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I am into a project that is line powered but needs a 12VDC fan, for compactness and size.
So the dilemma is what means to derive the 12VDC/200Ma for the fan:

I have the following options in mind, in no order of preference:

Conventional transformer power supply
Direct line power with series dropping resistor and rectification
Direct line power with series capacitor and rectification.
Conventional line rectification with a high voltage regulator (TL783)
Conventional line rectification with zener pre-regulation and a common 3 termnal regulatot (LM7812)

Notes:
The power supply must be cost effective compared to off the shelf units
There is always an issue using non-isolated line power, but this fan is inside a grounded enclosure.

Open for comments or more options!
Thanks,
Len

Wait.......

What is the physical size needed for the fan?

If it isn't too small, you could still use a small AC fan.


Signed: Janitor Tzap

Hi,
The fan is like a common axial PC fan, no tach leads, just power. It is 80 x 80 mm but only 15mm thick, and draws 180ma.
Here it is:https://www.arrow.com/en/products/od801 ... orion-fans

There is no room for a thicker fan, and the enclosures are already tooled for the 80mm size.
What happened is that that the older model had a 12VDC power supply, for other reasons, so it powered the fan.
This project has no need for DC except for the fan, so a dedicated supply is needed. This is a low quantity need, so building them is not an issue...

I looked all over for a 120VAC fan and in that size 25mm was all that was found. Your interest is appreciated, and if you find a gem under a rock, let me know!
Of the power supply design ideas I presented, do you favor one over the other? Since this is a low quantity need, building them is not an issue.


Thanks,

Len

Lenp wrote:Hi,
The fan is like a common axial PC fan, no tach leads, just power. It is 80 x 80 mm but only 15mm thick, and draws 180ma.
Here it is:https://www.arrow.com/en/products/od801 ... orion-fans

There is no room for a thicker fan, and the enclosures are already tooled for the 80mm size.
What happened is that that the older model had a 12VDC power supply, for other reasons, so it powered the fan.
This project has no need for DC except for the fan, so a dedicated supply is needed. This is a low quantity need, so building them is not an issue...

I looked all over for a 120VAC fan and in that size 25mm was all that was found. Your interest is appreciated, and if you find a gem under a rock, let me know!
Of the power supply design ideas I presented, do you favor one over the other? Since this is a low quantity need, building them is not an issue.


Thanks,

Len

I would suggest you go with a Halfwave Power Supply.
Since It is only powering just the Fan and nothing else.

Or

Problem with the Halfwave is RF noise and heat being generated.

I haven't found a AC FAN that thin so far.
I still need too check several surplus places.


Signed: Janitor Tzap

what about a cheap SMPS ( the new wall warts ) i get em all the time at flea markets for a dollar or 2.. just look in the
junk bins..

I can't use surplus or cast off components. This has to be a solid design with repeatability and documentation.
A $2 special from 'Sam's Transformemporium' may be a great buy, but it will not pass muster.
Like everyone else, I have bulging bin fill of wall warts, of any description, and if if was for one of a kind, it would be done and no need to make the post.

I am trying to stay away from a transformers if possible. If you priced them recently you'll know why. A Triad 12V 0.35A is $10 in singles! I buy quality switchers with a 2 year warranty, A universal input, and 60VA output unit for $13 in singles, and off brands are even less. Copper is out of sight again, and aside from that, a transformer makes it too easy!
I doubt if the brushless fans would even like the unfiltered ragged half wave power:razz:\

Len

Probably saw some of these transformerless AC-to-DC circuits:
http://www.brighthubengineering.com/diy ... ly/#imgn_2

DUMB ME...DILEMMA DONE!
After all is said and done, I scrapped the fan power DIY attitude and found the best answer.
Here is a PCB mount SMPS, 12V/250ma, with a ton of features and approvals, all for $5 in singles!!!
And, it is stocked on this side of the pond.

Here's the gem ...http://www.trcelectronics.com/View/Mean ... 3-12.shtml

that's probably essentially what is inside newer wall warts. good choice

Now I see them everywhere-
http://www.digikey.com/product-detail/e ... -ND/658557

Hi, and thanks for your comments.

Yes, they are like that new 'special' car you buy, then an identical one pulls up next to you a block from the dealer!

I saw the model you linked to, and a look at the application sheet shows it needs a fair amount of support architecture. I also don't care for its high riding profile with the SIP arrangement. The unit it will be used in is shipped worldwide so I question that mounting integrity without a silicone blob to nail it to the board. Not that it matters, but the input voltage is also lower. (170VAC)
The Meanwell unit is a low profile rectangular package with 4 active pins and 1 dummy locator pin. It is plug and play. No support components needed unless you want to fuse it, and its input is 80 to 370V. $5 in singles, stocked locally, 2 work days from order to door and then kick in a factory 3 year warranty.....




The difference between crazy and eccentric is...An eccentric has money!

Good find !! Dontcha love it when a plan comes together !!

Remember, all plans come together.
Some good, and the others, we don"t talk about!