12V Car Vac for the layout

[Cajonpassfan]

I recently bought a 12V car vacuum for the princely sum of $18, the kind that plugs into the cigarette lighter, to use on the layout. It's got all kinds of nifty attachments to get into small spaces. (My old stanby, a battery powered DustBuster's exhaust is too close to the scenery, creating all kinds of scale wind havoc, and my other device, the shopvac, has just too much power, and a tendency to want to suck up things like shrubs, switchstands and automobiles, if one is not really careful).

This new car vac works really well, except I have no cigarette lighter receptacles on the layout fascia
So I cut off the plug and replaced it with a 12V, 1amp wallwart I happened to have.

My question is this: the device is rated at 120V DC and 120 watt "power input", whatever that means. When plugged in the wall, it runs at a lower rpm then it does on a car battery, so obviously the 1amp wallwart delivers less power. It's still plenty powerful for my layout cleaning needs, I don't want too much power for reasons already noted, but don't want to start a fire, either. The wallwart gets warm, but not hot. Am I asking for trouble here and should get a larger power supply to be safe, or is the only side effect diminished performance (which is perfect for my needs)?
Knowledgeable thoughts appreciated.
Otto K.

[Scottl]

I assume you mean 12 VDC.  At that voltage, 120 W = 12VDC X 10 Amps, so you would need a 10 amp power supply to match what it was designed for.  Most car ports have a 10A fuse associated with them.

[Lemosteam]

I bought this kit for my shop vac, reducer, extensions, brushes (I really like the wide one for cleaning up fine dust) and the crevice tool.  i do not find that the suction is too great- if it is there is sometimes a vacuum releif collar on the original hose end that can be opend to reduce the CFM at the tip:

[mmagliaro]

I recently bought a 12V car vacuum for the princely sum of $18, the kind that plugs into the cigarette lighter, to use on the layout. It's got all kinds of nifty attachments to get into small spaces. (My old stanby, a battery powered DustBuster's exhaust is too close to the scenery, creating all kinds of scale wind havoc, and my other device, the shopvac, has just too much power, and a tendency to want to suck up things like shrubs, switchstands and automobiles, if one is not really careful).

This new car vac works really well, except I have no cigarette lighter receptacles on the layout fascia
So I cut off the plug and replaced it with a 12V, 1amp wallwart I happened to have.

My question is this: the device is rated at 120V DC and 120 watt "power input", whatever that means. When plugged in the wall, it runs at a lower rpm then it does on a car battery, so obviously the 1amp wallwart delivers less power. It's still plenty powerful for my layout cleaning needs, I don't want too much power for reasons already noted, but don't want to start a fire, either. The wallwart gets warm, but not hot. Am I asking for trouble here and should get a larger power supply to be safe, or is the only side effect diminished performance (which is perfect for my needs)?
Knowledgeable thoughts appreciated.
Otto K.

I'm just guessing here, but I seriously doubt that the little motor in that car vac really draws 10 amps.
I bet that 120 watt "power input" was meant to imply that the vacuum would work when plugged into a standard auto cigarette lighter socket, which is usually limited to 10 amps.

Having said that, it probably DOES draw more than just 1 amp to really work right.  So you are overloading that wall wart, which is why it is getting warm and the vacuum runs slower.   Wall warts are also notorious for experiencing serious voltage drop when you draw anywhere near their rated current.  So a 12v 1A wall wart probably does no better than 9-10v when you get over about 3/4 of an amp.  I'd get more like a 3 amp 12V wall wart.  There are a few around with that much current capacity. 

Of course, to really do this right, you should hook that vacuum to a large supply (or even plug it back into your car's cigarette lighter socket) with an ammeter in-line and see what it actually draws so you know how big your supply really needs to be.  But my guess is that since it's "sort of" working on a 1A wall wart, it won't need more than 3A and that's probably overkill.

[Cajonpassfan]

Thanks for the thoughtful replies guys. It actually works just fine with the 1amp ww as a right of way and track vacuum, which is what I bought it for. I'm just concerned about safety and with my limited understanding of electricity, don't understand how the device could draw more current then the 1amp rated supply is able to provide...unless what you're saying Max is that the voltage drop is compensated by a corresponding amperage increase? And would that potentially cause the transformer to fail/burn up?
For what it's worth, it is plugged into a power strip that's only turned on when in use, along with some other devices.
Otto

[SandyEggoJake]

What Max Said...

In any case, be sure it is a switching wall wart.  Output shows the DC symbol of a bar over three dashes.  No squiggle symbol (AC) on the output descriptor.

[peteski]

Thanks for the thoughtful replies guys. It actually works just fine with the 1amp ww as a right of way and track vacuum, which is what I bought it for. I'm just concerned about safety and with my limited understanding of electricity, don't understand how the device could draw more current then the 1amp rated supply is able to provide...unless what you're saying Max is that the voltage drop is compensated by a corresponding amperage increase? And would that potentially cause the transformer to fail/burn up?
For what it's worth, it is plugged into a power strip that's only turned on when in use, along with some other devices.
Otto

Basically you are overloading the wall wart supply. You are putting more load (lower resistance load) than it can handle. As you already figured out, that causes the output voltage to  drop. It cannot draw more current than the supply can provide so the voltage (and motor RPMs) drop.  Most wall warts are simple supplies (transformer, rectifier, and sometimes a filter cap) so they can deal with a short duration overload withou overheating. But if you want to be safe, get yourself a wall wart with higher current output.

Look in https://www.allelectronics.com/category/914/ac-dc-wall-adapters/pwr-supplies/1.html . The sell 3A and 5A supplies for less than $20. And they have lots of other nifty electronic items too (which can be used in our hobbies).  Just make sure to get the power pack with DC output.

[MK]

Can't you put a decoder in it and reduce the RPM?   

[Cajonpassfan]

 
Funny though...
Otto

[learmoia]

Funny though...
Otto

http://www.digitrax.com/products/mobile-decoders/dg583s/

 

[Greg Elmassian]

120 watt would be high, but could be the peak power requirement.

120 VDC is clearly an error, since it says 12v and has a 12v car cigar lighter plug.

yes, 120 watts at 12v would be 10 amps.

I'm surprised it runs at 1 amp but maybe slowly... connect it to your car and see if it's not a lot faster.

It might well be enough vacuum with a 1 amp supply... just feel your wall wart after running it a while and see if it's getting hot.

Greg

[nkalanaga]

If you use DC for your trains, could you put clip leads on it and run it from your layout?

[peteski]

If you use DC for your trains, could you put clip leads on it and run it from your layout?

Only if his throttle can put out 10 Amps!   

[mmagliaro]

Only if his throttle can put out 10 Amps!   

Wait... this ain't a bad idea.  It probably does not draw 10 amps, and if it does, heck, the throttle's overload will just trip.   But assuming it draws more like 2 or 3, the throttle might be able to handle it.  If you have an ammeter, you could put that in line and then see what that thing really draws.

[peteski]

Wait... this ain't a bad idea.  It probably does not draw 10 amps, and if it does, heck, the throttle's overload will just trip.   But assuming it draws more like 2 or 3, the throttle might be able to handle it.  If you have an ammeter, you could put that in line and then see what that thing really draws.

Which DC throttles can put up couple Amps on the DC terminals?