Adding Potentiometer to Fan (consumer product)

Thread Starter

stiener

Joined Dec 11, 2022
12
Hello, I have a sleeping sound machine that uses a Fan to create white noise. It has a 3 position Switch, "off", "high speed", and "low speed". Essentially, these settings are either too loud or too quiet.

I would like to remove the 3 setting Switch and replace it with a Potentiometer to cleany sweep through the values.

My questions are, where to solder the potetiometer in? Also, what potentiometer to get?
Bonus would to have it sweep to an "off" positition.
I have a bunch of 10K radial pots for Arduino stuff. I am somewhat electronically inclined, but not tremendous with this stuff. I wanted to be sure to ask someone before cutting wires on a purchased product. =)
Sheet copy.jpg
Thank you!
 

djsfantasi

Joined Apr 11, 2010
9,160
One would think that a potentiometer to sweep through a continuum of resistance values would be an appropriate solution - if the fan were controlled by a resistance.

However, fan speeds are usually controlled by separate coils in the fan motor. There is a low speed coil and a medium speed coil. High speed is created by powering both coils. This is consistent with your drawing of how the fan is wired
So no continuum of “resistance” can be used to control the fan speed. The speed control switch is exactly that. A “switch”.

It might be possible to control the fan speed by other means. But you’d need to supply more information about the motor.
 

Thread Starter

stiener

Joined Dec 11, 2022
12
Ahh, I see. That makes total sense... Drat!
I couldn't find the data sheet on the motor, then again I am not great at that search. It is a Yogasleep (Marpac) Dohm Classic.
Here are some pictures, but I realized this information might not be enough to safely modify the fan.
However, thank you for your reply. If we knew more about the motor, what did you have in mind? A mosfet, or maybe a 10 position switch, maybe mcu controlled...? Or impossible?
Sheet2 copy.jpg
 

djsfantasi

Joined Apr 11, 2010
9,160
My idea is actually outside my pay grade. I know that some types of motors can be controlled by a household dimmer switch. Or perhaps you can find a motor controller specifically for changing speed. When reducing a motor’s speed, there are several possible problems. The reduced torque with the load of the fan blades can overheat the motor. Thus there is a minimum speed. Also, some of the techniques used in a dimmer will also overheat the motor.

So while I wouldn’t say it’s impossible, it is surely more difficult than a couple of discrete components.

Maybe someone more familiar with motor speed control will chime in.
 

LowQCab

Joined Nov 6, 2012
4,063
That's a standard "Shaded-Pole" Motor.
It can be slowed-down overall with just a BIG-Resistor,
the chosen Resistor may produce ~10 to ~20-Watts of HEAT.
The fan can keep it reasonably cool.

The Motor doesn't have a Current or Wattage-Rating on the tag so you'll have to guess at it.
I would guess that You will need maybe a ~1-Ohm, 10-Watt, Resistor,
but to make sure that You will have a combination that will do what You want,
You should also buy a 2-Ohm, a 4-Ohm, and a 10-Ohm, Resistors.
You can experiment with placing the Resistors in Series or Parallel to achieve different values.

The Speed-Selector-Switch will still work as normal,
but all speeds will be reduced to some degree.

But, I wouldn't recommend going this route for such a simple problem.
Just place the Fan further away from You, or partially cover it with a Folded-Towel.
Do not completely block-off Cooling Air to the Fan-Motor.

For sleep problems,
1) Stop watching TV.
2) Stop taking Prescription-Drugs, completely.
3) Cut-Out -- Sugar, High-Fructose-Corn-Syrup, Caffeine, and Alcohol, completely.
4) Start taking Vitamins and Minerals, everyday.
5) Learn to control your thoughts,
( this also reduces Stress ), ( learn to think about what You WANT to think about ).
6) Go to Sleep "on-purpose", and on a schedule, and before You are completely exhausted.

Once You figure all this out,
( which will take some considerable time and effort ),
You will be able to fall to sleep in less than a Minute,
even in a noisy environment,
and wake-up feeling sharp and ready to go.

There's no "easy" solution, and no "Pill" You can take.
.
.
.
 

Thread Starter

stiener

Joined Dec 11, 2022
12
Rats! I see what you mean with the resistors, and also what djsfantasi meant by using a more complex control. Seems like too much of a hassle and possibly might burn the house down whilst sleeping. heh At least I know the motor type (shaded pole, thanks LowQCab). ..I might just 3d print a housing to envelop the machine, leaving holes for airflow and cooling.

Also, I appreciate the sleep tips. I got a few down, and a few to work on. I place this sound machine between the window and my head to silence morning birds.
 

DickCappels

Joined Aug 21, 2008
10,169
Using resistors might work but I suspect you would have to use big resistors. I tried a triac lamp dimmer but then fan emitted a buzzing sound (it "kicked" the motor every half cycle) which defeated the whole point of slowing down the fan. Then I tried a Variac (variable auto transformer) and it worked great but they are expensive and very large and heavy.

The solution I found that gives pleasing results was to put a motor run capacitor in series with the fan motor. Now I have two floor fans that gently move the air but I cannot hear. I had to experiment, putting capacitors in parallel to determine how much capacitance I needed for the particular model of fan that I had.
 

Sensacell

Joined Jun 19, 2012
3,442
A Variac (AC variable auto-transformer) would allow you to adjust the input voltage to slow it down.
Since its a shaded-pole motor, the range of variation will be small and rather unpredictable, since these motors are generally not used for variable speed applications.

Once you found the happy speed, you might be able to use a fixed transformer to buck the AC voltage down as a permanent solution.
 

strantor

Joined Oct 3, 2010
6,789
Shaded pole motors are about 25% efficient. Running current and stall current are close to the same. I've been told that a shaded pole motor can be stalled out indefinitely without burning up, and that's why they're used for microwave turntables. How often do those get stalled?

I would think you could slow it down by jamming a stick against the shaft or something. But this is for informational purposes only and I take no responsibility for anyone's house burning down.
 

Audioguru again

Joined Oct 21, 2019
6,688
I have no problem with sleeping and have no noises keeping me from sleeping or suddenly waking me.
I am 77 years old and my medications are keeping me alive, not affecting my sleep.

I think most anti-vaxers and a certain religion say "stop taking your medications". I got my 5th dose (the second booster) of Covid19 and Flu over one month ago, they are also keeping me alive. A friend takes "sleeping pills" that cause many problems.

Hey just thinking, I don't wear my hearing aids when I sleep so my hearing loss blocks sounds that might keep me from sleeping.
Also my worn out hearing has tinnitus that produces continuous high frequencies white noise that covers-up any noises that might keep me from sleeping.
 

DickCappels

Joined Aug 21, 2008
10,169
This thread is not about our ideas about vaccine. I am glad that you are well and hope you continue to be well. Not wearing your hearing aids sounds like a very good idea. Hey! Give me a few year....I am trying to catch up with you!!
 

Audioguru again

Joined Oct 21, 2019
6,688
An electric fan Is used to make white noise? If it helps you sleep then why not make or use an electronic noise maker circuit driving a speaker? Of course it will have a variable volume control.
 

Thread Starter

stiener

Joined Dec 11, 2022
12
I have tried speakers. The smaller the speaker, the lower quality the sound is, especially white noise. Without some type of bass, it sounds so bright and tinny, like static, not white noise. The fan provides a more true sound, and this particular one allows you to rotate two parts of it to "sculpt" the sound. Kinda like a low/high pass on the high and low frequencies. This was essential. It is just kinda too loud
I like Sensacell's idea of bucking the AC voltage. I dont want excess heat to be a factor coming from large resistors.
I love the Audioguru again's idea of just being part deaf and taking your hearing aids out at night! No problems whatsoever hehehe Good times. Of course as strantor said, I can always just jam a stick in it! =)
I also have tinnitus so the sound machine helps a lot
 

djsfantasi

Joined Apr 11, 2010
9,160
Have you ever had a sleep test? Immediately after reading your post. I wondered. I fought insomnia for decades. Chamomile tea, hot milk, melatonin, a litany of sleep meds, white noise, brown noise, meditation… I must have tried everything.

This past spring, I was prescribed a sleep test by my doctor. They’re quite simple nowadays and can be done one night at home. I then was diagnosed with sleep apnea. I stopped breathing every five minutes! And anxiety of not being able to sleep only made it worse.

I just got a CPAP machine; I don’t need a full face mask, just a small nose pillow. There was a backlog, so I had to wait six months for it. I used to take two hours and three cups of coffee in the morning before I felt functional. The first night on the machine, I slept through the night and woke fully refreshed and alert. And my insurance paid for it all.

Maybe you can find my story useful.
 

Audioguru again

Joined Oct 21, 2019
6,688
Lookup pink noise in Google.
White noise sounds very harsh. Pink noise sounds smooth.
Pink noise has higher frequency levels dropping as the frequencies rise. Pink noise has equal power in each octave of frequencies. I used pink noise for testing and setting-up theater sound systems so that all frequencies sound to be at the same level.
Some half-decent and inexpensive 4" and 5" diameter speakers produce a wide range of frequencies including bass.
A fairly simple white noise generator can be built and a simple filter smooths the white noise into pink noise.

In the last 5 years, doctors have discovered that pink noise causes quicker and deeper sleep than white noise and the deeper sleep improves human memory.

Guess what. My poor hearing with my hearing aids off causes me to not hear a smoke detector. Then my dog wakes me.
 

Thread Starter

stiener

Joined Dec 11, 2022
12
TBH my sleep problems stem from tinnitus. It is such a unique slice of insanity, such that it obliterates your quiet moments. Closing your eyes makes it worse. Its year 5 now, so Ive learned to ignore it.

If anything can be found in my story... your hearing is absolutely precious, and should be protected at all cost. Nothing at all in this world is worth getting tinnitus over.
 

Thread Starter

stiener

Joined Dec 11, 2022
12
Thats actually pretty clever. I could hop into Ableton and shape it a bit. My computer speakers are pretty small but thats a good idea.
 
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