Slowing down a FantasticVent

[wannabefree]

Tony, I suspect the difference in measured current between your fan and mine is more likely due to power loss in your wiring. The test for that is to measure the voltage at your fan vs. the voltage at your battery. A 1V difference is significant.
Here at WBF labs I cobbled together a controller based on a 555 timer with a FET buffer. I got the boards back from fab Tuesday, built one up last night and hooked it up to my FF tonight. Unfortunately, I did not think to do some sound level measurements on the fan in its original configuration, so all I can say sound-wise is it sounds about the same to me with the PWM control as with the original switch at comparable settings. Sounds like a fan. No weird noises added to what was already there.
I just clip leaded it to a 12V socket in the tear and was dropping a full volt over the 36 inches of lead wire, slowing the fan a bit from when it is installed properly (fed by 14 gauge wire, not 20 gauge clip leads) and dropping my max current from 3.12A to 2.4A. Some of the drop is due to the controller which goes to about 98% duty cycle, not 100% like you would get with the switch, but I would expect a 2% difference from that, not 23% or so as seen.
Anyway, I am getting very long winded to say that, as I suspected, the noise people are hearing is due to using a PWM control that operates in the audio range, not some weirdness due to the fan not liking PWM.
If anyone is interested I can post the schematic.

[tony.latham]

Tony, I suspect the difference in measured current between your fan and mine is more likely due to power loss in your wiring.

The run from the fuse box to the fan is about 6' of copper-stranded 14 AWG. From the battery to the fuse box it's 12 AWG for 10'.

Tony

[wannabefree]

OK, you win. Must be the meter. Or my meter. Cheers!

[tony.latham]

OK, you win. Must be the meter. Or my meter. Cheers!

Wanna:

Hey, you're talking to a guy that has a DC IQ of about .... 76?

It could very well be my $19 meter. Eight-bits says yours is a lot more accurate.



I appreciate your thoughts on the matter.

Tony

[wannabefree]

Gads! I can't believe it. We are using exactly the same thing . For 10 years I used a homebrew coulomb counter that was a great idea, but flawed execution. If you are into the electronics stuff, low side sensing without a negative power supply is a real challenge I had seriously underestimated. Then I saw this thing and bought one. Installed it about a month ago and tested it at that time and it was within 5% on volts and 10% on amps of my good meter (not a Fluke but not exactly cheap, either).

[tony.latham]

Gads! I can't believe it.

Glad to see you compared it to a Fluke.

Tony

[rbtrary]

What do you guys think of this write up?

Variable Speed PWM Fantastic Fan Mod for10 Bucks?

https://tab-rv.vanillacommunity.com/dis ... MVg#latest

[Graniterich]

I tried one, caused the fan to whine, a heard some do and some don't!

[wannabefree]

Sadly, making the FF variable speed with PWM is neither simple nor cheap. The reason why so many of these PWM devices make the fan whine is that they are running in the audio range, most of them between 200 and 2500 Hz. So if you buy one, make sure you get one that operates above 20 kHz.
Next, you lose the reverse feature or the power switch -- choose one -- because these electronic things do not like to have their input voltage reversed. So, you can install your PWM with the reverse switch on the output of the PWM, but then you can't turn off power to the PWM so it is sucking down the battery full-time, or you can install yet another power switch in your fan so you can switch off the PWM and still have reverse. As I have taken the time to play with some PWMs myself, even built one from scratch, I am finding them all (even the one I built) unsatisfactory solutions because finding the efficiency I thought was so obvious is not so easy at 12V when losses in some of these devices can be on the order of 3V. So far, a 4 or 8 ohm resistor in the airflow from the fan, as suggested by the Fantastic People at Fantastic Fan is the best, simplest solution.
Not that I am giving up, mind you. My next version, for which I ordered PCBs yesterday, will be reversible, but will also be inefficient. If it slows the fan and burns less watts than the resistors, even by a small margin, I will live with it. As I said, I expect to be disappointed, but stay tuned as I will report what I learn. This is what retired engineers do, I guess. I just can't give it up. Still figuring out this retirement thing

[rbtrary]

what about this controller?

https://www.amazon.com/gp/product/B007T ... UTF8&psc=1

[wannabefree]

Who knows? They did not publish the operating frequency, which you need to know if you don't want to hear the fan squeal (no fair pulling out the hearing aids - enlist a helper who can still hear). For $11, why not try one and post your experience?
One note on reverse polarity protection - that means 1 of 2 things:
1 - a series blocking diode with a 0.7V loss, hook it up backwards and it won't work, but also doesn't free the magic smoke
2 - steering diodes which will lead to 1.4V dropped, but it will work no matter how you hook it up
Neither is fatal but the first can be inconvenient. If you put this after the reversing switch and they did #2, do not expect your fan to reverse, though it might. If you do get one, I would be interested in your results. In the meantime I will continue to tinker with my custom solution. It gives me something to think about
Note that this part looks very much like the part in the thread pointed to in rbtrary's post above. The referred to T@B post says nothing about reverse, which I am not willing to sacrifice and I suspect they did. I am a bit mystified by the 3 heatsinks on the board, too. One should suffice, even at 10A load (mine doesn't need any, why should theirs?). Makes me wonder what they are doing that generates all that heat.

[MJS613]

Hi All,

Great topic, I have set my Fantastic fan up with a PWM controller, it works great no humming or noise caused from the controller. I am having an issue and have a question that I am hoping you electrical gurus can answer for me. (You are a Guru cause you know more then me and I really know just enough to be dangerous.) So to give you a bit of a back story on my fan. When I got it we test fit it into the roof, tested it and it worked. The trailer then sat outside covered for a year before I could get back to it to get it to my new house. So when I got the trailer to my new house and in the shop, i tried the fan and it did not work. I pulled it out to find the 3 speed switch all rusted and corroded, so I decided to install a PWM so I could control the fan speed better. Went to test and was no go, so I went through the wiring and discovered the issue was a blown fuse in the fan. I replaced the fuse tested the fan all worked great, no issues was using a 18V drill battery for testing. Now come to yesterday when I was sorting out the electrical wiring in the trailer to get ready to put into the little fuse box I got, and the fan wouldn't work again. So I pulled it apart and discovered the fuse is blown again. (was testing with a 12v battery for the trailer this time). So my question is what might be making the fuse blow and secondly if I have the fan running from the fuse box with a 5 amp fuse do I still need the 4amp fuse in the fan? Now I know the fuse in the fan is a slow blow fuse, and the little fuse in the fuse panel I don't think would be a slow blow fuse. Any suggestions or advice would be amazing.

Thanks

[wannabefree]

The fuse is in the fan for those of us who put multiple items on one circuit. In this case, the 4A fuse in the fan will blow if the fan motor stalls (say a stick fell down into the fan blades) while the 20A fuse in the distribution box will not blow, leaving your all-important TV and 2000W stereo operating. So, if there is more than the fan on the circuit, I suggest you need the fuse. If not, maybe you don't need the fuse. The general rule is the fuse in the distro box should be sized appropriately for the wiring, while the fuse at the appliance is sized for the appliance.
Depending on the design of your speed controller, there may be periods during each on/off cycle that look like a short circuit to the fuse. This is particularly true if the controller incorporates an H-bridge and the designer wasn't careful to allow some dead time between cycles. That can be hard on fuses, not to mention battery life.
The mystery, as I see it, is that the fuse is blowing while the fan is not in use or immediately when you turn it on. This suggests a wiring error somewhere else in the former case and a poor PWM design in the latter. Perhaps the fuse is blowing while you are "sorting out wiring" and the problem will cease to exist as soon as that is all taken care of.
I could go on, but it will get way too techy. If you have a part number and source for your PWM, please PM me and I can look into it further. I got bored with this thread some time ago and nobody else seemed that interested, but I do have a couple solutions to the whole PWM issue, neither of which is totally satisfactory to me but you may revive my interest and maybe version 3, on the back burner long enough, may yet see the light of day.

[tony.latham]

Gads! I can't believe it. We are using exactly the same thing

Just a little update. I switched over from a Bayite to an AiLi meter and just tested the Fantastic fan draw again. I get the same .86 amps when it's on the #1 setting with it as I did the Bayite







The resistor slow-down does work.

Tony

[MJS613]

So I figured out the issue with the fuses, I had flipped the wiring so I hooked it up backwards, I have fixed the wiring, replaced the fuses and the new PWM board since i blew the one I had. All working great now will get to really test it out in 10 days !!