Variable voltage mod?

[bigblue30]

Roadrash,

You are correct. The control resistor has very low current through it. In the milli amp range. In the picture below you can see the voltage is 6.57 volts. That is into a 2.2 ohm resistor. I did not want to try this with a real carto because I thought the carto would fry with that voltage. That works out to around 2.99 amps. That little 5 watt fixed resistor got ”hot” but the reg did not shut down. I know that I will have to add a heat sink in the next one I make.

 

[BuzzKill]

You can take a sheet of brass and make it fit under the electronics ( maybe put some Kapton tape or ? on it to keep it insulated )
this will help ALOT !

 

[bigblue30]

You can take a sheet of brass and make it fit under the electronics ( maybe put some Kapton tape or ? on it to keep it insulated )
this will help ALOT !

Thanks Buzzkill I will try that. I fixed my other post also. When Juicefreak talked about 3 amp POT before in his post....amp got stuck in my head. I meant to say .5 watt control resistor not .5 amp. Sorry for the confusion Buzzkill and Roadrash. That will teach me to have beer when I am BBQ'ing...lol

 

[bigblue30]

Some regulators have an internal over temp shutdown feature .
Is the Regulator .5amp ? kind of low current output for a PV , look at the AP1084 its 5 amp and variable. But it does not have a shutdown pin !

or an LT1764 it has shutdown

Have you tested this one “AP1084”? Is the spec sheet correct when it says”1.4V Maximum Dropout at Full Load Current”. That seems like a lot.

The LT1764 looks like a very neat IC. I will have to get one of these to play with. I am already using a 5 pin and the specs are very close to what I am using now…so this would fit perfect on my PCB.

 

[WillyB]

Juicefreak,

Thanks. This is my first "box" type mod. I have made a few Variable voltage PT's with this same chip, but this is my first one running on batteries.

Oh... the variable in mine is only .5 watts

Did I miss it? What reg are you using? And what pot?

And in your voltage test/pic I don't think you need to use a 'load' when when testing a regulated output, only for batteries.

 

[bigblue30]

Did I miss it? What reg are you using? And what pot?

And in your voltage test/pic I don't think you need to use a 'load' when when testing a regulated output, only for batteries.

I put the resistor on it to show I can really pull that voltage into a resistive load. Without a “real” load, in this cast a 2.2 ohm resistor simulating an atty or a carto, I could show that voltage with a few round watch batteries and a cheep adjusting POT or should I say variable resistor.

Without a load on the output of the regulator it would be like the kid I was talking to in a Honda the other day. He asked me what the red line was in my car. I told him around 6k….he laughed and said his went to 8k. I told him that until we both put a load on that engine that RPM did not matter. I guarantee him that my 6k RPM 400 HP GTO would leave his 8k RPM 200HP Honda in the dust.

Its same thing with a regulator. Until you make it work with a load nothing is proven.

 

[WillyB]

Its same thing with a regulator. Until you make it work with a load nothing is proven.

Well I'll defer to you, but a regulated power supply is supposed to be just that... regulated. Assuming you can supply the current needed by the load, the volt readings should be the same.

As an example if I drive a Joye 2.2Ω atty with a regulated 5V@3A PS, with or without the atty I should be at 5V. Now with a 5V@2A PS the atty will in fact change the volt reading.

I have some TI UCC283-ADJ, 5 pins. I know what resistors I need for my various voltages, but what pot (VR) to use is beyond me.

 

[bigblue30]

Assuming you can supply the current needed by the load, the volt readings should be the same.

You are absolutely correct that was over kill. A regulator "should" put out the same voltage with or without a load. I used the 2.2 ohm resistor to "show" not only the voltage, but to show that I could supply the current also.

I know sometimes I am a belt and suspenders guy...lol

 

[SurvivorMcGyver]

Well I'll defer to you, but a regulated power supply is supposed to be just that... regulated. Assuming you can supply the current needed by the load, the volt readings should be the same.

As an example if I drive a Joye 2.2Ω atty with a regulated 5V@3A PS, with or without the atty I should be at 5V. Now with a 5V@2A PS the atty will in fact change the volt reading.

I have some TI UCC283-ADJ, 5 pins. I know what resistors I need for my various voltages, but what pot (VR) to use is beyond me.

50K should work just fine down to around 5V, 100K (76.530612244898 Kohm) to getter down to 3.7 (which I have yet to try -- but that's what the formula gives me) -- They all will get you max bat less abount 0.5 volts or so Max.

Note: My experience is with the UCC383-ADJ version.

Sub Note: Try testing AT THE ATTY under load some time. You just might find some surprising results to your tests .......

Sub Sub Note: All calcs are used with R2 a 150k PER THE TI spec sheet

 

[bigblue30]

I have to ask a question….. Why are all (almost all) the mods I see ether fixed voltage ie. 3.7, 5, 7.4 or they use a switch to select a voltage from a 7.4 volt pack ie. 4.2, 4.5, 5.0,….?

I have been looking around the board for a few weeks and every time someone talks about making a variable mod or starts a thread about using the IC chip that will make a variable mod…..the thread dies a quick death.

I am not looking for info on how to do this. I already have a box mod that is variable from 2.5 volts to around 7 volts using (2) 14500’s

I am kind of new here and do not want to step on anyone’s toes. Any info will be appreciated.

Thank you to all that have help me answer my original question. I appreciate it. I will be starting a new thread later today with a parts list and a schematic of my adjustable voltage mod.

 

[Switched]

Well I'll defer to you, but a regulated power supply is supposed to be just that... regulated. Assuming you can supply the current needed by the load, the volt readings should be the same.

As an example if I drive a Joye 2.2Ω atty with a regulated 5V@3A PS, with or without the atty I should be at 5V. Now with a 5V@2A PS the atty will in fact change the volt reading.

I have some TI UCC283-ADJ, 5 pins. I know what resistors I need for my various voltages, but what pot (VR) to use is beyond me.

That has been my experience as well

 

[bigblue30]

I have started a new post with the schematic, parts list,and pictures of my MOD.


http://www.e-cigarette-forum.com/forum/battery-mods/102419-adjustable-voltage-box-mod.html

I want to thank all of you that answered my original question and have given me great feedback.