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Old 08-21-20, 06:38 PM
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The led are 20 mA. I don't have a power supply yet, i do need to get one.https://www.amazon.com/gp/aw/d/B073Q...b_b_asin_title
here are the exact led.
I'll try to get an schematic
 
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Old 08-21-20, 07:05 PM
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here is my plan



here is what is giving me dim leds but was giving me bright leds
 
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Old 08-21-20, 07:12 PM
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u r showing constant voltage sources. These will not work. Be thinking in the current domain, not voltage.
 
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Old 08-21-20, 09:06 PM
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Welcome to the forums.

In your bottom diagram.... you have 7 LED's in series. That would require a +/-20v supply as each diode requires 2-3v. As a hobbyist.... it may be easier to use smaller parallel strings and resistors. The value of the resistor can be computed but it depends on what each LED requires as different colors require different currents.

I would get some assorted 1/2w values like 100, 180, 240 ohms and try them experimentally. Each string would need a 100 ohm minimum and you can add resistance so that the strings would be different brightness.
 
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Old 08-22-20, 06:08 AM
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Since these R/Y LEDs operate at 2 vdc and these B/G/W LEDs operate at 3vdc, select a resistor that provides 2vdc to the circuit if both voltage LEDs are in the same circuit. If the 3 vdc LED is not bright enough, create a separate circuit with its own resistor. The minimum wattage (watts) of the resistor in PJmax's circuit is voltage drop (volts) times number of LEDs in circuit times .020 (amps).
 
 

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