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Change Pot in Mini Buck Converter

ThomsCircuit

Active Member
Heh....yeah....the 70's....:hilarious::joyful:
:joyful:
One of my fav shows. "Marsha, Marsha, Marsha"
Ive got some white smd leds (FV=2.8-3.2). Want to add them to the input and output. how would i do this when the voltage can vary from 4.5-24v input and 3-21v output?
 

ThomsCircuit

Active Member
I thought you were using a digital display? why would you need an indicator?
i am. i just saw in on a converter and wondered how it was done. I did try looking it up but could not find any definitive information. I also purchased a few dozen about a month ago and thought this would be a good project to use them in.
 

eTech

Well-Known Member
i am. i just saw in on a converter and wondered how it was done. I did try looking it up but could not find any definitive information. I also purchased a few dozen about a month ago and thought this would be a good project to use them in.

Doesn't make sense, but anyway...

Use a simple constant current source, like a current mirror. The load would be the LED.
 

ThomsCircuit

Active Member
Doesn't make sense, but anyway...

Use a simple constant current source, like a current mirror. The load would be the LED.
I see it here on this module. The input and output voltage is variable. I recognize all of the components. My design has most of these except for the two diodes. It just appears that the LED has just a resistor and nothing else restricting the current.
1647494500730.png
 

eTech

Well-Known Member
Use something like this current limiter.
The LED current is a constant 10mA and varies slightly over the whole voltage range.

1647495716408.png
 

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