USB powered desk fan

a standard USB port will only delivery 100mA before shutting down, you have to talk to the USB port to tell it you need more power, up to a maximum of 500mA. Measure your fan current, and see if it is less than

100mA, if not you need to put a micro inside your fan to talk to the port, not a trivial task

martin

Perhaps this would help you:

Although i think that dc-dc converters are a little expensive.

On a sunny day (1 Apr 2007 17:05:09 -0700) it happened " snipped-for-privacy@gmail.com" wrote in :

I have a 'USB powered fan', it crashed my PC USB port repeatedly before I soldered a AC adapter plug to it. Forget it, it sucks. USB is about 600mA max, and you likely have otehr stuff on it that uses some power. New mobo is expensive too... reboot is annoying.

30 Euro buys a huge Chinese fan with 3 speeds....

Why don't you just open the door of the fridge ?

Rene

Although the USB implementers would prefer it that way, many computers (probably even the majority of them) don't have such fancy current limiting on their USB ports and *will* pass a full 500mA (or more) to *any* device, such as a 100% "dumb" fan. Relying on this behavior obviously doesn't make for a robust design, but many ceahp USB "novelties" make use of that fact nonetheless.

I prefer using 110V when I in the mood for destroying the circuitry on my computer's motherboard. You can reach so many more subsystems that way.

I had suspected that, but I thought that I should try and point out the "correct" approach.

I'm not going to stick anything onto my laptop USB ports that is not "proper", but maybe with cheap USB cards for a desktop PC, who cares

martin

Oh that's mean, Rene.

Michael

Two words: extension cords.

wow. lots of bird walking going on here. i just want to know if i can put a resistor in series to reduce 5v to 3v and what the value of the resistor would be. if anyone has the ability to answer this question please help. otherwise please leave your 2 cents in your pocket.

That would be a ( 2 V / I_fan ) ohm resistor, rated at least ( 2 V * I_fan ) Watts.

--
Paul Hovnanian     mailto:Paul@Hovnanian.com
------------------------------------------------------------------
Stupidity kills. But not nearly often enough.

On a sunny day (2 Apr 2007 19:01:42 -0700) it happened " snipped-for-privacy@gmail.com" wrote in :

If you are such an idiot as not to listen to good advice WTF should anyone help you anyways. Now go an f*ck off.

I fit a USB to serial converter on almost anything with a microcontroller (especially when it is a prototype). No need for a bench power supply.

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl

Aw, c'mon, you haven't lived until you've shorted a kilowatt or so transformer and set the wire's insulation on fire! :-)

I take your point though... the other day I was thinking of making a little test board with a Max232-variant on it, when it occurred to me... hey... I might as well just use an FT232R, and that way I wouldn't have to come up with power from somewhere...

Many years ago I asked where a test lead had gone. A co-worker answered, "well it is right there" while pointing at a black stripe inside a transformer casing. They had been testing the transformer while I wasn't there and they shorted it using the test lead.

I have had very good results with the CP2102 from Silabs so far. Never quits, driver never hangs and it has an internal 5V to 3.3V regulator (100mA max).

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl

Ah, thanks for the pointer. I took a look at the data sheet over lunch, and while the CP2102 doesn't seem to have quite as many bells and whistles as the FT232R, I do like the fact that it has substantially bigger internal buffers (640/576 bytes for Tx/Rx vs. FT-232's 128/256), and it's nice that they provide various utility programs for customizing the INF files rather than making you hand-edit them as FTDI does!

you can run the 3V fan with 5Volts, it will just run faster

When the bearings fail, so does the motherboard.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida