Terminal connections for a Voltage Regulator

[37lover]

I have purchased some cheap step down DC voltage regulators to use with my layout lighting, but embarassingly I am struggling to understand how to correctly connect them.

I may use a 16VAC [first through a bridge rectifier] or even 12VDC supply. But I am confused by the numerous terminals on the regulator. The reg does have an adjustable output as well as 4 set outputs - 3.3, 5.0, 9.0, and 12V.

On the rear of the board there are four terminal on the short side VO+, GND, IN+, and EN. Across the long top edge there are five terminals 3.3V, 5.0V, 9,0V, 12V, and ADJ.

Rightly or wrongly I would assume the positive input is connected to the left end IN+ and negative to the GND terminals. And if I want 9.0V then take the positive connection from the 9.0V terminal and return also to the GND. So what is the EN terminal for? And what is the VO+ at the top of the left side for?

This first photo is the front of the regulator

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This second photo shows the terminals on the rear side; this is vertically flipped relative to the first photo.

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[Rog RJ]

 

To save anyone from searching, the details are here but they're a bit sketchy  https://www.alibaba.com/product-detail/DC-DC-converter-12V-24V-to_62092735266.html?spm=a2700.pc_countrysearch.main07.52.41ae6ddeaAKUhK

 

[ColinB]

Not being an expert on this board, I am assuming it came from China, as they never come with instructions. My best guess as Clarkson puts it, is :-

 

VO  - Voltage output

GND  - O volts

IN+ - Unregulated input voltage

EN - a signal line to switch it on or off.(stands for Enable)

ADJ - adjustable voltage input, i suspect but the regulator is fixed.

 

What might be a good idea is to read the number of the 8 pin IC and Google it to see the applications.

Also the circuit board may be a multiple purpose one, so depedant on what components are on the board determines what outputs are in use.

What is the best idea if you have multimeter, is to power it up with a votage between IN+ and GND and see what you get. You might need to connect GND an EN to get it to work, but try it first without.

[EnGee]

I would agree that EN is probably 'enable' but would suggest that ADJ is probably an adjustable OUTPUT (not input).

As stated, power it up and see what happens.

[ColinB]

Yes, I agree ADJ sounds more like an adjustable output, which might be what the potentiometer is for (that is what it looks like). I checked that site but it wasn't that much more informative.

[37lover]

Thanks for comments so far.

 

Yes, the board does feature an adjustable setting.

 

I did manage to get a response from the Seller [yes in China] and understandably the written english is not perfectly clear [however much better than my Chinese would be].

 

The EN terminal is not used

 

Input is connected to IN+ and GND.

 

The default set up goes through the adjustable regulator and is connected via VO+ and the GND terminals on the left side. If I want to use one of the set voltages I have to solder a short between the large and small adjacent blocks on the rear BUT I also have to break a connection somewhere to isolate the adjustment feature. Unfortunately the picture the Seller sent me missed the location of this break.

 

The connection for the set voltage(s) is still taken from the VO+ and GND terminals and not as I initially thought from the large & small pairs of terminals across the top long edge.

 

Getting there.

[AndyMac1707817969]

Been about 25 years since I built a stable DC PSU using straightforward regulators such as a 7805 and 7812. Things may have changed since then but they always required a heatsink. I assume the component marked 4R7 is the regulator so may require one attached to it before you power this up.

[Chrissaf]

The technical blurb for this product such as it is, states that no 'heat sink' is required up to 2 Amp current draw. One is required however if you want to push the load to the max 3 Amp.

[EnGee]

I would be very careful about breaking any connections, doesn't sound right to me. What happens when you put power on it and meter the outputs?

[37lover]

Correct; 3A is the maximum, 2.1A is the recommended nominal working.

[EnGee]

So looks like I might have been a bit over cautious in saying 'be careful what you cut!'. This ebay listing shows exactly what all the connections are and where to cut. 

 

https://www.ebay.co.uk/itm/DC-Buck-Step-down-Adjustable-Voltage-Regulator-Module-5v-24v-to-1-8v-3-3v-12v-2A/254604769344?hash=item3b47a07840:g:Rq4AAOSw6n5Xqd5A

 

(Don't think the link is clickable so you might have to copy and paste it into your browser.) or search

eBay item number:254604769344   Or alternatively just use it how it is and adjust the output voltage to what you want - simples!

[Chrissaf]

Good find EnGee

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Your link clickable

.

Copy below should the link expire some time in the future.

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[37lover]

Gents,

Yes, I too had subsequently managed to find the item [although not the one I purchased] and instructions linked by EnGee and shown above by Chrissaf. If you look at my photo of the rear of my item it does have the link to be cut in Step 1, or at least not to my eyes.

[Chrissaf]

So I see.

.

Your orange one says version 1.0. So I assume the green one is a later version. This green one also has more fixed voltage preset options as well [two more below 3.3 volts]. However the main connection pads for the variable voltage appear to be the same and, of course, you can always just adjust the voltage you want rather than cutting tracks for a fixed option. You also said that the seller gave an unclear indication where the track needs to be cut. Although unclear, is there any indication that it is in the vicinity of the green cut track location.

[96RAF]

If you trace the pcb tracks it looks like the cut on the red board may be on the other side where there is a 1 just to the right of the trim pot.

All you are doing is removing the default voltage short at the end of that row of broad/narrow jumpers then solder linking the jumper for the voltage you want to use.

Working on that premise you can cut the short wherever is easiest to get at.. If you do it wrong then just resolder the gap you made.

[37lover]

Thanks again,

The Seller sent me a picture and explained that I had to cut where shown by the "blue circle", but there was no blue circle. I have asked him/her to resend the picture and hope to receive this by tomorrow morning. I have a few other things to be getting on with so can wait a bit longer. I probably will use the adjustable option to fine tune the output voltage but out of curiosity would like to see the "correct" method. 

[37lover]

No new picture yet. But a question for the electronic experts.

 

if I use the adjustable option I can obviously set the output voltage to "exactly" what I need to light up a string of led's [in this instance only 2 x SMD 5630's], so I presume it is better to do this and not include a nominal resistor in series. Unless there is some other benefit / safeguard by incorporating a resistor?

[Chrissaf]

I have written at length before on the forum a detailed explanation of why a resistor should always be included. Even if it is only 10 ohms. Yes you can get away without one if you have 100% control over the voltage, but why risk it.

[37lover]

Chrissaf,

It is probably a snippet from one of those lengthy articles that has lodged in my brain and made me ask the question, thanks I shall incorporate a 50 ohm resistor.