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How many red 5mm leds i can power with a 12 V 1.5 A AC-Adapter?

ElectroMarco

Mar 18, 2018
3
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Mar 18, 2018
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Hi
My friend gave me 5000 red leds like this one
https://www.taydaelectronics.com/me...f78eab33525d08d6e5fb8d27136e95/a/-/a-1554.jpg
that he found in a abbandonated storage unit that he bought...

I would like to create a led sign or something , so i'm wondernig: How many red 5mm leds i can power with a 12 V 1.5 A AC-Adapter?
Do i need resistors?
If what i want to do is not possible, do you have some ideas on what can i do with 5000 leds?
 

Alec_t

Jul 7, 2015
3,581
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Jul 7, 2015
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Welcome to EP!
The number you can drive will depend on how much current each LED draws. Most LEDs like that will take 20mA ok, but you can choose a lower current and hence increase the number of LEDs used.
Yes, you will need some resistors.
Does your mains adapter provide a DC output or an AC output?
Is the output voltage regulated or not?
 

Alec_t

Jul 7, 2015
3,581
Joined
Jul 7, 2015
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3,581
This is how you could use the LEDs, arranged in strings of 5, each string having a resistor.
LED-strings.PNG
Only 2 strings are shown here.
With the resistor value shown, the LED current would be about 17mA per string, so you would be able to have 1.5A/17mA = 88 strings in theory. In practice, allowing for some margin, 80 strings should be manageable, i.e. a total of 400 LEDs.
 
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