WTH am I doing wrong... LM2596 VV Box not VV-ing

[Wulfie]

Ok... been waiting 3 weeks for my ebay order for some LM2596 boards to show up... they FINALLY did today (!). I pulled one off the strip and did a test hook up for a box that has been impatiently sitting on the shelf waiting for it. Two Ultrafire 14500's, madvapes horn switch, LM2596 board, atty connection... mad vapes digi volt display hooked to the atty connection. Turn the switch to on, press the horn button, display says 7.3. Turn the brass screw... no change... keep turning the screw... still no change... turn the screw back the other way... no change... WTH??? Unhooked everything, wire in another LM2596 board... same voltage display (7.3)... turn the screw again... no change again... search the boards... no help... Anybody have an idea on what I'm doing wrong?

This is the board that I got off ebay... http://www.ebay.com/itm/260858526297

 

[Eliteedge_7]

how do you have it wired. diagram... picture please, makes it easier to figure out what might be the problem.

 

[jhonutz]

where write In+ you in with voltage from that two battery series connected. On Out put voltmeter .

between IC and trimer you have a SMD resistor, it`s ok or is broken?
From your descriptions most likely not work feedback divider and have two resistor a SMD and trimmer.Check out the layout from IC pin4 to middle of resistor divider.

 

[TomCatt]

Just curious as to what you mean when you said you pulled one off the strip? The ones I've received have either been individually packaged in anti static bags or at least individually wrapped in bubble wrap.

Since there is no need to breadboard these, I have a 2 AA box that I put alligator clips on the leads. Put 14500s in the box, clip leads to IN pads, clip multimeter leads to output pads to check them out.

 

[Wulfie]

Didn't think my wiring description lacked mental imagery... But ok... Wired up the board like Mamu did http://uwww.howder.com/lm2596.jpg.

Did not breadboard, but wired up to test/play before mounting in box.

I ordered 5 boards, they came as a strip (long board pice across the top, scored fir the end of each vv board, presumably for a production/assembly where the worker/machine would pop one board off the strip)

Jhonutz... No offence, but that was waaaaay too technical for me (is why I bought a prebuilt board and not parts to assemble)

 

[Eddie.Willers]

The only thing I could figure - looking at the Ebay pic - is that the type of potentiometer they are using is one that needs 15+ turns for the full range of adjustment. Is it possible to turn the screw more than a complete revolution? Have you tried it? What happened?

But, you say the voltage on the meter is 7.3 - too close to the input voltage to make me confident that you have correctly working boards.

 

[Dougiestyle]

Those pots take a significant amount of turning to adjust voltage. Like Eddie says, tho, with both putting out close to the stacked batt voltage, you may have DOAs.

 

[notsmoking]

Where is it you had the meter for checking voltage.... it does not show that in the pic

 

[Wulfie]

Turned it over 30 revolutions... No resistance, no stop, no odd noises. Voltage straight off the batteries is 7.9, so there is something happening, just no adjustment.

I can see one DOA in 5.. two tells me it is something I'm doing wrong or just missing.

Wanted to try to replace the pot on one with a thumb dial style... Might have to try that sooner than expected to see if it really is a bad pot. Dunno.

 

[notsmoking]

You should be checking the voltage at the atty or at the voltage out on the board

 

[TomCatt]

I'm sure you did; but I gotta ask anyway...did you turn the pot both ways? I was testing one of my LM2596s this morning and kept turning the pot screw what I thought was decreasing voltage. No change, 7.4V; thought 'Uh oh', then turned the other way and got adjustment

 

[Barryg41]

I'm sure you did; but I gotta ask anyway...did you turn the pot both ways? I was testing one of my LM2596s this morning and kept turning the pot screw what I thought was decreasing voltage. No change, 7.4V; thought 'Uh oh', then turned the other way and got adjustment

I just did the same thing. Clock wise for volts up negative side of regulator pointing to me. Went up pass max input volts over ten turns. It took the same turns to get it back down to adjusting volts again. So if your 30 over you might have to turn it down 30 to get it to adjust again.

 

[Barryg41]

I'm sure you did; but I gotta ask anyway...did you turn the pot both ways? I was testing one of my LM2596s this morning and kept turning the pot screw what I thought was decreasing voltage. No change, 7.4V; thought 'Uh oh', then turned the other way and got adjustment

I just did the same thing. With the regulators negative side to me. I turned until it stopped at input volts, I kept turning for 10 turns. Then went back 10 turns and it started again to reduce output voltage. Clockwise for increase in volts. I would turn ccw till to reads.

 

[Barryg41]

Sorry for double post? Well it wasn't a double post. The first one would not send. So I tried again the second time!?!?

 

[Wulfie]

As stated in OP, voltage on the mad vapes voltage display screwed into the atty connection (wired to the "out" of the board) read (and stayed at) 7.3v, voltage from the batts read 7.9v.

And yes, cranked it in both directions... Ugh. Guess I'll keep cranking it ccw until it either drops or pops.

Thanks all.

 

[jhonutz]

the answer is in my early post, if you wired correctly same to have a bad soldering or a broken component, of course if the seller was made that PCB according to the schematic

 

[retird]

If you could post a picture of your completed unit so all can see the wiring....it would be helpful in helping you out....kinda hard to hit a blind target....

 

[iamtopher34]

Push and hold the fire button and give it a few turns down and recheck

 

[Ms. Creant]

Just a thought, but the output cap will still have the full voltage for a while if there was no load. Put an attie on and measure the voltage at the output of the board while powering the atty and turning the VR.

 

[WillyB]

Well how about this for a thought.

It's $2.18, shipping included. I just checked, HK Airmail would be about $1.68. So basically you bought a 50¢ assembly. I imagine the seller is making a profit, so what did it cost him? 25¢?

Food for thought.