Adjustable voltage box mod

[misterD]

thanks, bigblue but what i need is a POT to go with that 5V booster. or should i just use the resistors like on the fistpack?

 

[bigblue30]

Sorry, I thought you were asking for the chip.... I seem to have a problem understanding what people say today...lol.

The variable res looks like this:

POT 200K OHM 3/4" RECT CERM MT - 3009Y-1-204

OR like this this:
variable resistor for sale

This is the one (3rd one down) I use because it fits on a PCB board better.

What Ohms are you looking at. 200k might not be correct.

Any electronic shop should have ones like this

 

[misterD]

just wanna thank BigBlue for everything. i ordered some stuff out of digikey to build a fistpack (less enclosure and mom switch) and 2 POTs.
i wanna have a bottom feed box with variable voltage. i have my bottle feeding system working acceptably great and i think it be nice to have it go variable voltage!
these POTs have a life cycle of 200 turns. does it mean if you keep turning back and forth its gonna give up one day? thats what might keep me from getting a BUZZ. if i have the POT in a box i can just replace it when time comes. if the variable on the BUZZ fail after 6 months what am i to do? i love when somebody elses post actually pushes me to try to build something its been awhile since it happened last! thanks again, BigBlue!!!!

 

[o4_srt]

looks great!

The only thing I have to comment on is the switch.

The way you wired the switch, wouldn't it be possible to throw it in a pocket, or purse, or somehow depress the button unknowingly, possibly causing an overdraw, or thermal issue with the batteries?

The aesthetic value of only one switch is nice, but I would think that having a separate switch for VCC would be much more safe.

 

[WillyB]

just wanna thank BigBlue for everything. i ordered some stuff out of digikey to build a fistpack (less enclosure and mom switch) and 2 POTs.
i wanna have a bottom feed box with variable voltage. i have my bottle feeding system working acceptably great and i think it be nice to have it go variable voltage!
these POTs have a life cycle of 200 turns. does it mean if you keep turning back and forth its gonna give up one day?...

The FistPack uses a PTN04050C booster. It operates differently than biggie's regulator. Naked they pump out 5V, adding resistors raises the voltage over 5V. That's why the final diode is important to bring the adjusted voltages back down by a factor of about .7V. In other words if you are looking for about 5V max volts you'll need a 34.5kΩ resister which should initially provide about 5.8V. It would also appear that you do not want your Vout to be less than 4V as this may damage the booster. So some care will be needed with a pot.

 

[misterD]

so its the diode that does the magic? its the same one nuck listed on his tutorial, right? what i wanna try is having a POT in place of those 3 resistors and sliding switch. do you think it'll work ok with the 200K POT? if i add that 100K resistor between Vout and Adj is it safe to use LR attys? i know! its just that i have too many LR's...
thanks WB!

 

[bigblue30]

The FistPack uses a PTN04050C booster. It operates differently than biggie's regulator. Naked they pump out 5V, adding resistors raises the voltage over 5V. That's why the final diode is important to bring the adjusted voltages back down by a factor of about .7V. In other words if you are looking for about 5V max volts you'll need a 34.5kΩ resister which should initially provide about 5.8V. It would also appear that you do not want your Vout to be less than 4V as this may damage the booster. So some care will be needed with a pot.

MisterD, WillyB is correct. I learned a LOT from him. You use the FistPack when you only are going to use 1 (3.7 volt) battery and you want more then the 3.7 volts that one battery puts out. You use mine when you want to use (2) batteries and you want to adjust the voltage DOWN from the 7.4 volts that 2 batteries put out.

And to answer your other question about the variable resistor... they are rated at 200 FULL turns. I have talked to a few suppliers and they say that is the minmum...If you are like me, you will play with the voltage at first until you find your "sweet spot"....then not use it as much.

 

[misterD]

im gonna use a single 18650. its gonna be a fistpack JB with a POT instead of a sliding switch and fixed resisters!
https://docs.google.com/Doc?docid=0AXdaMZo4FKMVZGhqdnE4YnNfNDNjN2Q0cHBoZg&hl=en

 

[bigblue30]

looks great!

The only thing I have to comment on is the switch.

The way you wired the switch, wouldn't it be possible to throw it in a pocket, or purse, or somehow depress the button unknowingly, possibly causing an overdraw, or thermal issue with the batteries?

The aesthetic value of only one switch is nice, but I would think that having a separate switch for VCC would be much more safe.

O4_SRT, YES, two switches are much safer. that is my "belt and suspenders" one from my post:

3. Have a high quality ‘kill” switch and a separate high quality “fire” switch. This makes it very “safe”. Both switches have to fail to get a miss fire. The kill has to short and the fire has to open. I know nothing is fool proof. This is as fool proof as possible with this chip, This is the belt and suspenders one.

BUT the only problem is...if you forget to turn off the "safety" switch and put it in your pocket. You then have mill amps flowing through the mod and a greater chance for a "misfire" if you hit the "fire" button by mistake.

I am still going back and forth with this.

 

[o4_srt]

O4_SRT, YES, two switches are much safer. that is my "belt and suspenders" one from my post:

3. Have a high quality ‘kill” switch and a separate high quality “fire” switch. This makes it very “safe”. Both switches have to fail to get a miss fire. The kill has to short and the fire has to open. I know nothing is fool proof. This is as fool proof as possible with this chip, This is the belt and suspenders one.

BUT the only problem is...if you forget to turn off the "safety" switch and put it in your pocket. You then have mill amps flowing through the mod and a greater chance for a "misfire" if you hit the "fire" button by mistake.

I am still going back and forth with this.

how would leakage occur when using a regulator with a control pin? no current can flow through the regulator, to ANY part of the circuit, until the regulator gets the signal (through the momentary switch, normally open) to turn on.

 

[bigblue30]

how would leakage occur when using a regulator with a control pin? no current can flow through the regulator, to ANY part of the circuit, until the regulator gets the signal (through the momentary switch, normally open) to turn on.

Are we are talking about my circuit? I know the FistPack chip has been thrown in here.

I was talking about my circuit using the UCC383 or UCC283 chip when I answered you.

"I said "BUT the only problem is...if you forget to turn off the "safety" switch and put it in your pocket. You then have mill amps flowing through the mod and a greater chance for a "misfire" if you hit the "fire" button by mistake."

I should of said uamps not millamps

There are two switches in my circuit: one “safety” switch (the switch that goes between the battery and the circuit, it is a normally open switch), and one “fire” switch (it is a normally CLOSED switch that tells the regulator to turn on when it is opened.)

If you forget to turn the safety switch off and you put it down or in your pocket then you have this….. At rest…with no output from the regulator…with the safety switch on and the fire switch closed (N/C) there is still current flowing through the chip…from the TI spec sheet it says …” Quiescent current No load 400 to 650 ua””. So any time you turn on the safety switch there is current flowing to the chip. You are correct thinking that no current flows from the output to the addy, but current is still flowing through the “input “side”.

 

[bigblue30]

just wanna thank BigBlue for everything. i ordered some stuff out of digikey to build a fistpack (less enclosure and mom switch) and 2 POTs.
i wanna have a bottom feed box with variable voltage. i have my bottle feeding system working acceptably great and i think it be nice to have it go variable voltage!
these POTs have a life cycle of 200 turns. does it mean if you keep turning back and forth its gonna give up one day? thats what might keep me from getting a BUZZ. if i have the POT in a box i can just replace it when time comes. if the variable on the BUZZ fail after 6 months what am i to do? i love when somebody elses post actually pushes me to try to build something its been awhile since it happened last! thanks again, BigBlue!!!!

MisterD,

I wanted to answer your question here also.

I called Bourns: ( http://www.bourns.com/Products.aspx ). As you can see from their site they are a very big supplier. They make most of the pots we are talking about.

At first I was told that the life of the pot was 200 full turns…..That was not accurate. I then asked to talk to the “head” engineer. He sent me the e-mail that is below.

Here is the response from the engineer.

"One cycle for 25 turn pot is 25 turns there and back; total of 50 turns, so rotational life is 10,000 turns. Failure from rotational life would be from wiper wear, which would be an increase in contact resistance between the wiper and resist ink, higher CRV and inevitably open circuit."

 

[WillyB]

how would leakage occur when using a regulator with a control pin? no current can flow through the regulator, to ANY part of the circuit, until the regulator gets the signal (through the momentary switch, normally open) to turn on.

If you use MadVapes 4 pin Fairchild regulator (per the diagram), if the kill switch is on you are using current, whether you are pressing the momentary switch or not.

Here is the response from the engineer.

One cycle for 25 turn pot is 25 turns there and back; total of 50 turns, so rotational life is 10,000 turns. Failure from rotational life would be from wiper wear, which would be an increase in contact resistance between the wiper and resist ink, higher CRV and inevitably open circuit.

SO, The worst thing that would that would happen is this…..The pot would “open” (like it was not there) and the chip would default to its lowest adjustable voltage, and you would not be able to change it.

In my curcuit if this happens the output will default to 5 volts.

Great info big, thanks.

 

[Mr.Mad]

Have you guys seen the little sister yet adjustable voltage and very small... I gonna order one just too see how it works. it has varible voltage from 3.7 up too like 6.5 I love it.

YouTube - Little Sister MOD!

 

[bigblue30]

If you use MadVapes 4 pin Fairchild regulator (per the diagram), if the kill switch is on you are using current, whether you are pressing the momentary switch or not.



Great info big, thanks.

Thanks WB...

 

[roadrash]

MisterD,

I wanted to answer your question here also.

I called Bourns: ( http://www.bourns.com/Products.aspx ). As you can see from their site they are a very big supplier. They make most of the pots we are talking about.

At first I was told that the life of the pot was 200 full turns…..That was not accurate. I then asked to talk to the “head” engineer. He sent me the e-mail that is below.

Here is the response from the engineer.

"One cycle for 25 turn pot is 25 turns there and back; total of 50 turns, so rotational life is 10,000 turns. Failure from rotational life would be from wiper wear, which would be an increase in contact resistance between the wiper and resist ink, higher CRV and inevitably open circuit."



SO, The worst thing that would that would happen is this…..The pot would “open” (like it was not there) and the chip would default to its lowest adjustable voltage, and you would not be able to change it.[/FONT]

In my circuit if this happens the output will default to 5 volts.

Thanks BB for posting this info. helps a lot.

 

[misterD]

i would like to thank you over here also. the box that i'll be doing is for the most part your fault.
im gonna be getting my parts from digikey tomorrow. i have carved the box for the mini usb, the switch and my connector. tomorrow i'll get the resistors, diode, pot... i kinda have the bottom feed system done also. the hard part is yet to come i want it to work well so i'll take my time with the soldering iron. i'm afraid i'm gonna get really mad at it (and at myself) and all the tiny parts.
So, THANK YOU BB!!!

 

[bigblue30]

i would like to thank you over here also. the box that i'll be doing is for the most part your fault.
im gonna be getting my parts from digikey tomorrow. i have carved the box for the mini usb, the switch and my connector. tomorrow i'll get the resistors, diode, pot... i kinda have the bottom feed system done also. the hard part is yet to come i want it to work well so i'll take my time with the soldering iron. i'm afraid i'm gonna get really mad at it (and at myself) and all the tiny parts.
So, THANK YOU BB!!!

You are very welcome misterD....Take your time and all will turn out OK. If I can do it....a 55 year old with a 30 year old Weller pencil soldering iron with a crappy tip...anyone can do it.

I have to ask Santa for a new solder station....lol

 

[misterD]

sorry! how do i wire this POT? it has 3 pins (1, 2, 3) i presume that 2 is ground and then i wire one of the others to Adj.

 

[bigblue30]

sorry! how do i wire this POT? it has 3 pins (1, 2, 3) i presume that 2 is ground and then i wire one of the others to Adj.

Yes. You can use pin 1(outside) and 2(center pin) and leave pin 3(outside) disconnected or use pin 2 and 3 and leave pin 1 disconnected. It makes no difference. I normally connect pin 2 of the POT to adjust and then pin 2 or 3 of the POT to pin 1 (ground) of the chip.



WillyB added this to the post:

The FistPack uses a PTN04050C booster. It operates differently than biggie's regulator. Naked they pump out 5V, adding resistors raises the voltage over 5V. That's why the final diode is important to bring the adjusted voltages back down by a factor of about .7V. In other words if you are looking for about 5V max volts you'll need a 34.5kΩ resister which should initially provide about 5.8V. It would also appear that you do not want your Vout to be less than 4V as this may damage the booster. So some care will be needed with a pot.

WillyB knows this chip a lot better then I do. You might want to ask him what this means by this:

It would also appear that you do not want your Vout to be less than 4V as this may damage the booster. So some care will be needed with a pot.

I think what he is saying is you want to be careful not to let that POT go too low in resistance. WillyB please correct me if this is wrong.


The picture shows a “fixed” resistor in line with pin 2 of the POT. This will ensure that the adjustment of the POT never goes below the value of the fixed resistor.

When using the boost chip you add “less” resistance to the adj (pin 3) to increase the output voltage.

So...with this "fixed" resistor you can be sure that the output voltage will not go too high.