Where to hook LED indicator?

[Dougiestyle]

The MV VV kit V2 is hooked up in my 18650 case. I had ordered an illuminated momentary from digikey, but it won't light from the board pins in the VV kit. I have other momentaries that I can use, but I need an indicator, because I incorporated a master switch on the neg leg from the batteries.

The wiring instructions shown here don't allow for an LED indicator: Variable Voltage Regulator Board Kit Rev 2

Could I hook it between pins 1-3 or 2-3? I have white 3.6v LEDs from those cheap flashlights used for mods. They worked well with my flashlight mod, but I'm stumped w/ using them in a VV.

This is the switch that's hooked up now: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=EG4683-5-ND

 

[AttyPops]

I didn't go through the diagrams/kits but basically you have two options for an indicator... 1) a power-is-on indicator, or 2) button-is-pressed indicator.

If 1) power LED - goes to v-in-before-button (+v) ->LED->Resistor->Ground (would always be on if master switch is on)
or 2) Vape LED - goes to v-out ->LED->Resistor->Ground (only on when atty active - check that it works for your lowest voltage)

Size the resistor appropriately.

Basically you have to have enough forward voltage to activate the LED at the appropriate part of the circuit and use the resister to limit current so as to not fry the LED. If you understand where and when the current is flowing, you should be able to activate the LED (including the one on the momentary switch) without too much issue. This is also why I put the resistor on the ground side of the list above... to keep the voltage drop on the ground side of the current limiting resistor.

Most LEDs need 1.5 volts.... That white one may be an exception. There's so many of em so cheap... I'd switch to another if there is an issue at lower voltage.

 

[Dougiestyle]

Your explanation is what I was thinking, but dreading. I can see the power-on indicator, but what about power drain for extended periods of power-on? The other scenario of VapeLED brings the question of which resistor? Would the LED or resistor be OK with VV? I can stand a Power-on LED if there's not too much draw and won"t kill the batteries prematurely, but ideally, I'd just like an indicator when the tact switch is depressed. Any help for a VV indicator? TIA!

I didn't go through the diagrams/kits but basically you have two options for an indicator... 1) a power-is-on indicator, or 2) button-is-pressed indicator.

If 1) power LED - goes to v-in-before-button (+v) ->LED->Resistor->Ground (would always be on if master switch is on)
or 2) Vape LED - goes to v-out ->LED->Resistor->Ground (only on when atty active - check that it works for your lowest voltage)

Size the resistor appropriately.

 

[AttyPops]

I edited the above... lol. Ok, so you want a vape-active indicator. Is the vv circuit v-in always hot, or is it after a button... in other words, do you use an inhibit pin or turn the regulator on/off every time?

Most LEDs don't take much. You could probably power the LED for months (if not years) off the batteries. Super-bright LEDs take more, tho. Just get a friggn 3mm 1.5 volt LED from something someone threw in the trash if you don't want to spend a $1.00ish at RS and then use about 1 milliamp of current to light it. That's how you size the resistor... based on max possible current and the requirements of the LED that you select.

Ohm's Law Calculator

 

[Dougiestyle]

Thanks, AP! The master switch is on the ground or neg leg of the power source. I'm guessing I'll go with a smaller LED and resistor and use a different tact switch. your answers only made obvious what I was thinking, but trying to deny lol.

 

[WillyB]

The LED part of that switch is pins 5 and 6. Pin 5 (-) can go to Pin 3 of the regulator. Pin 6 (+) will go to Pin 4 of the regulator. You need to tone down the current to the LED, so you need a resistor. The usual 470Ω MV one should work. A lower value will be brighter, higher will be dimmer.

So basically when the atty gets power that's when the LED will.

 

[Dougiestyle]

Thanks Willy!