LM2577S DC-DC Adjustable Step-up Power Supply Module

[Breaktru]

If you have a large enough box to house it in, check out these cheap step-ups:

Description:

    LM2577S non-isolated boost module
    Input Voltage: DC 3-34V
    Output Voltage: DC 4-35V (continuously adjustable)
    Input Current: 3A (max.)
    Output Current: 2.5A (max.)
    Operating Temperature: -40 deg C to +85 deg C
    Size (L x W x H): Approx. 1.2 x 0.8 x 0.6 inch / 3 x 2 x 1.5 cm

If you search around the cheapest I found it was......
$4.16 w/ free shipping.....
http://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l2736&_nkw=LM2577S

This is not my choice regulator for a mod but rather a cheap alternative.

[gknowes]

would be great if we could find that in 1.4mm x w

[perlionsmitnick]

What regulator would one use to make a 5 volt pass thru mod out of a 19 v laptop supply?

[CraigHB]

If you just want something small for 5V, this one would work.  It says 1.5A output current limit, but it can output 2A no problem.  I've used this regulator before.

You could also use an LM2596 based module.  You can find them on eBay for cheap here, but they're a lot bigger.

[Ian-C]

I have some of these boards and can't get them to work. I have them setup with 2 1400mAh 18500's in parallel and they work at the lower voltage but at 4.5 ish volts the board just cuts out, where i want them to do 3 volts to 6 volts.

I have measured the current draw and it seems to be about 1.5 ams at the point it cuts out so within the bounds of the boards. Any one got any ideas where I'm going wrong?

[Breaktru]

I have some of these boards and can't get them to work. I have them setup with 2 1400mAh 18500's in parallel and they work at the lower voltage but at 4.5 ish volts the board just cuts out, where i want them to do 3 volts to 6 volts.

I have measured the current draw and it seems to be about 1.5 ams at the point it cuts out so within the bounds of the boards. Any one got any ideas where I'm going wrong?

I read some posts and found that others complained about a large voltage drop with a load attached. Perhaps a High Drain battery may help.
Current in a boost module is higher on input than output. So... your battery has to be up to it or you will see a large voltage drop.
Spec's say 3 amp input max and 2.5 amp output max (if your battery can provide the needed amperage).
Standard Li-ion like the Trustfires max discharge rate is 1.5 amps while high drains max discharge rate can be 5.2 amps to 8 amps depending on type.

[CraigHB]

If the specs say 3 Amp input max, that's not much.  Neglecting voltage sag (due to battery impedance), it's 12 Watts with a fully charged cell, but drops down to 9 Watts when the battery has mostly discharged.  That can be exceeded at fairly low voltages depending on atomizer resistance.  For example, 4.5 Volts with a 2 ohm atomizer is 10 Watts on output.  Adding losses, that's approximately 12 Watts for input.  Also, that 3 Amps is probably a "best case" spec.  It's probably somewhat lower in practicality.

Boosters do have some surge currents on start up, but two parallel 18500s should be able to cover it without tripping the protection.  Internal impedance for a single protected cell is usually too high for a booster, but running two cells in parallel should drop it down low enough.

Boosters can not go below battery voltage less the voltage drop from the converter's rectifier.  If a booster uses a diode rectifier, it won't go below 3.7V with a fully charged cell.  If it uses a MOSFET rectifier which is more efficient, it won't go below 4.0V with with a fully charged cell.   To obtain a 3 to 6V range with a single cell, you need a buck-boost regulator.  Or you could do it the Chinese way with a booster then a PWM regulator (lame).

If you want a booster that can handle say a 2.5 Ohm atomizer at 6V, that's about 15 Watts output and 18 Watts input (but that varies depending on booster efficiency).  Using worst case state of charge for the cell, you need a booster that can handle 6 Amps input.

[bobbavet]

Gday Guys.

New to this forum. Thanks Breakthru. 

Looking to do some modding as my employment situ is erratic atm. looking to learn, kill sometime and maybe on sell a few mods.

Currently working with a couple of Vamo boards in SNUS Tins.

Ive been looking at these DC modules, I would like to know if any have an LCD that works with lower input of 4V. If not how do you ad an LCD? Also how can you externally operate the POT?

The answers are probably on here somewhere, so will keep browsing. If any mod vets has some quick links to posts would be appreciated.   

Cheers Bob

[charming]

Gday Guys.

New to this forum. Thanks Breakthru. 

Looking to do some modding as my employment situ is erratic atm. looking to learn, kill sometime and maybe on sell a few mods.

Currently working with a couple of Vamo boards in SNUS Tins.

Ive been looking at these DC modules, I would like to know if any have an LCD that works with lower input of 4V. If not how do you ad an LCD? Also how can you externally operate the POT?

The answers are probably on here somewhere, so will keep browsing. If any mod vets has some quick links to posts would be appreciated.   

Cheers Bob

Welcome bob! 

I think the on board trimmer pot is 10K ohms. If you unsolder or disconnect it, you can use a different style 10K and mount it on the case for easy access.

LCD? or LED? Display

[CraigHB]

Ive been looking at these DC modules, I would like to know if any have an LCD that works with lower input of 4V. If not how do you ad an LCD? Also how can you externally operate the POT?

Hi Bob,

Unfortunately, generic off-the-shelf booster modules are pretty hard to find that can support the outputs we need to power an atomizer.  There's really only one that's been found to work well (the TI module).  High power modules with both buck and boost to support outputs above and below battery voltage are non existant.  The controller chips needed to build these types of regulators abound, but you need to be an electrical engineer to design and build a whole regulator with one. 

The only option for a display is to use a controller board designed for an e-cig.  There's the DNA20 and another one out there (can't remember the name) that also has a display.  You can use one of the Chinese boards like the ones for a Vamo or Zmax if you can find one.  Usually, it's not much more expensive just to buy the whole device and scavenge the board from it.  There's a difference with those Chinese boards.  They use a PWM output instead of using a purely DC output.  Some say it's better to have a DC output, some say it doesn't matter.

[bobbavet]

Thanks Charming. So you just wire those display in circuit?

Thanks Craig. I don't understand, I see these boards in mods all the time. or are they something different.

[Breaktru]

Thanks Charming. So you just wire those display in circuit?

Thanks Craig. I don't understand, I see these boards in mods all the time. or are they something different.

The display is an LED. Just wire it across the output to read output voltage. You can also use a slide switch and wire it to read Input and Output voltage.

For an LCD display you would need to design and built the circuitry to use an LCD display or go with the DNA20 or Vamo board that has an LCD built in.
The LM2577 is a low powered board. I personally do not use it because of that. If you use high wattage, this is not the board to use. The reason people use this board is because it is cheap and easy to wire.