Step down voltage from power unit

Thread Starter

circuitbuild72

Joined Oct 1, 2022
9
Hi all !

I’m new to this and am building a circuit board for a battery power pack. The output is 5V and I want to use it with both 5V & 3.2V lights. Is there a way to reduce the power output to 3.2v without adding another output which has a resistor (internal to the power pack) or adding a resistor into the 3.2v light (external to the power pack)?
 

Thread Starter

circuitbuild72

Joined Oct 1, 2022
9
Thanks for the reply @ericgibbs !

I’m using some LEDs which draw 0.02 A at 5V and some which draw the same at 3.2 V

The power pack is 1A & 5V output.

As I understand it this means the 5V / 0.02A LED’s powered by 5V / 1A power pack meansI can run up to 50 LED’s at full brightness.

I’m looking at an resistor attached to the cable for the 3.2V LED’s to step down voltage. This is as far as I’ve got, I’m a little lost in terms of if that resistor is the right way to go and how many LED’s it would power!

Any advice gratefully appreciated!
 

ericgibbs

Joined Jan 29, 2010
16,370
hi c7,
Usually with LED's the current has to be controlled, typically by using a series resistor.
eg: say your LED is White, which has a typical forward voltage of 3.2v.

So from a 5Vdc supply, if you wanted 20mA through the LED, that would require that 5V-3.2V at 20mA be dropped across the resistor.
ie 1.8V/0.02A = 90 Ohms,, a 100 Ohm resistor be OK.

Note, each LED will require its own dropping resistor.

E
 

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Thread Starter

circuitbuild72

Joined Oct 1, 2022
9
hi c72,
Welcome to AAC.
How much current for the 5v and 3.2V do you need .?
E
Thanks @ericgibbs very helpful. I can’t add resistor to each LED as I’m doing for off the shelf led strips and (long story!) can’t just replace with another type.
Is there no way to drop down the voltage to the entire set of these LED’s between the power and the LED’s?
Many thanks again
 

djsfantasi

Joined Apr 11, 2010
8,565

Danko

Joined Nov 22, 2017
1,443
Maintaining a website has quantifiable economic and other costs. One needs a reason to bear those costs. I'd be curious to know how other people who do have websites manage those costs.
My main reason was to keep resume published.
Cost: $17 per year.
 

Papabravo

Joined Feb 24, 2006
19,284
My main reason was to keep resume published.
Cost: $17 per year.
That is actually pretty reasonable. I don't know if you have retired, but that would explain why it is no longer of use to have a place for that resume. I too have abandoned my website, my blog, and my LinkedIn account since I retired in 2014. I have less than zero interest in being contacted for those purposes ever again.
 
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