Some Electrical Help Needed

[u_couple]

Hi guys, hopefully someone will be able to help me out here !
I have built a couple of mods using the diagram from raidy`s thread here http://www.e-cigarette-forum.com/fo...you-even-use-smallest-switch.html#post2106279

I have very little electronics knowledge, so basically followed this diagram to the letter, on one of the mods, I used one of those round head, clicky tactile switches, and added an LED. Both mods work perfectly, apart from the one with the LED, which, as soon as I connect an atomizer, the LED glows, very faintly.
I took it all apart, and re-wired it again, just in case I had a wire touching or something, and it`s still doing it!! every time I connect an atty (and I`ve tried a few) the LED glows very faintly, I`m not clever enough to figure this one out, but hopefully someone here will be able to tell me where I`m going wrong

 

[Scubabatdan]

First did you remove the 1k resistor? It is not needed with a tact switch. And dropping the 4M to a 47k resistor between the Gate and Source?
Second where are you adding in the LED? (LED) Ground leg to (Mosfet) Drain leg and (LED) Positive leg to Pos battery?
I.E.

Dan

Added, of course the LED resistor is dependent on the battery V, LED V and mA. This is based on a 3.7V battery, 3.2V LED with a max load of 35mA.

Thanks slimest for keeping me inline

LED calculator for resistor: http://ledcalculator.net/
Dan

 

[slimest]

I think, in the schematic above LED will be burnt in seconds... Needs a resistor in series.

If TS got voltage drop with atomizer connected, the first questions are:
- what mosfet do you use?
- what battery do you use?
- what switch do you use?

 

[Scubabatdan]

I think, in the schematic above LED will be burnt in seconds... Needs a resistor in series.

If TS got voltage drop with atomizer connected, the first questions are:
- what mosfet do you use?
- what battery do you use?
- what switch do you use?

LOL I knew I forgot somthing hehehehe.... Will amend.
Dan

 

[u_couple]

Thanks guys, I`m gonna try again using the above diagram, much appreciated

Can I just ask Dan, in the above diagram, are you wiring the pos leg of the LED to the pos wire, and putting the 15k resistor on the neg leg?

 

[Scubabatdan]

Thanks guys, I`m gonna try again using the above diagram, much appreciated

Can I just ask Dan, in the above diagram, are you wiring the pos leg of the LED to the pos wire, and putting the 15k resistor on the neg leg?

Correct, pos leg of LED to pos of battery and neg leg of LED to resistor, resistor to Drain from mosfet.
What is the mosfet part number by the way?
Dan

 

[u_couple]

I went for the mosfet that raidy recommended, the IRL3103

 

[slimest]

u_couple, as far as I understand your LED glows OK without atomizer and gets dim after atomizer connection. If so, your system loses voltage somewhere. If you use correct MOSFET, you should concider bad contacts in power circuit, bad battery (yes, some batteries have high internal resistance and cannot supply high currents) or bad switch. Your switsh has to supply maximum voltage on MOSFET gate, it should be the same as battery voltage. If not, MOSFET does not open fully, and you loose voltage on output.
In any case you can use any voltmeter to troubleshoot. No need in special knoledge, just logic.
Hope, my bad english is clear enough.

Scubabatdan, you can afford to forget something. You give great help to many people