help adding USB pass option to box mod

[KarrMcDebt]

I have a mini usb connector and would like to add it to my box mod so that the mod can be used as a usb passthrough. (mod is 2x14500 series w/ 5v regulator).

Do you need to add diodes to the battery lines to protect them from the incoming voltage? If so do you need one on each leg ( + and -) or only on the +?

Thanks
Karr

 

[Rocketman]

karr,
the 5 volt usb wouldn't be able to charge the series batteries, so no need to connect the usb + lead there.

the 5 volt usb wouldn't be able to go into the regulator and and still give 5 volts out, so no need to connect it there.

the 5 volt usb would not be enough voltage to damage the regulator or go backwards if connected to regulator output, connecting here would be OK.

the 5 volt regulator output would not be high enough to damage the usb circuit if you left the usb connected.

Soooo,
5 volt USB connected to output of 5 volt regulator.
Vape and some of the current might come from the USB and some from the regulator. Would almost be like having two 5 volt sources connected together.
If the USB was a little above 5 volts (unloaded, most are) then it would be sucked down to regulator voltage then both would be supplying current.
Problem would be if batteries got low the USB power would "mask" it.
You are using protected 14500 cells, right?
Part of the safety aspect of vaping stacked batteries is the experienced vaper 'feels' how the mod is performing. Unbalanced battery cells, are hard to 'feel'. Masking this even further with an axillary power source would be like 'flying blind'.


Rocket

 

[KarrMcDebt]

Nice, not only answered my question, but added a couple things I hadn't thought of.

Realy I wanted it for a usb pass when the batterys are in the (seperate) charger.

The only non-protected cells I own are the cr123 rechargables for my surefire flashlight.

I'll never chance it again after I had one meltdown due to a short circuit.

Thanks
Karr

 

[KarrMcDebt]

Ran into a snag. If I connect the usb port like described, the atty gets constant power. I have the momentary switch and the master switch before the regulator, so now I'm back to the same question.

Can I protect the batterys from the usb power by adding a diode to both of the lines from the batterys to the regulator, (one each direction)? The regulator should have no problem taking the 5v, I'm just worried about the bleed back to that batts.

Karr

 

[karmatized]

use a 4 pin on off switch when the unit is off position it disconnect battery and allows full usb usage. When it is in the on position its battery usage. There not combined in any way, and manage everything though either positive or negative lines. This way no connection makes a circuit into the other device.

 

[KarrMcDebt]

Good call.

It will mean that I won't be able to do it with the mod I have in mind, but I'll definately be incorporating it into a future mod.

 

[Rocketman]

karr,
using 3 pin or 4 pin regulator?
With a 3 pin, master switch could turn on regulator, momentary controls power to atty (after regulator, and after usb power). The usb connection after atty would work if switch was after regulator and USB power but before atty.

With 4 pin regulator the momentary is not in atty current path. USB to input of regulator would give a little less than 5 volts out of regulator but control pin would control atty current.

The original question about diodes: One diode is all that would be needed if a good point can be found to insert it.
If 3 pin regulator and usb power is applied after regulator then followed by switch no diode needed.
If 4 pin regulator and usb power applied to input of regulator you end up with a tie point for battery +, usb +, and regulator input.
The 5 volts from the usb won't flow into higher voltage of the stacked 14500 batteries but the battery voltage can flow into the usb source. USB probably wouldn't like that. If you put a diode to block this current then you lose 0.6 volts from the USB.
If you are using the 4 pin regulator, then another switch is probably best. If could even be a SPDT slide switch with 3 positions, USB-OFF-Battery.

Hard to get these things to do everything. I'm still waiting for one with an MP3 player built-in.

Hope I didn't cause you to fry an atty.

Rocket

 

[KarrMcDebt]

That particular mod is running a 3 pin regulator from rat shack.
I can rewire the switch but normaly I prefer the momentary switch to be before the regulator, then the regulator only has power to it when you push your button.

Nope, didn't cause any damage. My momentary has a LED in it, (wired for momentary).
I knew something was wrong when the led went on and stayed on.

 

[KarrMcDebt]

I figured out how to do it. The standard switch on these battery boxes normaly are connected to the ground. The switch is actualy a two position switch (center and left/center and right). Rewire the ground dirrectly from the negative battery terminal to the negative connection on the regulator, wire the positive wire from the battery to the right contact on the "Master" switch, wire the left contact on the "Master" switch to the USB positive wire and run out from the center to the positive input on the regulator.
The switch is no longer an on/off switch but a USB/Battery switch, but still functions as a on off switch when the usb cable is disconnected. When it is connected it will isolate the battery from the USB power, and vice versa.

Then I still get to keep the momentary and the "Master" switch before the regulator. If the momentary switch is wired after the regulator, it means that the regulator always has power running through it when the master switch is on.

I belive that placing the momentary switch before the regulator you reduce power usage, reduce heat production and extend the life of the regulator, as well as reducing the load on the batterys, which would reduce the risk of battery explosion. When coupled with protected batterys this should all but eliminate the risk.

Karr

 

[WillyB]

I figured out how to do it.

I belive that placing the momentary switch before the regulator you reduce power usage, reduce heat production and extend the life of the regulator, as well as reducing the load on the batterys, which would reduce the risk of battery explosion. When coupled with protected batterys this should all but eliminate the risk.

Karr

That's the correct way to do it... period.