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DC fan to AC converter  Rate Topic 
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 Posted: Thu May 21st, 2020 02:39 am
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Anthony Lindsey
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What do you use to plug a DC fan into AC to run it?   I see converters but there are many options and I would like to be pointed in the right direction.     Not the wire in type just the plug  the outlet into type.

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 Posted: Thu May 21st, 2020 03:15 am
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Steve Stephens
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The easy, inexpensive, satisfactory way is to attache a "bridge rectifier" under the base of the fan or wire it into the power cord near the plug.   Here's a thread on bridge rectifiers.

http://www.afcaforum.com/forum1/42711.html

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 Posted: Thu May 21st, 2020 10:07 am
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Lane Shirey
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Steve Stephens wrote: The easy, inexpensive, satisfactory way is to attache a "bridge rectifier" under the base of the fan or wire it into the power cord near the plug.   Here's a thread on bridge rectifiers.

http://www.afcaforum.com/forum1/42711.html

Of course the bridge rectifier is the way to go if the fan is 100-120v . Otherwise you need a way to reduce the voltage by using a variac or other device along with the rectifier. Steve is spot on.  

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 Posted: Thu May 21st, 2020 11:40 am
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Bill Hoehn
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How about fuses?
Warren always used fuses when modifying DC fans for AC use.
How about it?

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 Posted: Thu May 21st, 2020 05:19 pm
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Sean Campbell
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So are the headwire soldered onto the + and - posts and the line cord soldered to the AC labeled posts? How is it secured inside the fan base? 

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 Posted: Thu May 21st, 2020 05:51 pm
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Anthony Lindsey
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I am still in the process of tearing this fan apart but once I get to putting it together I will revisit this.   Thanks for all the help.

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 Posted: Thu May 21st, 2020 06:20 pm
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Steve Stephens
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Sean Campbell wrote: How is it secured inside the fan base? I have seen the bridge rectifier secured inside the base using hot melt glue but polyurethane caulk would also work or other substances that would stick to the rectifier and base. 


Here is a bridge rectifier installed in base of 8" Colonial DC fan, Ron Jeter's



Last edited on Thu May 21st, 2020 06:23 pm by Steve Stephens

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 Posted: Fri May 22nd, 2020 01:36 am
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Steven P Dempsey
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This had an HP printer power supply - 30 volts or so


Attached Image (viewed 172 times):

1506 R&M.jpg

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 Posted: Fri May 22nd, 2020 05:22 pm
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Sean Campbell
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I wonder if affixing it with friction tape would work. It would detract less from the fan looking period accurate if flipped over.

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 Posted: Fri May 22nd, 2020 05:31 pm
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Steve Stephens
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Sean Campbell wrote: I wonder if affixing it with friction tape would work. It would detract less from the fan looking period accurate if flipped over.I think many fans, especially larger and later ones should have enough room under the base yet on top of the switch to completely hide the bridge rectifier.  

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 Posted: Sat May 23rd, 2020 03:39 pm
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Patrick Ray
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Those bridge rectifiers are nice and small and easy to hide. Just did a rewire on my Emerson 75048 and there was tons of room for it above the speed coil. Never even know it was up in there.




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 Posted: Sat May 23rd, 2020 06:21 pm
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William Dunlap
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A trap some folks fall into is not understanding that rectified 120VAC is actually more like 140VDC.
You could be overdriving your fan and causing damage. So, if your fans runs a lot faster on high speed, you should probably not run it there and just run it at the lower speeds.
You can also measure the VDC once rectified to prove this
Cheers,
Bill

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 Posted: Sat May 23rd, 2020 07:15 pm
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Steve Stephens
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William Dunlap wrote: A trap some folks fall into is not understanding that rectified 120VAC is actually more like 140VDC.
You could be overdriving your fan and causing damage. So, if your fans runs a lot faster on high speed, you should probably not run it there and just run it at the lower speeds.
You can also measure the VDC once rectified to prove this
Cheers,
Bill

Bill, I did a test using my Fluke meter and reading the voltage at one AC socket on this power strip and on the socket covered with red tape which has a bridge rectifier right under the socket.   The power strip is plugged into a Kill-A-Watt meter which is plugged into the Power Stat.   Did I do this test correctly?AC reads 120.2 voltsDC reads 115.6 volts






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 Posted: Sat May 23rd, 2020 10:54 pm
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William Dunlap
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I think testing pulsating DC is problematic without more sophisticated meters than what I have. I have your basic hardware store DVM and also a Kill-a-watt meter. But I don't trust that they know the difference. You could try both AC and DC settings to see what you get. I'm sure the readings will be quite different, but which one is accurate?
Cheers,
Bill

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 Posted: Sat May 23rd, 2020 11:31 pm
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Steve Stephens
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I'm no expert on electrical.  Bill Voigt who was very knowledgable never said anything against what I use.   It's a good idea to lower the voltage out of the variac when first starting any fan and raise it up to where it sounds good and the voltage measured is within a proper range.

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 Posted: Sun May 24th, 2020 12:04 am
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Bill Hoehn
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Come on electricians!

What happens when the rectifiers blow up and there is no fuse to blow? 
What happens to the unattended fan then? 
All of the old timers told me the odor when the selenium rectifiers blew was very strong and offensive..
I still use the old selenium ones and have an Emerson fan with them built into the top of the cage!
RUNS BEAUTIFULLY BUT LOOKS GROSS!

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 Posted: Tue May 26th, 2020 06:49 am
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Levi Mevis
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Bill Hoehn wrote: Come on electricians!

What happens when the rectifiers blow up and there is no fuse to blow? 
What happens to the unattended fan then? 
All of the old timers told me the odor when the selenium rectifiers blew was very strong and offensive..
I still use the old selenium ones and have an Emerson fan with them built into the top of the cage!
RUNS BEAUTIFULLY BUT LOOKS GROSS!

Yes, I'm very famliar with the old Selenium Rectifiers from all my years (about 20 that is) repairing and restoring old tube radios and I actually had an old Selenium Rectifier blow on me once on an old late 1950s vintage Zenith Tabletop Radio and it smells like rotten eggs when they blow, and can make you extremely sick if you breathe in the fumes too long.

That's why I like to try and replace those old Selenium Rectifiers in those old Radios with a 1N4007 Silicone Rectifier with a larger dropping resistor (if neccessary).

You can do the same with DC Fans or AC/DC Universal Fans by just installing a simple Silicone Rectifier in the plug of such a fan which would easily be hidden under the cover of the plug. 
(Credit for this suggestion goes to Russ Huber.) 

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