Having trouble figuring out meaning of Buck Regulator voltages.

Thread Starter

sirchuck

Joined Feb 14, 2016
131
So I want some cheap 3.3v fixed output buck converters and I found this, but I don't understand their description of how the voltage works, do you?

They show on the back 3.3v then 5v under that, then 9v and 12v under that????

The product:
https://www.ebay.com/itm/10pcs-DC-DC-Step-Down-Buck-Power-Supply-Module-5V-28V-to-3-3V-3A-Fixed-Output/362479943334?hash=item54657cfea6:g:bLoAAOSwUqVb4WWR:rk:14:pf:0

I attached the pertinent image.


Bonus: I also see sometimes buck converters on Amazon give two input voltages??? Like:
5v Regulator, DROK 5pcs Mini Voltage Reducer DC 4.5-24V 12V 24V Step Down to 5V Buck Converter Board 3A Volt Step-Down Transformer Power Supply Module

The output should be 5v, but it gives 3 input voltages? (4.5-24v) (12v) (24v) that makes no sense.


Thanks in advance. :D
 

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Thread Starter

sirchuck

Joined Feb 14, 2016
131
I still don't get it.

You're saying the fixed output is not fixed, it's configurable?

I'm really having trouble figuring out how that image I linked is supposed to help me. Is it saying, for example, the top left pair of leads is for 3.3v output and the top right is for 5v output, and the bottom left is for 9v output and the bottom right is 12v output?

The way I see it, the right side is your input, and the left side is your output. I should be able to plug in 5v-28v on the right and pull out 3.3v on the left.

The second product itself isn't important, lots of them read with multiple voltages for input which I think is weird if it says 4.5-24v then why should they also tell me 12 for input? It seems like that's already covered by the 4.5-24v


Second product link:
https://www.amazon.com/Regulator-DROK-Converter-Step-Down-Transformer/dp/B0758ZTS61/ref=sr_1_fkmrnull_1?keywords=5v+Regulator,+DROK+5pcs+Mini+Voltage+Reducer+DC+4.5-24V+12V+24V+Step+Down+to+5V+Buck+Converter+Board+3A+Volt+Step-Down+Transformer+Power+Supply+Module&qid=1551642551&s=gateway&sr=8-1-fkmrnull
 

spinnaker

Joined Oct 29, 2009
7,837
I still don't get it.

You're saying the fixed output is not fixed, it's configurable?

I'm really having trouble figuring out how that image I linked is supposed to help me. Is it saying, for example, the top left pair of leads is for 3.3v output and the top right is for 5v output, and the bottom left is for 9v output and the bottom right is 12v output?

The way I see it, the right side is your input, and the left side is your output. I should be able to plug in 5v-28v on the right and pull out 3.3v on the left.

The second product itself isn't important, lots of them read with multiple voltages for input which I think is weird if it says 4.5-24v then why should they also tell me 12 for input? It seems like that's already covered by the 4.5-24v


Second product link:
https://www.amazon.com/Regulator-DROK-Converter-Step-Down-Transformer/dp/B0758ZTS61/ref=sr_1_fkmrnull_1?keywords=5v+Regulator,+DROK+5pcs+Mini+Voltage+Reducer+DC+4.5-24V+12V+24V+Step+Down+to+5V+Buck+Converter+Board+3A+Volt+Step-Down+Transformer+Power+Supply+Module&qid=1551642551&s=gateway&sr=8-1-fkmrnull

Says it right here.

Output Voltage: Integrated adjustable and fixed output (Adjustable range is 0.8-17V, fixed output are 1.8V, 2.5V, 3.3V, 5V, 9V, 12V that can be chosen on the back side)


I don't see how it could be more clear. You first decide ahead of time if you want fixed or variable. If you pick fixed then you configure for which fixed voltage that you want and it remains fixed.

Input voltages are such
Input Voltage: DC 4.5-24V

I am guessing this is not also a boost regulator so if you want 12V out fixed you will need to supply something above that.
 

spinnaker

Joined Oct 29, 2009
7,837
This is how you get the fixed voltage.

Output integrated adjustable and fixed voltage, you can get fixed output voltage by soldering the pot on the board. If the fixed output voltage is not what you want, you can adjust it by potentiometer.
 

mvas

Joined Jun 19, 2017
538
10pcs DC-DC Step Down Buck Power Supply Module 5V-28V to 3.3V 3A Fixed Output
https://www.ebay.com/itm/10pcs-DC-DC-Step-Down-Buck-Power-Supply-Module-5V-28V-to-3-3V-3A-Fixed-Output/362479943334?hash=item54657cfea6:g:bLoAAOSwUqVb4WWR:rk:14:pf:0

I still don't get it.
You're saying the fixed output is not fixed, it's configurable?
Yes the output voltage is fixed at 3.3 volts.
Yes, it is configurable by the manufacturer
The output Voltage of that circuit board is configurable, by the manufacture, by simply changing the resistors on the board.

I still don't get it.
I'm really having trouble figuring out how that image I linked is supposed to help me.
Is it saying, for example,
the top left pair of leads is for 3.3v output
the top right is for 5v output
bottom left is for 9v output
the bottom right is 12v output?
No.
I repeat .... the output voltage of that circuit board For Sale is fixed at 3.3 Volts
But the output voltage of that board can be changed ( reconfigured ) to 5v, 9v or 12 v, IF AND ONLY IF,
the manufacturer ( or you ) replace two resistors on the circuit board.
 

dendad

Joined Feb 20, 2016
3,084
Think of it as buying a car, available in many colors. But, you have to choose the specific color when you order the car. Once you get it, the color IS changeable, but not without some effort, like respraying it.
In this case, you can change the voltage as the board is designed with that in mind, but it does require a mod to component values.
I use a few of these and they have a setting pot...
3A buck converter.jpg
 

Thread Starter

sirchuck

Joined Feb 14, 2016
131
Perfect, that makes so much more sense now. I saw all the numbers on the PCB and 4 different places to connect wires to and thought maybe they were different outputs.

I realize the page said it was 3.3v fixed of course, but I didn't understand what the actual bord was saying, but thanks all I get it now.
 
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