Variable Voltage Circut Diagram

[mcquinn]

Anybody willing to give up a variable voltage circut design and parts list that I can use in my passthroughs?

[Jolly]

to build this you only need two different things to add to a straight threw pt

this http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&site=ca&keywords=679-1874-ND&x=22&y=15

and a resistors attached to the pegs you will use on the slid swith to drop the 5v.

you could even use a ego battery sized pvc pipe to build it so that there is room for the slid switch.

[benjamin1990]

i have made two passthroughs now and i just wire the positive to the switch and off the switch to the positive post. then take the negative and wire it to the negative threads and i use and enercell charger and i can change the voltage from 3,5,6,6.5,7,7.5. and the voltage is spot on! i love it it works out great. but thats just me.

[mcquinn]

Thanks Jolly I am for sure not an electronics guy.Mine were straight thru 5 volts and I didn't like the 5 volts so I never used them.I put a resister on one and got it to 4 volts but I was thinkin of modifiying another variable.

Edited August 29, 2010 by mcquinn

[Jolly]

you have any vary-mods other than that so far?

i'm going to build a compact single cell vary. just waiting on the parts to come in.

uses a single cr123a. tube design.

[mcquinn]

Not yet ,I don't really plan on varying the voltage once I find one I like ,I am just trying to find a way to use my homemade passthroughs.I think 3.7 to 4 volts is what I prefer.I was curiouse what the variable circut they are using in mods looked like as the resistor I used to get 4 ohms was pretty large,it would fit in a passthrough but I was hoping there was a better way.

[Brian]

This link had been posted a long time ago... don't know if anyone ever used it. Seems a little pricey, but just FYI.

My link

[mcquinn]

That would be very nice,it would fit in one of my passthroughs but probably not a battery mod.I agree $25.00 is kinda rich .Saving for future reference.The aerospace engineers on my other forum seem to think I need to use the larger wire wound resistors as the current would exceed the ability of the smaller carbon type.It was kind of fun reading thier technical explanations ,a lot of info flew right over my head though.

Edited August 29, 2010 by mcquinn

[WillBlack]

to build this you only need two different things to add to a straight threw pt

this http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go〈=en&site=ca&keywords=679-1874-ND&x=22&y=15

and a resistors attached to the pegs you will use on the slid swith to drop the 5v.

you could even use a ego battery sized pvc pipe to build it so that there is room for the slid switch.

That ain't gonna work. This is the key reason:

Contact Rating @ Voltage 0.3A @ 125VAC

Mcquinn wants a lower volt device, but he still needs something that can handle about 2A (2000mA) just to be safe. As far as using resistors they will have to be able to shoulder some of the WATTS, 5W ones should work. These tend to be a bit large.

That would be very nice,it would fit in one of my passthroughs but probably not a battery mod.I agree $25.00 is kinda rich .Saving for future reference.The aerospace engineers on my other forum seem to think I need to use the larger wire wound resistors as the current would exceed the ability of the smaller carbon type.It was kind of fun reading thier technical explanations ,a lot of info flew right over my head though.

There is nothing overly technical about resistor wattage. 5V with a 2.2Ω atty produces about 11.4W, 3.7V about 6.2W. Subtract and you get the approximate amount of watts the resistor needs to absorb, about 5.2W (to make that jump). Hence the need for large power resistors.

You asked for a diagram. Here's one of BigBlue's that I've butchered (simplified actually).

This is using a 5 pin TI LDO adjustable regulator. Assuming you are using a solid 5V power supply this reg has a drop-out voltage of .5V (loses that much). That means the highest output will be 4.5V which should suit you fine. Where it says '200k 1/2W' that's a trimmer capacitor. If you get a 25 turn one your voltage changes will be very precise and small. You'll probably be able to drop by 0.1V increments. The 2nd cap on the output side is not really needed you can omit that.

If you really think you want to tackle it I'll provide more info.

FWIW the SWADJ3 that Brian linked to is well worth the money, I'd buy it in a heartbeat. With less than $10 in additional parts you'd have a dynamite mod. The case could probably be removed and it would probably fit in a AA plastic box. But unfortunately the vape time would be very short due to this spec:

1.2V typical dropout voltage, 2.0v maximum at full load

What that means is someone vaping @ 5V with the TI LDO's is good to go until the batts drop to 5.5V. With the SWADJ3 the same vape will only last till the batts get to 6.5V. If you used it with a 5V power supply the max output would only be about 3.5V.

Edited September 5, 2010 by WillBlack

[mcquinn]

Hmm got the wheels turning.Are those electrolytic or tantalum capacitors?Tantalum would be smaller I think.It says trimmer 200K 1/2 watt capacitor ,would that be a trimmer resistor?I have not bought much electronic supplies for quite a few years ,Radio Shack does not seem to have much any more,Where do you order from?

Edited September 5, 2010 by mcquinn

[miatafrank]

Try this selector guide

http://www.nteinc.com/Web_pgs/Adjustable.html

[WillBlack]

Mouser seems like good place. BigChev went with the tantalums, I did up the volts to 16 from his 10V. Reading the spec sheet for the correct caps is a maddening experience. But I think in our case, battery input and a simple resistive load (the atty) we don't have to be so technical.

The chip (or get some samples):

http://ca.mouser.com/ProductDetail/Texas-Instruments/UCC383T-ADJ/?qs=sGAEpiMZZMsGz1a6aV8DcPXeWoVS0FnzOQaH6Ohm4sY%3d

One trimmer that should work.

http://ca.mouser.com/ProductDetail/Bourns/3296Z-1-204LF/?qs=sGAEpiMZZMs26uXuX7MLMRCLxTj8FVH7

http://ca.mouser.com/Passive-Components/Trimmer-Resistors/Trimmer-Resistors-Multi-Turn/_/N-76qcu?P=1z0vko6Z1yzuvtx

Caps. These should do it.

http://cgi.ebay.com/10-uF-25-Volt-Tantalum-Capacitor-10-each-/220332871874?pt=LH_DefaultDomain_0&hash=item334cdcd0c2

http://shop.ebay.com/i.html?LH_FS=1&_trkparms=65%253A12%257C66%253A1%257C39%253A1%257C72%253A3983&rt=nc&_nkw=TANTALUM%2010uf&_trksid=p3286.c0.m14.l1581&_pgn=2

I'll find the link to Big's guide.

Edited September 5, 2010 by WillBlack