Hi Psy,
Looking over the photo images, I believe you are correct, they are Boost module.
Did you reorder for Buck?
I prefer the terms Step up or Step down names.
E

 

Hi Psy,
Looking over the photo images, I believe you are correct, they are Boost module.
Did you reorder for Buck>
I prefer the terms Step up or Step down names.
E

Yeah, me too. Step Up and Steup Down are more intuitive.
Yes, I got the refund from Aliexpress and already ordered a Buck converter aka Step Down, or at least so I hope. I bought this one:
https://www.aliexpress.com/item/4001080770461.html

 

I just got the step-down converter. Almost 1.5 months later!

But I already have a question and hope I didn't break it already. lol

I connected my external power supply to the input leads of the converter, set the power supply to 25V and 1A current limit.
Then, I measured the output of the converter to adjust voltage to 10V.
Then, I connected a 9Ω load (5Ω - 4W and 4Ω - 5W resistors) to see if the loads were heating up. They were, slowly but they were.
Then I switch my DMM to current mode and directly measured current at the output of the converter and the converter have a led that when power is on, it turns blue. Then, when was adjusting the current, at some point, the led turned red. But after this, the led never turned back to blue!

Is this a bad sign?
I couldn't understand this description in the Aliexpress page of the item:

6 - Turn Lamp Current: Constant Current Value * (0.1), turn the lamp current and constant value linkage, such as constant current value is 3.0A, turn the current lamp is set to a constant current is 0.1 times (0.1 * 3A = 0.3A)

I can't understand a single word in this paragraph. Could anyone please explain to me?