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Experiences with a solder fume fan for my bench.

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DrG

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I like to use a fan when I solder. Some people think that is silly and I don't care much to argue the point. No over-reaction, no paranoia, none of that. I just figure the less of those fumes that I inhale and the less of those fumes that get into my eyes, the better. I am not suggesting an expensive filtered fume extractor is mandatory although I would probably use one if it were given to me.

What I normally used to use in the past was an AC fan that you would likely call an office or desk fan - maybe 12-14" in diameter. Rather bulky for a bench, but it was effective in mitigating concentrated fumes. So, I had it in my head to build a small fan that could be brought out just for soldering.

I have some familiarity with PIC chips and PWM and an 1840 seemed like a reasonable choice.

Here is the schematic that I came up with, simple as it is. Five switches control the fan - off, 25%, 50%, 75% and 100%.
119619


Then the asm code (see attached) and the bread-board circuit
119621


The fan that I used is *very* small, and very cheap, but actually performs well.

119622


The circuit and program work great! No whine, no stalling at 25%, it performs as well as I hoped that it would. Just a couple of notes...C2 is mandatory and a larger value might be needed for another fan. I did not use a serial resistor on the gate of the mosfet - I saw no difference if I added one. I still struggle a bit with determining when one is necessary. R6 is a habit with me, I like things pulled down if the thing could be floating. Also, there is a lot to using PWM with fans - read about that if you are interested.

On the code - it's pretty straightforward. I am using a 10K duty cycle (if I calculated correctly). There is a trade-off between PWM resolution and PWM duty cycle as I recall - so don't think that you can get ultrasonic frequencies with 10 bit resolution. Anyways, I am sure there are plenty of people on here who know much more about the details and there is much information on the subject available online (some of it quite good and some of it just plain wrong). While the data sheet can be cumbersome, especially if you are not familiar with Microchip, all the info is actually in there.

OK, so now, it is time to take it off the breadboard and into an enclosure so that the project can be used conveniently. That is the part that I hate because I am not too good with those skills (I am being kind). Often times, working circuits will simply stay on the breadboard. For me, the fun is in designing and coding something that works, not packaging.

So, it sits on the breadboard for a few months....and a few more months...makes its way onto a list of things to do and so on and so forth.

Then, I come across this in a brick and mortar store - can't remember exactly, but I think it was maybe $8.

119625


Has a built-in rechargeable battery. Can be charged from a USB port or charger. Runs while charging and works fine off of a 5V power bank when I have forgotten to charge it. Runs for a couple of hours on a full charge. Plenty effective for directing the fumes away from me while soldering. It is small enough (5.5" X 4") to easily position while soldering. Three speeds and the highest is effective even at a distance that is far enough to be well out of the way.

I simply can't do better than that.

So, at the end of the day, the circuit gets taken off the bread board. The components go into a labelled bag along with the printed schematic and a note about the programming. No time was wasted. I learned a lot and have increased my arsenal, so-to-speak.

PS: with regard to the code and schematic...I am fine with comments and even criticisms. In fact, if you see something that is just plain wrong, please do let me know so that I will learn. If you see something that could be improved, I welcome the discussion if it also contains some clear explanation of why it is an improvement. If you are wondering why I did something in the way that I did, the answer is usually..because that is the way that works :)
 

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  • 1840switchPWM.asm
    7.1 KB · Views: 124
Just a couple of notes...C2 is mandatory and a larger value might be needed for another fan. I did not use a serial resistor on the gate of the mosfet - I saw no difference if I added one. I still struggle a bit with determining when one is necessary. R6 is a habit with me, I like things pulled down if the thing could be floating.

I'm a bit dubious about the need for C2?, never mind 'mandatory', and 100uF already seems massively excessive?. If the fan perhaps one that can't be PWM'd?

However, R6, no problem - that SHOULD be mandatory :D

Just ordered some boards from China, on which I'm using 2N7000 FET's - I obviously added 'R6' (but 1M), and added a series resistor (10K) - like you, don't know if it was needed or not, but it won't do any harm , and could easily be replaced by a 'bit of wire'.
 
I use a fume extractor as well. Saves me some headaches once in awhile.

I have this one. Its really cheap. Works ok long as its close. Your fan honestly probably works better.
Smoke_Exrtractor_56b9904f-03de-4e44-9a78-5f62f8ed6bdc_1024x1024.jpg


What works best for me tho is the extractor that is on the end of my soldering iron. My main station has it built in like below but I have been meaning to make another one for my secondary station just never get around to it. Its pretty simple to do and maybe you could make a fun project out of it.
iron_6.jpg
 
I use a fume extractor as well. Saves me some headaches once in awhile.

I have this one. Its really cheap. Works ok long as its close. Your fan honestly probably works better.
View attachment 119631

What works best for me tho is the extractor that is on the end of my soldering iron. My main station has it built in like below but I have been meaning to make another one for my secondary station just never get around to it. Its pretty simple to do and maybe you could make a fun project out of it.
View attachment 119632
Have you ever actually tried to make a tip extractor? I found it much more difficult since I can't seem to source any reasonably sized fans/pumps that can produce enough static pressure. I have found there are more than just solder fumes that bug me too...the flux solvent and cleaning vapours get to me and tip extraction doesn't work for those.
 
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Mostly its the flux fumes that get me and these tip extractors work very well for it. Biggest issue is you need to keep it close to tip and you need to regularly clean the nozzle from the build up inside.

I have not tried to make one no. I have seen a few different styles done and it does not look hard to do.
 
I've mentioned it before, but I'll mention it again!.

I was once part of a study by the Health & Safety Executive, which was researching the possible requirement of fume extraction in a service environment.

I asked what the possible hazards actually were, and it WASN'T the solder (leaded or not), it was the flux - apparently the fumes from the flux 'can' trigger asthma attacks in asthma sufferers. However, as part of this study (as well as fitting me with a monitor while I worked) they did a large survey of the UK electronics service industry - and were unable to find a single asthma sufferer. They concluded that either:

a) People with asthma don't become service engineers?.
b) Those who did, left because it triggered attacks?.

The results of the practical measurements (on me and others) were that there's no need for fume extraction in a service environment, only in a manufacturing one.
 
For me basic soldering fumes generally do not bother me this is true, but sometimes I am leaning over and into modules all day long for repairs and rework. Heavy flux creates a lot of fumes and there are other things like potting material/conformal coatings left over even after vigorous cleaning. Toxic or not, all of this tends to get in the way of breathing in oxygen... While I'm sure your study was accurate in some environments I doubt it holds much weight to individuals. I am going to stick to the opinion that if someone feels they need some type of ventilation than they probably do . I don't suffer from asthma so I can not comment on that, but it is an easy trigger for migraines that's for sure.

Leaning back for fresh air or taking breaks every once in awhile is much more effective then extractors but only you guys who get salary's or paid hourly have time for that.
 
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I'm a bit dubious about the need for C2?, never mind 'mandatory', and 100uF already seems massively excessive?. If the fan perhaps one that can't be PWM'd?

However, R6, no problem - that SHOULD be mandatory :D

Just ordered some boards from China, on which I'm using 2N7000 FET's - I obviously added 'R6' (but 1M), and added a series resistor (10K) - like you, don't know if it was needed or not, but it won't do any harm , and could easily be replaced by a 'bit of wire'.

You raise some good points and I am very open to discussing and learning more.

I chose the word "mandatory" in a deliberate fashion. In my example, on my bench, without C2, the fan will not turn below 100% duty cycle. Additionally, a small capacitor (say 10 uF, for example) would not change that outcome.

Using a larger fan (also 5v, specs here), it would turn at different duty cycles, but always with a distinctive whine. Adding a 220 uf capacitor, greatly reduced that hum, but did not completely removed it. Lower values were proportionally less effective. I looked into raising the duty cycle but, as I said, there are limits there and trade-offs with resolution. I agree with your "massively excessive" evaluation - it seemed that way to me as well

This is empirical for me. I do not know enough about motors and I am ok with admitting that but it does not mean I am comfortable with that.

I wish I had saved all of the reference and links that I went through with just this issue, but I have not.

Here are some that I easily brought back to memory:


There was a stackexchange thread where some one explained why a high value capacitor would work and I can't find it but I know I read it as it what led me to start trying "big caps"

I also note this "If the fan perhaps one that can't be PWM'd?" I came accross this language also. We all know that there are many examples of 12V PC fans that can/do use PWM. Further, if adding the cap (as in my case) makes PWM work, does it mean it can be PWM'd or does it mean using one will accelerate motor failure? I don't know, I would like to know, but I don't clearly understand.
 
Presumably adding the capacitor works as some kind of crude filter, so giving 'more' of a DC level across the motor?.

But it's rather crude and nasty, as is obvious the FET is shorting the capacitor to ground every time it turns ON.

Have you tried the capacitor directly across the motor? - I'd be much happier with that scenario, and it should be much more effective.
 
Have you tried the capacitor directly across the motor? - I'd be much happier with that scenario, and it should be much more effective.

I have and I see no difference at all.

To be clear, a 4.7uf will "work" but will not start the fan at lower duty cycles. If you start at 100%, the fan will then continue to run at lower duty cycles. A 100 uf cap will start and run the fan at all of the switch-selectable. Changing the position from what you see in the schematic and picture to across the fan leads makes no difference.

EDIT: This is the thread that I read to try a large cap.
 
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Just a total guess here. Is it possable that your desired fan speed, from the PWM output, is to low to overcome the starting(stalled motor) current? Since your using a micro to generate the PWM, couldn't you program a "ramp down from full PWM" in to it?
 
Just a total guess here. Is it possable that your desired fan speed, from the PWM output, is to low to overcome the starting(stalled motor) current? Since your using a micro to generate the PWM, couldn't you program a "ramp down from full PWM" in to it?

Yeah, well it sure sounds that way to me - not getting to the starting current. To summarize:
With El cheapo motor in the pic:

No cap, only works at 100% duty cycle. Starting at 100% and going lower (75,50,25) will stall. Will not start at 75,50,25.

Adding a 4.7u cap (cheap electrolytic) Will start at 100, but not below. If started at 100, will continue at lower.

Adding a 100 uf cap, will start at all duty cycles (sometimes takes a sec or so at 25) and will readily go back and forth without stalls.

Not a whole lot of hum or vibration as long as it is not stalled.
_____

Using the second fan (I linked the specs in #8) there is no stalling without the cap, but there is hum or whine at < 100% (and the pitch changes slightly at different duty cycles). A 200uf (or was it 220?) almost completely removes the hum. Using a 100uf reduces the hum, but not as much.

I may try lowering the PWM period to 100Hz with that one.

Thing is, for soldering, I have solved the issue with the little commercial fan so I want to pack it and stash it...still, I would like to know more. There is always more to this stuff...it never stops, you people with the motors...you start them and you stop them...what's the problem? :):):)
 
a) People with asthma don't become service engineers?.
b) Those who did, left because it triggered attacks?.
People that died from lung cancer do not complain about work conditions.
Just lost another friend from lung cancer related to work. 1)asbestos 2)paint fumes (lacer)
 
People that died from lung cancer do not complain about work conditions.
Just lost another friend from lung cancer related to work. 1)asbestos 2)paint fumes (lacer)

Lung cancer is not the life sentence it used to be.

Two years ago, my partner went to the emergency room after eating some bad sushi. That turned out to be nothing serious, but the CT of his stomach revealed a nodule in his lung. He was 42 years old, had never smoked and had no known risk factors. A great many tests were done, attempting to rule out cancer, but eventually the conclusion was the nodule was cancer.

The nodule and half of his lung were removed a year ago last December using minimally invasive robotic surgery. All the lymph nodes were clear and the tumor was removed with clean. He was in the hospital about 3 days, and after he left the hospital, the strongest medication he took was Tylenol. As of today, there has be no recurrence of the cancer.

Caught early, lung cancer is not a death sentence. The problem is that by the time there are external symptoms, the cancer is far advanced. Research has shown that more and more relatively young people with no known risk factors are being discovered with lung cancer and early treatment saves lifes.

But treatments are coming online now that are very promising at stopping or at least substantially slowing even advanced lung cancers. A friend of ours who has stage 4 lung cancer has recently enrolled in a Phase 2 drug trial (meaning it's being tested for effectiveness) that has shown it's possible to stop cancers with certain mutations.

There is hope on the cancer front.
 
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