Un-expected Voltage under load

[proax9]

On a breadboard-
I am using a TI PTN04050c booster- with a 14500 AW IMR battery (fully charged ~4.2v)
I am testing different resistors between pin 3 and 4, to try and get approx 4.1-4.2 regulated voltage.

I am testing voltage:
under load (the same 2.5 ohm Boge carto on all tests) AND
no load- reading off leads from where carto would be hooked up.

I do not understand the results: (all resistors have been metered to be accurate, as well as the carto)

Res 86.6k no load 4.51 v Under load 3.95 v
Res 47k no load 4.31 v Under load 4.12 v
Res 33k no load 4.06 v Under load 4.13 v
Res 22k no load 3.83 v Under load 3.87 v

The no load voltages are pretty much what I expected- higher voltage with higher resistor.
but the under load seem like they are (for the most part) increasing at at lower resistance.

??? HELP ???

 

[slimest]

proax9, looks like voltage drop in the wiring or battery. Try INPUT voltage on the booster board first. If you see significant input voltage drop under load, try input voltage on the battery. If voltage drops only on the board input contacts, you have to consider better wiring between battery and the board. Breadboards frequently cause voltage drops because of their thin wires and bad contact. Switches also could be guilty. If voltage drops also on battery, you have to use another one, more powerful.
If no voltage drop on the input, check out output wiring between board and atomizer. The same method: measure on the booster board and on the atomizer.

 

[WillyB]

On a breadboard-
I am using a TI PTN04050c booster- with a 14500 AW IMR battery (fully charged ~4.2v)
I am testing different resistors between pin 3 and 4, to try and get approx 4.1-4.2 regulated voltage.

Well I don't think that is the correct way to go about it, 4.1-4.2V is too low.

The TI PTN04050c is a booster.

A boost converter (step-up converter) is a DC-to-DC power converter with an output voltage greater than its input voltage

Step-Up (Boost)

• Low peak current
• Low-side switch
• Simple inductor
• Low switch-stress voltage
• VOUT must be greater than VIN
• Output cannot be completely turned off

To make sure the assembly is working correctly, are you getting ~5V unloaded 'naked' (no resistors added)? Then again, this time with your 2.5Ω load? In your example your first and last figures look like straight battery voltage.

Best to first make sure it's working properly, you might also try a larger battery for input. If it works as I suggested, naked, the easiest solution would probably be to forget resistors and just use a diode on the output.

From Ralph T:

Diodes drop a fixed amount of voltage when forward biased (current flows). The amount depends upon the type of diode, ranging from .5 to .9 volts generally. I bought some diodes rated for 3 amps from Radio Shack and determined that they drop .82 volts each

He was talking about the 3A barrel diodes from RS.

5V - .82 = 4.18V. Done

 

[StrikeEagleCC]

Since the 04050 isn't *intended* for operation below 5 volts, I imagine that it's behavior may get unpredictable at lower values. I know breaktru has done a lot with that converter, you may want to check out his threads if you haven't already. The fact that you're getting large voltage drops with some resistor values, and small drops with other values makes me think that the drop isn't likely to be in the wires or connections--I would expect to see similar drops proportional to the output for each resistor, but like slimest said, test everything. Let us know what you figure out!

 

[asdaq]

Something is certainly wrong in the setup. Jhonutz put a 100k pot between 3 & 4 and gets 4.3-4.8v which pretty much covers the range you are trying with fixed resistors. The readings you are getting have huge drops and I'd suspect it is starved for current possibly with the ground connection. Perhaps the breadboard connections are to blame? If the circuit is complete but the 4050's ground is disconnected (but not the atty) it will pass battery voltage to the atomizer.

 

[WillyB]

Jhonutz put a 100k pot between 3 & 4 and gets 4.3-4.8v

Why Jhonutz? This undocumented way to change the the output voltage was first noted years ago by Nuck with his Fistpack work.

Alternate Lower Voltage Build

For those that want the slider to output between 4.0 and 4.5v there is a really easy trick that RjG shared with me. If you add a 100k resistor between the Adj pin and and vOut pin on the booster the 4 voltages will be changed...

The best part is, the booster is only generating 4.6v so it also adds some battery life to each cycle.

Thanks again to RjG again for sharing.

His guide is essential reading for PTN04050c booster users.

https://docs.google.com/Doc?docid=0AXdaMZo4FKMVZGhqdnE4YnNfNDNjN2Q0cHBoZg&hl=en&pli=1


asdaq, you're a fixed voltage TI booster user, what value are you using and what voltage did you get?

 

[Robert T]

Willy, with a 82K I got 4.6v.

 

[asdaq]

Sure, Nuck did resistors on a slide switch, but jhonutz put a 100k pot on there, which gives a full range of ~0-100K resistance. The pot idea I like but haven't had the room for one lately. If someone were to add a pot and take resistance measurements from the legs for a list of voltages, that would be great to know.

So far I've built with these combinations:

5.0v - OPEN
4.6v - 100k
4.57v - 82k
4.43v - 62k

Loaded voltages within a hundredth of a volt of these.

The last 5 builds or so have been with the 62k, a favorite of sorts.

 

[proax9]

So far I've built with these combinations:

5.0v - OPEN
4.6v - 100k
4.57v - 82k
4.43v - 62k

Loaded voltages within a hundredth of a volt of these.

The last 5 builds or so have been with the 62k, a favorite of sorts.

What battery are you using?

I am beginning to suspect I have some poor connections- as one of my units performs better than another with same carto and batt.

THX for everyone's thoughts / ideas.

(back to testing...!)

 

[WillyB]

but jhonutz put a 100k pot on there, which gives a full range of ~0-100K resistance.

You are talking about Adj to Vout? Nuck's resistors are used in the documented Rset mode, Adj to GND.

And what kind of range could you get with ~0-100k from Adj to Vout? High of about ~4.6V and on the low end does it just bypass the booster and use battery voltage?

 

[asdaq]

Proax, they are IMR's and CGR's all high drain, and good connections are important indeed.

Willy, yes, Adj to v-out. I thought Nuck had these too but it has been awhile since I looked at the fistpack. He does have the 3A diode also, as Adj to GND only sets it to higher than 5v so that makes sense to get something below 5v.

I don't know about the second part, jhon said 4.3-4.8, but my 100k gave me 4.6v. Perhaps he had a resistor in line too and i don't remember this. This Adj to v-out certainly doesn't seem to be a linear relationship and I suspect below a certain threshold this doesn't have an effect and the booster is engaged and supplies a certain minimum v-out>v-in. Only when it is not engaged does it pass battery voltage.

The starved for current situation when it whines probably delivers somewhere around 3.5v but that isn't working properly at all.

edit: Gah! I did this back in January and the same mistake again! It wasn't jhonutz but bohoo, my apologies to both.

Anyway to quote bohoo:

the pot is 100k, capacitors 100uf, and i left out all resistors. The pot is between pins 3 and 4. I get 3.3-4.7 V this way which is enough for me. Under load using 2.0 ohm atty it drops only about 0.2 V.

From this thread: http://www.e-cigarette-forum.com/forum/battery-mods/258248-ptn04050-booster-need-help-since-i-succed-ptr08100-next.html

And proax, maybe check the ground connection again, that fixed it last time .