Dc-dc adjustable step-down module 5a 75w - not working

1

Hi,
I have ordered and received 12 of these useful boards for a large LED string project. Unfortunately, I have tested 5 so far and only one is actually adjusting from a 12v DC supply to 5v. The others are simply passing the 12v through.
Am I doing something wrong or have I struck a bad batch?
Unfortunately I have run out of time and need to solve this another way tomorrow. Frustrating.
cheers
David

5 Likes
2

Hi David,

Welcome to the forum, though sorry to hear you’re having issues.

Just to confirm, are these the step down converters you’re referring to?

You will need to adjust the voltage output using a multimeter while adjusting the voltage potentiometer. Have you double checked you’re adjusting it in the right direction? And that you haven’t hit the limit in the wrong direction?

If you haven’t set the output voltage limit below your input voltage then yes, they will essentially just pass your input voltage straight through with only a small drop.

4 Likes
3

Yes, I have. I thought I might be doing it wrong but I have found one that is working in the 5 so far. I try both pots in both directions.

I will try some more. How many turns do I have to do before I know I am either end?

cheers

5 Likes
4

Hi David
You will hear a faint “clicking” noise when the pot gets to the end of the travel. They are multi turn pots (10 or 20 turns) so are you turning it far enough. While adjusting the voltage por turn the current fully clockwise. If you have it turned down to minimum you will not get any volts.
Cheers Bob

5 Likes
5

Hi David,

Bob’s on the money with his suggestion.

If you disconnect the power (and perhaps have an extra set of hands you) should be able to measure the resistance between the legs of the pot on the bottom of the board using a multimeter and watch it change as you adjust the pot.

4 Likes
6

Ahh, Oliver, my bad. It appears I was too hasty and did not adjust the CV far enough. All good so far.

Cheers

David

5 Likes
7

No worries, glad to hear you’re back on track! Just let us know if you run into any more issues. :slight_smile:

4 Likes
8

Thanks.

4 Likes
9

Hi
I continue to get the output voltage the same as the input voltage even after adjusting the voltage by more than 30 turns in each direction. The green LED is on. This is the same for all of the 5 converters i have.
Do you have any suggestions?
Regards

1 Like
10

Hi Andrew
That looks suspiciously like something you are doing wrong. I can’t see 5 units having the same problem.
What voltage are you inputting. You will never get more than a bit less than that. The description says min input 4V.
Can you post a sketch of how you are connecting.

The 30 turns mentioned are 30 FULL (360Âş) turns. If your input is at the low end of the range any adjustment available will be right down near the bottom end of Pot travel.
Cheers Bob

1 Like
11

Hi Andrew, welcome to the forums!

If you could post some photos of your setup we may be able to give you some advice? Hopefully its some small overlooked mistake that is an easy fix.

Thanks!
Sam