So I have a 12vdc/2amp computer fan that I am trying to power with a 9vdc/1amp wall power adapter. My fan has red, white and black braided wire going into the fan and the wall charger just had a positive and negative. I placed positive to positive and negative to negative and left the white (ground) out. My fan will start up and spin for a second and then quit and repeat that cycle. Am I wiring something wrong or do I need more volts/amps from the wall adapter? Any help appreciated.View attachment ImageUploadedByHome Brew1459192425.329984.jpgView attachment ImageUploadedByHome Brew1459192499.554101.jpg
DIY stir plate problem?
- Thread starter jgoodhart
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That fan is trying to pull 100% more wattage than the adapter is supplying. You can't do that. Don't use that adapter. You will, at best, burn out the adapter; at worst, it'll burn up and start a fire. That is more than likely what is causing the problem. You can go with a higher-powered adapter than the fan, but not the other way around.
UndeadFred
Well-Known Member
Likely you need a bigger supply, but there are not many if any computer fans rated 2A at 12V. Are you sure it's not 200mA? I use 12V squirrel cage blowers myself so I can do gallon jugs for lagers and those bad boys are only rated at an amp.
Most fans, especially when run horizontally (which is bad for all but certain ball bearing fans and rifled bearing fans), will also have a startup surge of about 20% more than their rating.. if the supply can't handle the surge, it will attempt to start and then die.
MOST Chinese switchers are grossly overrated in what they can actually deliver.
I really need to find another cheap variable bench supply to recommend for a 12V adjustable supply. I had one at a surplus place for awhile but they ran out and replaced it with a stepped voltage supply.
Using a potentiometer works on smaller fans but isn't really a good way of doing it. (Linear taper pot? Logarithmic? Bigger fans will draw more current through the pot than it is rated, etc.) You want to make your stir plate speed adjustable and with cheap DC motors you can only do that by variable voltage. More expensive ones (the four wire ones) can be PWM'ed by an external controller but that limits you to only a smaller amount of fans.
Most fans, especially when run horizontally (which is bad for all but certain ball bearing fans and rifled bearing fans), will also have a startup surge of about 20% more than their rating.. if the supply can't handle the surge, it will attempt to start and then die.
MOST Chinese switchers are grossly overrated in what they can actually deliver.
I really need to find another cheap variable bench supply to recommend for a 12V adjustable supply. I had one at a surplus place for awhile but they ran out and replaced it with a stepped voltage supply.
Using a potentiometer works on smaller fans but isn't really a good way of doing it. (Linear taper pot? Logarithmic? Bigger fans will draw more current through the pot than it is rated, etc.) You want to make your stir plate speed adjustable and with cheap DC motors you can only do that by variable voltage. More expensive ones (the four wire ones) can be PWM'ed by an external controller but that limits you to only a smaller amount of fans.
I have a 22vdc/200mA power supply and a potentiometer. I was under the impression you didn't want to supply the fan with more than the 12vdc? Will this adapter work with the 12v fan and potentiometer? Any risk of burning the fan motor up or starting a fire? View attachment ImageUploadedByHome Brew1459195239.905294.jpg
You need lower voltage, higher amperage.
Dig around and get a 12v psu somewhere. Check the local thrift stores if all else fails. Over voltage protection is probably kicking in on the fan.
There no such thing as to much amperage. Wont hurt anything. To little will.
Dig around and get a 12v psu somewhere. Check the local thrift stores if all else fails. Over voltage protection is probably kicking in on the fan.
There no such thing as to much amperage. Wont hurt anything. To little will.
I suggest getting a fan that doesn't burn 20-something watts just to spin a magnet...
Cheers!
Cheers!
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UndeadFred
Well-Known Member
Get a 12V supply rated at 1A or better. And, sigh, I guess the proper potentiometer. You really need to make the plate variable speed. If anything, you can buy them for about $10 off of e-bay. Again I'd recommend a variable supply but I can't find one that I'd recommend for less than about $35 now. I'll update the group if that changes.
AkBrew907
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Get a thermaltake usb controlled fan. Don't have to worry about wiring and nearly everyone has a USB wall adapter for charging phones and other accessories that you can plug it right into.
You can see it in this picture before I took it apart and mounted it in my box.
And all completed
You can see it in this picture before I took it apart and mounted it in my box.
And all completed
UndeadFred
Well-Known Member
How big of a flask can that little USB fan handle? My only fear with recommending that is, "can it do a 5L flask?" .... Can it? If so.. yup that is the easiest and most correct solution to recommend to others. Report back, please. I personally use a BIG 12V almost 1A squirrel cage blower with one of my variable ham radio/electronics experimenter supplies.
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