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ajriding

st clair

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Posted: 08/24/21 06:04pm Link  |  Quote  |  Print  |  Notify Moderator

Im looking for a fan speed control.
Please dont post your internet search results here. Anyone, including me, can do a search and find mindless stuff. I am looking for specific knowledge, thanks

The Fantastic fan has 3 speed. High, but the Low and Med are regulated with a heating element, so running low save no electricity, and might even use more.

I would like to wire in a speed control that uses less energy at lower speeds (that doesn't just burn off electricity in the form of heat to reduce current to the fan).

I have a PWM controller that worked fine. I let it run all night on a low setting with no issues, and today I left it on a few hours on a higher speed (less than full though), and went back to find it burned out, and hot. The default setting if something happens is to just put out full power, so the fan was running on high.
When it worked it makes a ringing sound at the fan.
I cannot find the exact match, but it was similar to this one on eBay, same case at least.

IDK why it burned out, it is rated at 8 amps, and the FF is about 2.

So, Im trying to figure out what controller will do what I want.

I have another controller, but it has a really big heat sink, so I assume it will waste power making a lot of heat.

* This post was edited 08/24/21 06:15pm by ajriding *

QCMan

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Posted: 08/24/21 07:24pm Link  |  Quote  |  Print  |  Notify Moderator

You will find that just about every fan speed control uses resistors, not heating elements as you suggest. Unless the fan is using an integrated digital controller it will use resistors. If you don't like resistor circuits you should look for a digitally controlled fan that fits in the housing you have. I have found some on an internet search but you do not want links so you can do a search on your own. Be aware, to "save" a tiny amount of power you will pay dearly. Good luck.


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ajriding

st clair

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Posted: 08/24/21 09:11pm Link  |  Quote  |  Print  |  Notify Moderator

The Fantastic fan used to use a literal heating element I call it, which looks like a coil spring element you would see on an electric heater. The Low setting uses two springs.
Im not looking for that or any resistor device that just waste electricity.
If you have actual knowledge and a link that is fine, but amazing how many people read a post, know nothing at all about the topic, spend 3 seconds on a search and post as if they are now experts, and think that is all that is to it, still knowing nothing at all about the topic. Nobody is interested in that.

Tiny amounts of electricity are what camper batteries have, so yes, I am worried about tiny amounts of electricity.

TurnThePage

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Posted: 08/24/21 10:05pm Link  |  Quote  |  Print  |  Notify Moderator

You may have had a bad PWM. I added one to my bathroom fan (the cheap one that
many here use, but I can't remember the name of) years ago, and it's still going strong, and quiet. Sorry I can't remember much about it beyond that.

I did just add a 2 amp fan to my bed area, and connected it to a PWM controller that seems to be working well so far. It's very over rated for the job though. And annoyingly it doesn't shut completely off, so I need to add a power switch too. Beyond that it's working great so far.

https://www.amazon.com/gp/product/B071NQ........_yo_dt_b_search_asin_title?ie=UTF8&psc=1


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2112

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Posted: 08/25/21 04:52am Link  |  Quote  |  Print  |  Notify Moderator

I know I'm not suppose to post mindless internet search results but This Guide is an excellent source of information. It directs you to the proper controller, how to bypass the coil wire wound resistors and a clean way to install the controller. All your questions are answered here.


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ajriding

st clair

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Posted: 08/25/21 02:16pm Link  |  Quote  |  Print  |  Notify Moderator

mindless is when people just look up "speed controller" and post a bunch of links, none that are relevant usually.

That Guide to put a controller in is nice, but not anything to do with what I want - to have a controller that uses less energy at lower speeds.
I have my controller feeding the FF, so have control on a wall, not at the fan. I can always put controller at max and run the FF normally. I set FF on High and control the speed by using the controller.

The PWM things have big heat sinks, so are producing heat. IDK beyond that, so am asking any electrical geeks out there who might know

DrewE

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Posted: 08/25/21 03:29pm Link  |  Quote  |  Print  |  Notify Moderator

A PWM circuit will use less power at lower speeds.

The original resistor will, as well, but is not as efficient as the PWM units. (Adding the resistance into the circuit decreases the current, per Ohm's law, which means less power consumed.) Ideally the switching devices in a PWM circuit will dissipate no power, since they are either fully on or fully off with no time spent in between where they act as a resistive divider with the load. For practical circuits, that's not quite achievable since semiconductor switching times are not truly instantaneous and since the on state has a bit of impedance, but it gets quite close.

The unit you had that failed was most likely some sort of a PWM controller. It may well have failed due to the lack of a big enough heat sink, allowing the switching transistor to overheat.





ajriding

st clair

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Posted: 08/25/21 04:12pm Link  |  Quote  |  Print  |  Notify Moderator

Hmm, ok. I guess how hot the coil resistor in the FF gets determines how much waste there is. IDK.

The PWM I have has no holes for ventilation to move the heat out.
What happens when battery power is too low to move the fan and the PWM is sending out power still? Harm to fan? Harm to controller?

I guess I will just get a PWM but one with vent holes this time.

theoldwizard1

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Posted: 08/25/21 05:13pm Link  |  Quote  |  Print  |  Notify Moderator

QCMan wrote:

You will find that just about every fan speed control uses resistors, ...

What the OP wants is a pulse width modulated (PWM) speed control. It is the most "optimal". Very little energy is wasted (turned into heat).

2112

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Posted: 08/25/21 07:16pm Link  |  Quote  |  Print  |  Notify Moderator

Quote:

What happens when battery power is too low to move the fan and the PWM is sending out power still? Harm to fan? Harm to controller?
That could be a problem. A quality controller would use a low voltage dropout regulator to protect itself from this. The one you pointed to can regulate down to 10 volts. It could heat up below that. You will have some line loss depending on what wire you use. A battery voltage below 11.5V (just my guess) might create 10V at the controller.

Why not try the one you pointed to on eBay? It's $13 delivered. 25KHz switching frequency so it shouldn't be noisy, rated for 10A and has a power switch. I assume you already have the wires located where you want it on the wall. Did you run 16awg wire? Wires being too small/long could be a problem.

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