Need Some Electrical Expertice
#31
BiL:
I don't think you can "step down" 10 amps. You can put a fuse in the circuit but you can still get the 10 amps until it blows. Even dividing it up between 2 throttles, if one only needs 2 amps the other one could pass the other 8.
(Someone else may have better experience of this than I do.)
David
Moderato ma non troppo
Perth & Exeter Railway Company
Esquesing & Chinguacousy Radial Railway
In model railroading, there are between six and two hundred ways of performing a given task.
Most modellers can get two of them to work.
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#32
BR60103 Wrote:BiL:
I don't think you can "step down" 10 amps. You can put a fuse in the circuit but you can still get the 10 amps until it blows. Even dividing it up between 2 throttles, if one only needs 2 amps the other one could pass the other 8.
(Someone else may have better experience of this than I do.)

think of it like your house - you likely have a 150 amp or greater main breaker, and 15 or 20 amp breakers for most of the rest of the circuits. potentially, 150 amps could be supplied to your house at any given time, but more than likely it is less than that. But, you don't want 150 amps running through any given circuit, because if there is a short somewhere, it will fry the wiring in your house or in whatever appliance has the short circuit. So, they divide the 150 amps into smaller circuits with smaller breakers. A 14 gauge wire can easily handle 15 amps, but is TOAST at 150 amps. For your model railroad, you could do the same thing - divide the 10 amps into two 5 amp circuits protected by fuses. Or, you could have only one circuit with a 5 amp fuse, and the other 5 amp capacity is unused. Basically, if there is a short circuit, it will use whatever amount of current is available until something burns up.
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Kevin
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#33
amp flow is like water if you have a 10,000 gallon tank and you put three valves that have a flow of 12 gpm at 25psi take the same three valve and put them on a 200 galon tank you still only get 12 gpm per valve as long as the pressure is 25 psi, so no matter what the potential is the valve (fuse) limits the amount of flow.

jim

you beat me to the punch Kevin.
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#34
It looks to be just fine. As many have mentioned, just be sure to put in some form of protection to your layout (fuses) so that in the event of a derailment or whatever, the chances of something cooking are reduced. :-) A 5A supply is what I use to, but my layout is devided in sections each protected with a 1A fuse. The power supply is therefore strong enough to supply the layout with trains running at different spots of the layout, but each individual section has a 1A limit. For my current use that's more than enough, but if you run big heavy trains with multiple powered loco's, you may want to see what that train pulls in electrical current when running, and base your fuse sizes on that.
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#35
Ahhh! Kevin ... That started to make some sense. I'll read that I few more times aand I'll be on my way to understanding ... hopefully!
biL

Lehigh Susquehanna & Western 

"America will never be destroyed from the outside. If we falter and lose our freedoms, it will be because we destroyed ourselves." ~~Abraham Lincoln
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#36
P5se Camelback Wrote:I don't know that I'll ever get it! Now Don, in a very kind attempt to explain, has introduced a fourth word into the mix! Now we have Ohms, Amps, Watts ... and Current. I read Don's post three times and the only thing I can tell you is ...I'll bite ...
Current is measured in amps, just like resistance is measured in ohms, voltage in volts and power is measured in watts. Ohm's law gives you the relationship between volts, amps and ohms. Power is obtained by multiplying the volts times the amps.
P5se Camelback Wrote:Wall Wart ... that is one of these little power supplies like the one that powers a really cool lamp that I have ... it's a 1 1/4" x 1 1/2" x 2 1/2" black thing with a two spade connectors at the end of a long black cord that plugs into the lamp which uses an High Intensity lamp.
Yes, some are simply transformers with a low voltage AC output, others will deliver DC output at various voltages and degrees of regulation. Do not assume that all wall warts are the same, you have to read their output specs, and polarity (yep, yet another new word). Polarity is simply, is the positive terminal on the inside or outside of the plug.

P5se Camelback Wrote:... and I guess my original question here was can you step down 10 amps to something lower that is safer to use?
You cannot, "step down", current (amps), you can only limit it by using a fuse. You can step down voltage by various means, but not amps. If you have a power supply that will produce 10 amps, then that is what you can get unless you put a fuse in the line that is less than that. You will only get the amount of current (amps) that the device you are powering will require. So if you are powering a lamp that will draw 500 mA with a 10 amp supply, you will have 9.5 amps left to power other devices without overloading your power supply.
Don (ezdays) Day
Board administrator and
founder of the CANYON STATE RAILROAD
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#37
Thanks, Don. I'm starting to understand, a little bit. I'll have to go back and review several times over the next couple of days in an effort to reinforce the understanding. :?

It's still early in the semester ... hopefully by mid-term exam time I'll have at least a minimal handle on it! :?

Thanks, guys, for your extreme patience! Visual stuff I grasp quickly, often before the explanation is complete. but things I can't see and have to understand based purely on the verbal ... it's a crap shoot! But you have all been very patient and helpful ... I appreciate your help.
Thumbsup Cheers Cheers Worship
biL

Lehigh Susquehanna & Western 

"America will never be destroyed from the outside. If we falter and lose our freedoms, it will be because we destroyed ourselves." ~~Abraham Lincoln
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#38
I think powering a 1 amp device with a 10 amp power supply is kind of like drinking out of a fire hose. That fire hose is going to put out a lot more water than you can possibly drink. The device is going to determine how many of the available 10 amps are actually used. The rest of those amps will just sit there until some other device needs them. a short circuit will demand all of the power that power supply will put out and then some if it can. That is why you need a fuse in each circuit sized to slightly exceed the power demand of whatever is running on that circuit. If you put a 2 amp fuse on a circuit with a device requiring 1 amp, you will have twice as much power as needed for the device, but the 2 amp fuse will blow and shut down everything in the event of a short before other damage is done.
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#39
O.K., guys ... thanks for all your patient explanation! Between Russ and Don and Kevin and Gary I am actually starting to grasp the concept!

I should probably gather up the 10A Power supply and the Tekin battery charging stuff and pin a "for Sale" sign on the bulletin board in the new (4 month old) LHS that caters to R/C race cars. I was there two days ago to buy a package of Plastruct strip stock (for roof ridge joint bracing) and the tow mid-twenties guys working in there were not exactly the picture of outgoing and friendly -- it was almost a chore for them to ring up my sale! I'll order on-line from now on unless it's an emergency!

If it were my shop, and it was called to my attention that an employee had found it to be too much trouble to engage a customer in conversation, get to know his name, identify his interests (especially if it's 4:30 PM and no one else is in the store) and invite him to come back again, you would get your one-and-only warning to wise up and to help build the business or not to bother coming in any more!

O.K. ... there you have it ... my esteemed thanks to all those who bothered to offer assistance to help another modeler understand electicity ... and my "I get so annoyed when ..." rant for the day!
biL

Lehigh Susquehanna & Western 

"America will never be destroyed from the outside. If we falter and lose our freedoms, it will be because we destroyed ourselves." ~~Abraham Lincoln
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#40
I have to agree with Russ, too much power is not always a good thing. If the supply can't limit the power (I have one where you can adjust the max current output), then you need to put a fuse in line to keep from frying the device before the current will max out.
Don (ezdays) Day
Board administrator and
founder of the CANYON STATE RAILROAD
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#41
One other thing I thought of regarding fuse protection. It is tempting to install a circuit breaker instead of a fuse. That is fine if the circuit breaker requires a manual reset. I retired from Carrier Transicold repairing transport refrigeration units. Typically we would have fuses in the units, but some people got tired of replacing fuses, because they did not find the root cause for fuses blowing. They would install automatic resetting circuit breakers thinking that would solve the problem. The problem was that a circuit breaker that is constantly tripping and resetting will overheat and fail. If it fails open, your ok. If it fails by having the points weld shut, you have just lost all circuit protection!
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