I have a small fan that is used to exhaust air from a work station. It runs on 12v DC 4.5 amps.
I was told that there are four ways to effectively power this fan on household current, and do so safely.
One was to buy a power converter from Radio Shack (the cheap ones) and wire it to the 12v.
Two, was to buy a power pack- the kind that is used to jump start batteries, and use that by wireing a cigarette plug to the end of the fan and plug it into the power pack and basically leave the power pack plugged in and run the fan off of the pack all the time (24/7).
Three was to use the power supply used TO charge this battery jumper pack- which is rated at 13.5v 300 amps.
Four was to wire the fan to a power supply used for personal computers.
Replacing fan with AC fan NOT a possibility to consider at the time, this DC fan is only functional device sutible for application- mostly in the design and utility of the fan.- but "thanks"...
Just go to Radio Shack and buy a suitably rated nominal volt power supply and connect the fan. It will be safe, cheap, effective and easy to connect. One of the types designed to allow car equipment to be used in the home, if it is rated at 4.5 A, at least, will be fine.
Using a computer power supply with adequate rating could be ok - but you would need the right connectors to wire it up and not all of them are suitable for connecting only to a 12 V load. They are also designed to be mounted inside a computer case and wouldn't be as safe or as tidy as a unit intended to be self contained.
Using a power pack is an unnecessary expense. If you do, make sure the outlet is fused appropriately. There is enough energy stored in one of these units to start a nice warm fire, very quickly.
The charger unit for the power pack may not be rated to provide 4.5 A. These normally charge over many hours at a relatively low current. Even if it is rated at 4.5A output, it may be highly unregulated and produce too high a voltage for your needs. The panel on the charger should tell you its output voltage and continuous current rating. It may also need a special connector for the fan wire. So, it may or may not do the job.
So, I would stick to a nominal 12 volt 4.5A regulated supply from Radio Shack, or equivalent.
radio shack power supplies: not suitable for any industrial application (in my opinion) based on experience.
the expense of a (electronically) regulated supply is unnecessary.
battery chargers make terrible supplies (usually). they charge batteries well and that's about it. way too high no load voltage to be useful and high internal resistance in the secondary.
for 7/24 operation use a supply that is rated for twice the operating current (at a minimum).
wire the fan to the supply (no plastic automotive type plug - they melt)
To clarify the size of the fan, here is a link to a similar fan- it is the only thing I could find that would effectively remove the fumes from the area in which I am working-
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It says that it draws 4.5 amps- but I was wondering if this only acts as protection from surges when intially started, but then draws fewer amps as the motor runs.
Ahhh... what you thought you wrote isn't what I thought I read.
I understood "small fan" and "work station" to mean a typical little muffin fan in a PC. You mean a nice little blower for a work *area*!
That changes everything. Do *not* try running that from your PC's power supply! (Although it might work, and if you do happen to have an extra PC supply laying around, it will probably handle it OK, though there are some tricks to getting it to run.)
You could buy a "battery charger" that is meant to supply something like 6 amps or so. Stay away from anything larger than perhaps 10-15 amps, because you aren't going to load it enough and the voltage will be high. (However, it appears the fans you are looking at, while labeled "12V" are actually meant for use on a system with a 12V battery, where the voltage is usually more like 14 volts.
Whatever, make sure the supply can handle the current on a _continuous_ basis. Or go for 50 to 100% higher if it is rated for intermittent use. But stay away from things like 300A boosters... ;-)
The best way though... You can find any number of very nice power supplies that are listed as "battery eliminators" and are designed to power radios and other equipment meant for automotive or marine use. If you get one of those, they usually have a voltage adjustment, and current limiting (which might even be adjustable). It won't make much difference what the maximum current rating is, as long as it is high enough to power your fan. Hence if you find a good buy on a 25A unit, go for it. But a 5A unit would be fine too. Since the voltage is adjustable, you can set the fan to run at just about any speed you want. If noise is significant, you'll find that to be a
Yep, look in Radio Shack for a power supply designed to run car equipment off the mains supply - typically used for powering cb radios and the like. That will do it nicely, if it is rated at 4A or so continuous.
You could just use a car battery charger - which will be cheaper. Some need to detect the battery voltage before producing power - you don't want one of those. The fan is intended for battery systems which produce voltages of the sorts of value you will get from a charger - so a charger should work fine.
You can also get dc output switched mode power supplies intended to power 12V domestic halogen lights. They are very lightweight and very cheap in the UK - but make sure you get one with dc out. I bought some
100W ones at around 8GBP each. They are fine for driving motor loads as they are designed to cope wih high starting currents.
Find a 12.6 volt filament transformer rated for twice your running current. Attached to it full wave bridge rectifier rated at four times your running current. Put them in a nice box with a power switch and a circuit breaker rated at 125% of your running current; it will handle the starting surge.
The hefty transformer may be hard to find for a reasonable price; it's cost alone may equal the price of your fan. Or go surplus shopping at places like MPJA
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or Electronics Goldmine, or the like and look for a DC supply. A 12VDC supply rated for 4.5 amps may be quite expensive if it is regulated.
The best best would be to buy a 12VDC 6amp auatomotive trickle charger. But you will pay at least the price of your fan for that.
I wish to thank all of you for your input on this situation! It seems I have a few options to consider, now the only issue is finding the materials that you specified to do the job- both cheaply and safely!!
As far as the cost to run the fan equalling the cost of the fan itself, not a real issue- in that, the other options I had recieved from electricians in my area were at least three times the cost of the fan itself.
I have considered using fan that is AC- but none I have found have the CFM rating of this powerful little fan, and even then- it was quoted that the fans do not pull air, but only move air already present in the tube- not creating a vacum like effect but only moving the air.
Since the work area I am working in is not air tight, a vacum of great intensity is required to move the fumes away from me- that is why I chose this fan- as a plus- it was relatively cheap. I am mostly looking at the design of the fan itself and the propulsion of the blades as the main factor for going through all of the issues that circumvent using this piece of equipment- ie. the ones that you have all addressed in helping find a way to power this little "sucker"- yes, pun intended! :)
Thank you all again, you have been VERY helpful!!!
Thanks to a suggestion from this board- would this device would be appropiate?
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States the following about the device;
4 Amp Regulated 12V DC Power Supply with Cigarette Lighter Adapter (PSR-4C) Our 12 volt 4 amp power supply is regulated and has filtered outputs. It features a 5 amp surge, cigarette lighter adapter, built-in front panel, fuse and auto reset circuit breaker overload protection, heavy duty 3 prong grounded AC power cord, and universal binding posts. It has a 117V AC 60 Hz input and a 12V DC ouput with a 4 amp constant and 5 amp surge.
I would be happy to use one of these. It has an auto-reset circuit breaker which will protect things if the fan is slow to start or has sucked something in to its blades. If the fan had been a lot bigger, with more rotational mass, the starting current could have been a problem but with small fans like this, combined with an auto-reset thermal circuit breaker, it won't be an issue. Enjoy.
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