Check My work Nicostick Mod

[Kewtsquirrel]

Woot! I tried to draw you a diagram earlier, but I'm on my laptop and a horrible artist, so it looked sort of like a 3 year old scribbled on my monitor and wasn't much use.

Next up: 5v regulated mod so you can join the big boys club! ^_^

 

[Wagex]

i used a 1m ohm on my mosfet to shut it off theyare 99 cents at ratshack for a pack of 5 mine was toutch idk if that makes a difference

 

[Kewtsquirrel]

Nope, anything over a few k ohms is perfectly fine, you just don't want you use a low ohm resistor or you completely negate the effect of the mosfet - the whole point is drive almost no current through the physical switch.

 

[UberSquid]

I'm confused on the MOSFET. How does one go about selecting one that is appropriate? Also, I can't visualize how the resistor goes on. I drew out a schematic but can't get mine to work.

 

[UberSquid]

Just figured out where the resistor goes and why.

 

[Kewtsquirrel]

On appropriate mosfets, you want one with the lowest R(ds)on you can find, and that can handle at the very least 3A.

 

[UberSquid]

I'm using a TIP31A which looks like it should work. I ran positive, through atomizer to the Collector. Emitter to ground with a 4.7K resistor inline and then switched power to Base. Is this correct? It won't fire my atomizer.

 

[ajduran]

I'm using a TIP31A which looks like it should work. I ran positive, through atomizer to the Collector. Emitter to ground with a 4.7K resistor inline and then switched power to Base. Is this correct? It won't fire my atomizer.

I'm not much of an electronics expert but since nobody else answered I thought I'd give this one a shot.

A while back I did some experiments with a TIP31 because I had one on hand. Here's what I used:

Pos -> atty -> collector
Emitter to neg
Pos -> switch ->39 ohm resistor (1/2 watt) ->base

I figured I'd need a 47 ohm resistor. I tried 68 and 39 that I had on hand. Either way it worked but put about 50mA less through the atty than powering the atty directly from the battery. There is a small voltage drop through the collector/emitter junction and this may be the reason. Somebody with more knowledge could probably say for sure.

 

[UberSquid]

what the hell? It seems like the LED's that I installed with my box are screwing up my MOSFET! At first I had a floating gate issue so I put a resistor inline with ground. My LEDs are all parallel but for some reason they are making weird things happen like I get funky voltage readings at the atomizer. Also I am getting a lot of voltage drop at the atomizer now. I started off with 4.6 volts from a 5V source and I'm down to .8V now! I can't find any reference materials that I can understand on how to use these MOSFETs. I don't have a degree in electrical engineering (I'm in structural engineering) so I really don't know how to apply the formulas to do this right. Is there any TLA reference around on how to make this work?

Thanks

Jeremiah

 

[Marctwo]

I'm using a TIP31A which looks like it should work. I ran positive, through atomizer to the Collector. Emitter to ground with a 4.7K resistor inline and then switched power to Base. Is this correct? It won't fire my atomizer.

E should be going straight to V-, not through a resistor.

The way I do it:
Atty+ > V+, Atty- > C
LED+ > V+, LED- > Res(470/1K/???) > C
B > Res(47K/1M/???) > E > V-
B > sw > V+

 

[UberSquid]

translate please...

Atty+ > V+, Atty- > C
LED+ > V+, LED- > Res(470/1K/???) > C
B > Res(47K/1M/???) > E > V-
B > sw > V+

 

[Marctwo]

It may look complicated but it's realy not. Unless there's a particular term used that you can't work out?

 

[ajduran]

what the hell? It seems like the LED's that I installed with my box are screwing up my MOSFET! At first I had a floating gate issue so I put a resistor inline with ground. My LEDs are all parallel but for some reason they are making weird things happen like I get funky voltage readings at the atomizer. Also I am getting a lot of voltage drop at the atomizer now. I started off with 4.6 volts from a 5V source and I'm down to .8V now! I can't find any reference materials that I can understand on how to use these MOSFETs. I don't have a degree in electrical engineering (I'm in structural engineering) so I really don't know how to apply the formulas to do this right. Is there any TLA reference around on how to make this work?

Thanks

Jeremiah

So what are you using now? Didn't you say you were using a TIP31 before? A TIP31 is a power transistor and not a MOSFET, which are not the same thing and are wired a little differently.

More info required.

 

[ajduran]

And, how many LED's are you using? One? Sounds like you are using more than one. There are lots of different LED's and all have different forward voltage drop and this must be considered especially if you are using more than one.

 

[ajduran]

OK, I forgot you wrote you have your LED's in parallel; still there is not enough information here. Are you using a transistor or MOSFET? How is everything wired?

 

[UberSquid]

I'm using the TIP31 but didn't realize at the time it was a transistor! Now knowing that it's a transistor I think I have the wiring right but I'm getting a huge voltage drop through the transistor. Right now I'm just trying to bread board a simple circuit to turn on a LED but I'm going from 7.6 volts through the switch to 1.6 after the transistor! When I press the button I get a short flash from the LED and then nothing.

I set up a darlington pair using another TIP31 with two exposed wires as the touch switch. With the two transistors I'm getting 2.1 volts at the LED. There are no resistors on the board anywhere.

My basic circuit is:

Positive --> LED --> Collector
Positive --> Switch --> Base
Emitter --> Ground

I tried putting a 10K resistor on the base but then I didn't even get enough current to make the LED flash.

I keep reading data sheets and looking at transistor tutorials, mine seems like it should work but it simply isn't!

 

[UberSquid]

power supply on my breadboard was fried. Never mind.