SFRemover!

[Hydrostat]

jolly good day!

ive started my very first project and decided making a SFR or solder-fume-remover 
using 2x9v batteries + a 12V fan, which already has a switch for high/med/low!

since some simple cables and a resistor would be way too easy, i decided adding 2 LEDs:
one as a main power LED and the second to roughly indicate the fan speed ie. high=bright, med=less-bright, low=off

the circuit:
- theres 2x9V batteries in series, obviously DC, with a rough 1Ohm resistance
- connected to 3 parallels
first with a 1kOhm resistor, followed by a 1.9V/25mA LED (main)
second, is a valve with a 50kOhm low profile pot (just in case the fan might have to be replaced)
and third comes the 12V fan, which ranges from 130mA to 550mA
- now the final status LED (2V/10mA), is not connected in parallel with the circuit
after the fan, the LED arcs over a 6Ohm resistor (3x2Ohm actually...)

finally, the question/s!
am i doing any thing horribly wrong and/or could i optimize it?

clearly i could also slap a touch-screen on there, but lets stay analog 

cheers!

[Hydrostat]

precisely, the valve regulates the the voltage, allowing individual components to fail (ie LEDs) without affecting the rest too much - obviously also depends on the fail

im not quite sure if im interpreting your circuit correctly, your using a transistor and mosfet to regulate the voltage?
so you always get a constant 16V no matter how depleated or overcharged the batteries are
or are there other advantages over mine?

ps: what software are you using there? 

[ovnr]

Er... valve?


If you're not overly attached to your three-stage switch, just stick a BJT transistor and a potentiometer (and a couple resistors) on there, and twiddle the pot to set the value. Search for "fan controller circuit" or similar.


Or just buy a finished product for less than two dollars, delivered.

[Hydrostat]

buying something already made wouldnt teach me much though 

and yep, its clear that the "valve" pot should never go to 0, its currently set to max and since i only have one screwdriver that can actually turn it, its not such a hazard, after all this pot isnt intended to control the fan speed (the fan already has a switch) - also been thinking of just replacing it with a simple resistor or add one to keep a minimum value, but why keep fiddling around with it, if the concept isnt good?

im not at all attached to the initial concept, but i also dont want to simply copy something and eventually only understand half of it
ie. even if i know what a NPN does by its self, it doesnt necessarily mean i fully understand its role and benefits in the given circuit

sofar Q1 is a NPN, thats clear, yet im still struggling to understand what R2 is
hope its not just a pot with earth connection

[Hydrostat]

i know im bad at giving examples 
but i know all the theory about ohms law up until orbital mechanics (also went through all of daves and mjlortons beginner vids, at least once), but what use is a smartphone if you have no fingers?... 
ie. ive watched 20+vids about capacitors, but still dont know how to appropriately implement them

the ohms law clip you posted for example, it shows resistors in series, in parallel and mixed (where the series-resistor is before the parallel lines)
BUT! how would i apply that to the 6Ohm resistor/s in my initial circuit? and what if (theoretically) there would be another resistor in front of the 2nd LED?
clearly, the 6Ohmer can be considered in series to the circuit, but its parallel to the LED?...
so eventually id also need to know the LEDs effect on the rest of the circuit etc

also, and thats probably been the problem all along - i cannot tell the difference, because i STILL dont fully understand what R2 is 
now WHAT is R2?... a nuclear fusion reactor? a fly squatting cruise missile launcher? 
its clear that it somehow regulates the NPNs base, but how and what for? i doubt that its going to be magic 
obviously i could just assume it does, what the NPN theoretically needs, but how do i know it only does that if i dont know what it is...

yes we all have to start somewhere, but it also helps not going in circles too many times 

ps: no worries, even if your going to tell me that i need pythagoras, ill look at it constructively 
also i might be asking a little "dumb", but thats just to prevent missing things that might be completely obvious to you - ie. assuming your programming an AI, you teach it all about humans and what they drink etc.
now it sees that 80% of the people drinking diet-coke are fat, it would assume that they are fat because of the diet-coke - while we would think its totally obvious that they drink it, because they have too much weight 

[Hydrostat]

yeey getting somewhere! the third connection confused me

now for full understanding, if i wouldnt want an additional option to regulate the voltage, i wouldnt need the transistor right?
and in the case id leave the pot in there, its simply more elegant than using a pot+resistor in parallel?
or are there other advantages, apart from not being able to pass the full charge through the pot, like heat dissipation?
clearly theres almost always multiple ways to an answer, but knowing why something is better than something else, also helps preventing odd designs 

ps: welcome to the sleepless club 

[Hydrostat]

so the transistor makes a series out of a parallel
and generally its better to prevent parallels as much as possible?

looking back at your Untitled-4.jpg, should the fan brake/burn/rust or similar, wouldnt that burn the LED at the same time?

cheers for your help! 

[djacobow]

Why would someone want to remove solder fumes? That's the best part!

<ducks>

[Hydrostat]

ok, lets pretend my neighbor also wants to smell some of it and this "ingenious" device ensures he also receives a decent breeze