Is this misleading, or not?

I bought some of these from eBay:

http://www.ebay.com.au/itm/1PC-New-1A-3V-to-5V-DC-DC-Converter-Step-Up-Boost-Module-/380655215690?

1PC New 1A 3V to 5V DC-DC Converter Step Up Boost Module

Description includes:

Input voltage: 2.5V-6V
Output voltage: 4V-12V (adjustable)
Output Current: 1000mA (Max)
Conversion efficiency: 92% (the highest)

It's the Output voltage (adjustable) I'm having issues with. The item looks exactly like in the photos on the page. However I don't see how you adjust the output voltage.

A couple of queries with the vendor later and I get this:

the output voltage is adjustable by change the acquiescence voltage
you can follow the below formula :
output voltage =(R1/R2+1)*0.6v
The acquiescence voltage of R1 is 8.2K , R2 is 1K
first ,you have to cancel one of the voltage R1 or R2
then follow the formula to add and change the new voltage you want

Now R1 and R2 are not marked on the board, and after a further message he sent a reply showing which ones they are. He also was unable to supply the schematic or any more information.

Would you say "adjustable" means "easily adjustable" (like, you turn a trim pot)?

Surely desoldering one or two tiny SMD resistors with a reflow workstation, buying replacements, and soldering them in, after following a vague formula without any schematic, is not really "adjustable"?

You may solder ie. a 10k trim pot there (instead of R1,2) and it becomes adjustable - those modules are standard dc-dc converters where the output voltage is set by the divider connected to output (most probably)..
PS: you may solder the trim pot without desoldering the resistors, provided the resistors there are of higher value..

Yes, but if I buy something advertised as "with wheels" and I have to install the wheels myself, isn't that misleading?

I would say the "adjustable" is not "too much" misleading in this case as there are dc-dc chips with a specific output voltage without such an adjustment option.. :slight_smile: And for Au$1.05 you can hardly get wheels mounted :slight_smile:
Moreover, the ad says: "1A 3V to 5V DC-DC Converter"

The title on Ebay is correct, it is a 3V to 5V step-up converter.

By altering the hardware, the output voltage can be changed.
I think the word "adjustable" is misleading.

However, it can be a bad translation. English is also not my native language, and I don't have a big problem with "adjustable". It is very cheap, perhaps too cheap for a potentiometer. You can see for yourself in the photo that there is no potentiometer.

My conclusion: It is misleading, buy you should (could) have know better. XD

(while I was typing this, pito wrote the same).

ADDED: This one seems to be the same, and there is a schematic on that page and explanation how to change the output: http://www.ebay.com/itm/DC-DC-Power-Supply-Converter-Step-Up-Boost-Module-1A-3V-to-5V-/370883602130
Problem Solved.

OK, I'd forgotten about the language issue. All is forgiven. :slight_smile:

And I admit that it is damn cheap.

As I can see the pcb it seems to me the 3 pads (near the larger [] pads for output marked Out+ Out-) are actually dedicated for the trim pot..

Picture deleted

By that definition, anything you buy could be defined as 'adjustable'.

"This child's bicycle is adjustable to a top speed of 150MPH**"

** By completely replacing the frame, engine, wheels and more or less everything else.

As you note, removing and replacing 0402 resistors doesn't seem like a reasonable definition of 'adjustable'. I've a full reflow setup at home and I wouldn't be too keen to try it.

I can't see the item because of that :

Unfortunately, access to this particular item has been blocked due to legal restrictions in some countries. We are blocking your viewing in an effort to prevent restricted items from being displayed. Regrettably, in some cases, we may prevent users from accessing items that are not within the scope of said restrictions because of limitations of existing technology. Please accept our apologies for any inconvenience this may cause, and we hope you may find other items of interest on eBay.

but I agree with Nick, "adjustable" is misleading here. You should be able to adjust without having to change any component. And no, "being cheap" is not a universal excuse . They should have written something like "output voltage = formula (can be modified by changing R1 value)"

I do not think the "adjustable" is misleading in this case:

  1. legal - the word "adjustable" is used in the detailed technical description as "(adjustable)" in brackets - it means "an option", what is generally accepted form used even in datasheets of a very big vendors..
  2. the ad says it is a "3 to 5V dc-dc converter"
    3. there are pads for the external trim pot (see above picture), most probably..
  3. a customer shall consider the price when doing a purchase - that could be an indication his requirements may not be fulfilled fully..

Perhaps my 'ADDED' section in reply #4 got lost. I didn't expect so many posts.

I think you're right about the external trim, and I'd agree with you if they gave a schematic, but here, you have to guess .

Erdin:
Perhaps my 'ADDED' section in reply #4 got lost. I didn't expect so many posts.

ok, just seen it right now 8)

You may see a 20% higher price provides you with the schematics as well.. :slight_smile:

I see what you mean about those extra holes. Interesting. However they declined to give me a schematic, or tell me what the main chip's part number was.

I must admit it is a bargain at $1, and assuming you want 5V output (which I probably would) is ideal for that situation.

There's an LED that lights up under certain circumstances, I don't dare ask what that is supposed to indicate.

Nick - there is the schematics in Erdin's replay above..

Ah I see, I must have missed that "added" bit. Thanks very much.

The four holes make sense now. Next time I'll pay 30c more for a more detailed explanation. :slight_smile:

The offer including schematics in ErdIn's post is wrong at least regarding the naming of the resistors in the schematic,
compared to the formula Vout = (R1 + R2) / R2 * 0.6
should rather say R3 and R6 ??? ( 8.2k + 1k ) / 1k * 0.6 ~ 5.5 ???

Worst thing is that you obviously do not get a USB connector with neither the AU$ 1.05+0.49 nor the US$ 1.30+Free shipping (@currently 3bids) item.

BTW: That's what the 4 holes are meant for, see this
This connector at least doubles the value and still provides an "adjustable" boost converter :wink:

I don't think the term misleading is appropriate to classify one offer vs. the other.

I believe it is misleading.
If we wish to be generous, we can say that it is a language difference.
I do not believe that it is adjustable, it could better be described as alterable.
You can adjust the volume, the brightness or the contrast.
You can alter trousers, dresses or hair color.

Sorry but "adjustable" means you turn something with a screwdriver or perform a similar simple action. Saying you can replace components to get a different output does not make the device adjustable any more than saying the clock speed on an Arduino is adjustable because you can solder a different crystal in place or saying that an LED torch brightness is adjustable because you can change the LEDs.

I would give them the benefit of the doubt and say it's a language issue, but the cynical old fart in me thinks they are stretching the truth envelope.


Rob