LDO Voltage Regulator - Anybody Interested

[Laredo7mm]

I have been seeing quite a few posts about which is better, a resistor or diode, for dropping the voltage of a multiple battery mod. Neither are ideal. Both will still allow your output voltage to decrease as the batteries drain and the resistor wastes battery power.

The best way to go is with a low drop out (LDO) voltage regulator. A LDO will keep your output voltage constant as long as your input voltage is above a certain threshold. The problem is that either the LDO is too big to fit in the mod, or too small/complicated for most people to deal with.

I was checking out some parts and I think I can make a voltage regulator assembly that will put out 2 amps at 5V (or 4.75, or 4.5, etc.) and handle the voltage from any two cell li-ion or li-poly battery pack. From my initial findings, I think I could package that into something about 12mm by 12mm square. An adjustable regulator is possible, but that would be bigger. Those variable resistor are big.

If there is interest, I will design something up and put together a price.

Let me know.

 

[Kewtsquirrel]

I'm interested if the price is right, I've actually got a supplier for 5v buck/boost regs but they can only handle 700mA at 3.7v and are about $10 per my cost.

Let me know how much you can put yours together for, I might buy a handful.

 

[HockerMagnum]

Could you design a constant (or adjustable) current circuit for a 7.2 volt 1200mah ni-cad battery pack?

Wouldn't have to be micro size. I would just plug it in between the battery pack an my home made manual 801 pipe.

HockerMag

 

[mogur]

I posted this a few days ago-

the datasheet-
http://www.national.com/ds/LM/LM2940.pdf

and here's the part at digikey for $2.15-
Digi-Key - LM2940IMP-5.0CT-ND (National Semiconductor - LM2940IMP-5.0/NOPB)

Stick with the sot-223 chip at 7mm square versus the TO-220.

It is a .5 v drop regulator in the standard output values (4, 5, 6), handles 1 amp, but is way smaller than the usual TO-220. Could probably find the chip for a buck at surplus houses. You need an under voltage cutout to avoid over-discharging the li-ion cells, however.

 

[Walrus]

I picked up that TI chip. Just seems my eyesight and my shaking hands are keeping me from doing any soldering with it. I'd pay to have one soldered and ready to go for me

 

[kinabaloo]

For the regulator to work well with a 6v battery the best output voltage to go for is 4v.

A 5v regulator will work but degrade the performance as the battery fades; from 6v to 4v will have much less degradation.

4v is also more suitable for most atomizers.

Wasted power could be as high as 10% in some situations (with diodes it is virtually zero).

Starting out with 5v and wanting 4v? Use series connected power diodes (1N4001).
Starting out with 6v or more and wanting 4v? Use a voltage regulator (low dropout, 1A)

 

[kwcharlie]

The LM's are good. Also the 79m05 is OK, two in parallel will give 1 amp and if you have an old 'box of chips' more likely to have.

 

[Laredo7mm]

...Stick with the sot-223 chip at 7mm square versus the TO-220.

It is a .5 v drop regulator in the standard output values (4, 5, 6), handles 1 amp, but is way smaller than the usual TO-220...

Yes, and to my point, the typical modder is not going to have the abilty to solder a SOT-223. Off the top of my head, I think the pins are 0.35mm wide and on .95mm centers. The SOT chips are very small and hard to use if you don't have the correct equipment.

 

[Laredo7mm]

Here is a picture of a SOT sized chip sitting on top of a US Dime.

 

[Laredo7mm]

The LM's are good. Also the 79m05 is OK, two in parallel will give 1 amp and if you have an old 'box of chips' more likely to have.

Yeah, maybe if you want a 1.1V drop out and try to fit two T220 or two DDPAK sized chips into your mod.

 

[Laredo7mm]

This is not ment to be mean, but this thread is not for discussing which voltage regulators to use. I can figure that out.

I was looking for feedback on if any of the modders out there would be interested in a pre-made voltage regulator that they could use in their mods.

So, please, keep your chip suggestions to yourself, or go start your own thread.

Thanks.

 

[Laredo7mm]

For the regulator to work well with a 6v battery the best output voltage to go for is 4v.

A 5v regulator will work but degrade the performance as the battery fades; from 6v to 4v will have much less degradation.

4v is also more suitable for most atomizers.

Wasted power could be as high as 10% in some situations (with diodes it is virtually zero).

Starting out with 5v and wanting 4v? Use series connected power diodes (1N4001).
Starting out with 6v or more and wanting 4v? Use a voltage regulator (low dropout, 1A)

Good info kinabaloo, that is one big advantage to using a variable resistor in the design to set the output voltage. The variable resistors I have seen are just so dang big. The smallest I have found are about 4mm x 4mm.

I guess I should just design the board and see what it looks like with a trim pot in there.

 

[Walrus]

Here is a picture of a SOT sized chip sitting on top of a US Dime.

Damn, I wouldn't even be able to see the chip, much less the leads.

 

[Laredo7mm]

Damn, I wouldn't even be able to see the chip, much less the leads.

LOL, yes they are small. Not too bad when you are putting them on a printed circuit board (PCB), but they are still small.

That chip is a supervisory chip that I tried to use as a low voltage warning to turn on an LED when the voltage dropped below 3V.