DNA20 firing button question

[Azmo]

I'm getting ready to build my first DNA20 mod and have a question. I am going to use an anti-vandal button with a 3v LED in it. My question is, being that the battery will meter at 4.2v when fully charged, should I use a resistor for the LED?

I'm not sure if that little increase in voltage will cause the LED to burn out that much faster. And if I use a resistor to drop it from 4.2v to 3v, will the LED not light once the battery gets down to 3.9v? Or is there a pretty wide range on LED voltage?

 

[xpen]

I think to remember that LEDs are sensitive to current more than voltage, so yes a resistor sounds like a good idea.

I was also thinking about a zener diode, which may effectively cut any voltages beyond a given threshold, but a resistor should be there anyway for current limiting purposes.

Alas it's been a looong time since my electronics 101, so I may be wrong here...

I'm getting ready to build my first DNA20 mod and have a question. I am going to use an anti-vandal button with a 3v LED in it. My question is, being that the battery will meter at 4.2v when fully charged, should I use a resistor for the LED?

I'm not sure if that little increase in voltage will cause the LED to burn out that much faster. And if I use a resistor to drop it from 4.2v to 3v, will the LED not light once the battery gets down to 3.9v? Or is there a pretty wide range on LED voltage?

 

[LucentShadow]

Are you going to connect the firing switch to it's place on the circuit board? If so, I doubt that the circuit would drive the LED, though I can't find any specific info as to what voltage and current are applied the firing swich, other than 'low power'.

http://evolvapor.com/wp-content/uploads/dna20.pdf

Otherwise, I'd add a resistor to any LED, though I'd expect something with a built-in LED to have some sort of current-limiting component (though I wouldn't necessarily be surprised if it didn't.) Not sure how easy it'd be to get one in there, either.

 

[Azmo]

If I am not mistaken, the button is between the battery and the board. So the full battery voltage would pass through the button.

 

[LucentShadow]

Well, I'm not sure of the design that you are looking for, but the DNA20 has a built-in fire button, as well as two adjustment buttons. These can be bypassed by soldering one's own button onto the board's interface. That's pins 11 & 12 on the board for the fire button. I'm not sure if there is any easy way to use any other on/off method.

This is a logic function that lets the circuit know to turn on the output, so is a low-power branch of the circuit. It's explained a bit vaguely near the end of the datasheet link that I posted earlier.

 

[Azmo]

Ahhh, I see that. I should have paid more attention to that. I guess I will just use the switch I have and not wire the LED. I don't want to pass any voltage through the board that could damage it.

For the LED, I would need a lead from the battery to one side of the LED and the other side would just be jumped to the normally open side of the switch. That way the LED would come on when the button was pressed. But that would also put the full voltage of the battery into the circuit board.

 

[LucentShadow]

Hmm. I've not considered using an LED with the DNA20. I don't see any simple way to do it, as the output has too much range to use that. I suppose a DPST switch could run the fire circuit on one pole and an LED between battery posts on the other pole. Maybe a MOSFET could be used with the fire switch to drive an LED, too.

I guess that most just settle for the screen function. Not sure if anyone's added an LED, though.

 

[Azmo]

I just wanted it to look sexy. It wouldn't serve any other purpose. I did send Evolv an email though to see if it was possible.

 

[retird]

You could wire a LED on the wire going to the atty connector......

 

[Azmo]

You could wire a LED on the wire going to the atty connector......

How would that wiring go when one side of the LED has to be wired to the normally open side of the switch? Wouldn't that still allow voltage to flow to the board?

 

[DrMA]

I'm not sure this is entirely possible unless you build a separate circuit for the LED that does not have continuity with the DNA board.

 

[mezzio]

You could wire the LED on the board side of the switch between the board and the switch. Pick up a 5V LED which you're at it, that way you're not stuck with 19 extra resistors you'll never use. It won't be affected by the boards variable voltage and wattage, it'll stay at or below whatever the battery is pumping in.

If you put the LED between the board and Atty, you'll need a separate circuit to control the voltage to the LED so you don't pop it when you crank it to 6V, lol.




Sent from my Google powered personal data extraction device

 

[Vapant]

This circuit is working for me.
http://www.e-cigarette-forum.com/fo...illuminated-switch-led-dna20.html#post9528169
I tend to cover the illuminated part of the switch with my finger anyway so not much use for me after all, but if you put your scren on the inside, the LED may be of some use.