5v regulator

[h8isgr8]

Lets take this example:

A 9VAC @ 1300 mA wall wart, adding an inline UCC383TDKTTT-5G3 regulator.




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First, is it a switching supply or a linear supply? You can usually tell by the weight of it alone.

Second, "9VAC" means that well, it's AC. You can't feed AC to a regulator, so you would need to rectify and filter it.

It's impractical to add a linear regulator to a switching supply because the main purpose of a switching supply is it's efficiency. Linear regulators are extremely inefficient and "waste" the extra power as heat.

 

[warp1900]

First, is it a switching supply or a linear supply? You can usually tell by the weight of it alone.

Second, "9VAC" means that well, it's AC. You can't feed AC to a regulator, so you would need to rectify and filter it.

It's impractical to add a linear regulator to a switching supply because the main purpose of a switching supply is it's efficiency. Linear regulators are extremely inefficient and "waste" the extra power as heat.

So according to what you are telling me, using the same regulator but with power from batteries, it would also be inefficient?, or are the results different?


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[h8isgr8]

So according to what you are telling me, using the same regulator but with power from batteries, it would also be inefficient

Technically, yes.

Since the linear regulators you have were free samples from TI, you should have added these efficient switching regulators to your cart.

http://focus.ti.com/docs/prod/folders/print/pth08000w.html
http://focus.ti.com/docs/prod/folders/print/pth08080w.html

 

[warp1900]

Technically, yes.

Since the linear regulators you have were free samples from TI, you should have added these efficient switching regulators to your cart.

Plug-in Power Modules - Non-Isolated POL - PTH08000W - TI.com
Plug-in Power Modules - Non-Isolated POL - PTH08080W - TI.com

I don't doubt you know what you are talking about, but honestly, I have been happily vaping for days with the 5v regulator running on 2 x 14500 batteries with amazing performance.
Also, while I was sitting here reading the forum and your responses, I added a regulator to my 9v power supply and it works the same.

So, while theory might say it is "inefficient", once again, reality has the last word.

Maybe I would get a tiny bit more "juice" off my batteries doing this or that, but I really don't need to complicate things any further, this really works.

 

[Nuck]

Technically, yes.

Since the linear regulators you have were free samples from TI, you should have added these efficient switching regulators to your cart.

Plug-in Power Modules - Non-Isolated POL - PTH08000W - TI.com
Plug-in Power Modules - Non-Isolated POL - PTH08080W - TI.com

You have a knack for finding some extremely useful chips. Ive been using LiFEPO4 bats on my higher voltage mods so the voltage lost at full with a linear regulator is only 1.6v but its still a huge waste. Using li-ion bats the waste goes up to 3.4v which is quite a bit of overkill. I've been looking for a good switching regulator that would do the job with high efficiency.

I think its a safe bet that these will work without the caps.

 

[h8isgr8]

I don't doubt you know what you are talking about, but honestly, I have been happily vaping for days with the 5v regulator running on 2 x 14500 batteries with amazing performance.
Also, while I was sitting here reading the forum and your responses, I added a regulator to my 9v power supply and it works the same.

So, while theory might say it is "inefficient", once again, reality has the last word.

Maybe I would get a tiny bit more "juice" off my batteries doing this or that, but I really don't need to complicate things any further, this really works.

My point was, from a technical perspective, it's just plain wrong to use a linear regulator to drop the voltage from a switching power supply.

 

[warp1900]

My point was, from a technical perspective, it's just plain wrong to use a linear regulator to drop the voltage from a switching power supply.

Point taken, that is something I can understand right away, I am going to order the ones you suggested.

Thank you h8.

 

[mnealtx]

Nice find on the power modules, h8!

It looks like this may be better for our applications, due to a higher max I(out).

 

[h8isgr8]

It looks like this may be better for our applications, due to a higher max I(out).

Yup, that one will work too. It might be a bit easier to wire up as well.

 

[mnealtx]

To be honest, I was looking at the Imax - I could conceivably pop that thing running it at 5v if I put one of my lower resistance 510s on there.

 

[h8isgr8]

To be honest, I was looking at the Imax - I could conceivably pop that thing running it at 5v if I put one of my lower resistance 510s on there.

I highly doubt it, unless the resistance is <0.8R.

There is this one if you're still paranoid....

Plug-in Power Modules - Non-Isolated POL - PTR08100W - TI.com

Have a 0.3R atty?....

http://focus.ti.com/docs/prod/folders/print/pth08t221w.html

 

[mnealtx]

I highly doubt it, unless the resistance is <0.8R.

Nope, all of my 510s run between 2 and 2.2 ohms. Unless they changed Ohm's law on me, that means that my 2 ohm atomizer being fed by 5 volts equals 2.5 amps, which is more than the Imax of the chip. The 2.2 ohm attys would pull 2.27 amps. I don't care to push devices that close to max, or over max.

 

[h8isgr8]

Nope, all of my 510s run between 2 and 2.2 ohms. Unless they changed Ohm's law on me, that means that my 2 ohm atomizer being fed by 5 volts equals 2.5 amps, which is more than the Imax of the chip. The 2.2 ohm attys would pull 2.27 amps. I don't care to push devices that close to max, or over max.

I thought you were talking about the PTR08060W.

Anyway, I don't think a 2R atty would even be an issue for the PTH08000W in this situation. The max rating is more of thermal limit based on continuous use. It has over-current protection anyway, so it won't "pop", it will just shut down.

No point using it in your case though since there are higher current models available for the same low price of free.

 

[mnealtx]

I thought you were talking about the PTR08060W.

I'm sorry that I wasn't clear on which one I was talking about - I figured it was apparent.

Anyway, I don't think a 2R atty would even be an issue for the PTH08000W in this situation. The max rating is more of thermal limit based on continuous use. It has over-current protection anyway, so it won't "pop", it will just shut down.

Perhaps not - but my experience working with SATCOM equipment always leads me to try to have a buffer, just in case.

No point using it in your case though since there are higher current models available for the same low price of free.

TI hates me - they won't ship over here. Kardjunkie was kind enough to send me a few TI 5G3 regulators that he had spare, so I'm good on that for the moment. Once I surprise the g/f when I go on vacation in a couple weeks, I should be able to have them send samples to the house and then forward them on to me.

 

[funkybozu]

sorry just a question here about the 5v reg 7805
what kind of batts can you use on it?
2X 3Vs or can you use 2X 3.7V batts as well?

iv read that the reg gets hot too, do you need to usea heat sink?

 

[Nuck]

sorry just a question here about the 5v reg 7805
what kind of batts can you use on it?
2X 3Vs or can you use 2X 3.7V batts as well?

iv read that the reg gets hot too, do you need to usea heat sink?

The LM7805 is a poor choice with a huge voltage drop off. It will lose up to 2.5v just to hit 5v. Your bats would have to be charged fully (2x3.7v), the (2x3.0v) would barely work at full charge, just to get to the 5v and it drops rapidly from there.

I built a bat box with that chips months ago. It works but it is very inefficient. Using a TI UCC283T-5 chip is just as easy and will give you much better results. It works well with both 3.0 and 3.7 bats and has a drop off of less than 0.5v.

The reg does get a bit warm during heavy use but nowhere near the level of requiring a heat sink.

 

[mnealtx]

In all honesty, I feel more heat from my momentary switch than from the regulator.

 

[funkybozu]

thanks nuck!

 

[Nuck]

Quick update. I built a mod that runs at several different voltages off a single bat using the TI PTN04050C that H8ISGR8 pointed out. After adding the 2 Vin and 2 Vout capacitors recommended by the datasheet (and RjG), not only have all issues with reliability gone away, the vapour output saw a steady and dramatic increase.

I used 2 low ESR 100 uF tantalum caps and 2 ceramics at 22uF. The output is not only amazing, it is rock steady throughout the entire cycle. Amazing stuff.

Thanks to H8ISGR8 for pointing out this direction.

 

[mnealtx]

How's your amp draw off the batteries, Nuck? I missed your setup - what voltage are you running?