Help!! Train power from a Car Battery?

A friend of mine is looking to power his N scale train from a 12 volt car battery. Anyone know of some where to buy a control that will allow this? I made him one using a LM317 voltage regulator, but it's minimum output is 1.2 volts and the friend is looking for something that will go from 0 volts to the full 12 volts of the car battery. Any help is greatly appreciated. Please email responses to: snipped-for-privacy@aol.com Thanks

Reply to
Trapshooter870
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LOL!!! Planning on taking your trains with you on a long car trip?

Kent in SD

Reply to
Two23

Whatever you do, BEWARE THE AMPS! A model train power pack puts out NOWHERE near the amperage a battery will; a battery can easily kill you.

Reply to
Brian Paul Ehni

It only requires 2 diodes to supress the 1.2volt output that the LM317 puts out. Look here:

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Works very well. The voltage drop across the two diodes in the output allows the voltage to go to zero (as viewed by the trains).

Your currents to the track will still be limited to the capacity of the LM317 (or LM350 which is 3 amps). However, short circuits between the car battery and the regulator circuit are something else.

Hope this helps. Bill K. Houston

Reply to
ZBendTrack

I would recomend about two minor changes that come to mind with a quick glance at the schematic. The 3300 uF capacitor should be replaced with about a 10 uF tantalum and a 0.1uF ceramic in parallel with each other. This will reduce the chances of oscillation in the regulator.

To clarify how to hook this up the part labled cr-1 is where the battery hooks up. See the + and - signs on it?

PUT A FUSE BETWEEN THE BATTERY AND THE POWER SUPPLY!!!!!!

Ooops, was I shouting there? Good reason. A car battery can put out several hundred amps if it is short circuited.

To do reversing on the track use the standard wiring of a switch to make it work. A double pole double throw switch will work there.

Reply to
Allan Butler

snipped-for-privacy@aol.com (Trapshooter870) wrote in news: snipped-for-privacy@mb-m12.aol.com:

I have an old Tab book "Model Railroad electronics" that has some designs for throttles that run on 12volts. It may be a bit of a reach, but a Google search for "true Action Throtle" or TAT might turn up somthing. I seem to remember there being several TAT desigs up to TAT-7 (IIRC).

Anyway, if you are wanting to experiment, you can build a throtle simply with a NPN power transistor (TIP-??) and a potetiometer. Connect one end of the pot to +12. Connect the other end to -12 Connect the wiper to the base of the transistor. connect the transistor C to +12 Connect the transistor E to the track. the other side of the track goes to -12 The throttle is basicly a big voltage follower. If you want the trains to run in both directions then you have to hook up a reversing switch between the transistor and the track.

This design will go from 0volts to about 11.4 (12 - Vbe).

Reply to
Gordon Reeder

Thanks for all of the help. I am going to build the circuit using the LM350 IC and the two diodes on the output. Steve

Reply to
Trapshooter870

Though not as cheap, your friend could also just purchase a standard converter at an auto supply store. That way he could use his regular train transformer with all it's features.

I power my show display from a car battery, including my 2 n scale display layouts and all my special effects boards. It's a lot easier just to plug the various transformers into the converter and not worry about it.

Mike Tennent "IronPenguin" Operating Traffic Lights Crossbucks Special Effects Lighting

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Reply to
Mike Tennent

Why?

Reply to
Biggus

Reply to
Charles Kimbrough

A 12 volt automobile battery cannot easily kill you. It CAN under some bizarre circumstances cause death or serious injury but it cannot "easily" kill you. The

220 Volt 60Hz stuff in your breaker box can kill you a whole lot easier and quicker than any 12 volt car battery. The battery can only kill you with the greatest of difficulty. You must help it along quite a bit to achieve such an end. The most probable injury is a minor burn caused from being part of a short circuit.

If you burn your skin off or stab through it then the resistance across the whole body under the skin is only about 500 ohms; even less, if you stab deep enough. So if you take a couple of sharp probes, connect them to a 12 volt car battery, and stab them into your chest, you'll be in a bad way. However, if you do that it is evident that you were already in a bad way to begin with.

Now, while it may be possible (perhaps) to show documented proof of death as a direct result of electrocution from a car battery, it is not something that is a serious problem. Batteries are no more dangerous than the electrolyte inside and the hydrogen they outgass as a result of their function.

Read this:

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As anybody who's managed to jam his stainless steel watch bracelet between the positive terminal of his car battery and the negative-ground frame will be able to tell you, car batteries can deliver quite a lot of current.

Automotive starter motors operate on 12 volts DC, and can draw hundreds of amps for the (with any luck) brief period when the engine's cranking. Let's assume the battery delivers exactly 12 volts, and exactly 240 amps is being drawn. With that information, you can use Ohm's law to figure out the resistance of the circuit (including the starter motor, its wiring, the internal resistance of the battery, et cetera). R equals 12/240, or only 0.05 ohms. And the circuit power, mostly accounted for by the motor, is 12 times 240 - an imposing 2880 watts.

If 240 amps passes through any significant amount of a human body for any significant period of time, investigators may have to employ DNA analysis to determine who that stuff they found all over the place used to be. You really don't want to make yourself part of a 240 amp circuit. Actually, only about 30 milliamps (0.03 amps) across the human heart has a good chance of stopping it.

Where people go wrong, here, is by thinking that if you disconnect one battery lead in your car, hold the end of that lead in one hand, touch the battery terminal with the other hand, shout "Je ne regrette rien!", and then get a partner in scientific exploration to turn the key, you'll be deader, faster, than someone who's already started his skydive when he discovers that the thing on his back actually contains some chocolate and a sleeping bag.

What will actually happen in the above situation - the car situation, not the skydiving one - is nothing.

The reason for this is that the human body has quite a lot of resistance of its own. If you've got a good contact - the terminals are big enough that the whole palm of each hand can touch them - then the resistance across your body is likely to be between about 2,000 and 50,000 ohms. The thinner and wetter your skin, the lower the resistance will be.

Even if your resistance is only 2000 ohms - which it probably won't be - that's enough to drop the circuit current to about 6mA. You may be able to feel that. You probably won't.

Since your resistance is actually likely to be much higher, the current through your body is likely to be trivially low. And since your body is part of the circuit, the current through the whole circuit will also be trivially low. Hence, the car will not start, and you will not die.

But beware! You can most certainly fry one of those little flea sized N scale locomotives if you do not include some kind of over-current protection such as a fuse or a crowbar curcuit. Fuses are OK and they are cheap. Crowbars are more complicated and expensive but work much quicker. You may still ruin a locomotive even if you pop a fuse. Not really very likely, but the slim possibility does exist.

Don't open the batteries and expose yourself to the electrolyte. It's not a crime, but there's no future in it. You can get nasty acid burns if you're careless or accident-prone.

Don't allow hydrogen gas to accumulate in closed spaces unless you live in Lakehurst New Jersey or your name is Hindenburg. and be sure to vent the inevitable acid vapors that are an integral part of lead-acid batteries. You can buy sealed batteries these days that cannot be opened and that will not spill. That is what I would recommend, but I would still vent them to the outside if possible

NOTE: some of the comments above were C&P from

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and some are truly my own. I have messed about with automobile batteries for fifty years and have never been killed by one. Not even injured.

Reply to
Froggy

Good point. Since I have to transport all my stuff, I never considered using anything other than a sealed battery.

Mike Tennent "IronPenguin"

Reply to
Mike Tennent

While I agree with what you say, there's a LOT glossed over in your last sentence. "Batteries are no more dangerous than the electrolyte inside and the hydrogen they outgas as a result of their function."

Electrical burns are only part of the problem with short circuited car batteries. The internal resistance of the battery will limit the current to some finite value ... in the process it will generate a LOT of heat IN the battery. This can be enough to boil the electrolyte and cause a steam explosion of the battery case. This sprays scalding-hot battery acid and hydrogen gas all over the place, along with plastic and lead 'shrapnel'. NOT good! A secondary hydrogen 'explosion' (see below) is a possibility.

More typically, however, hydrogen is vented during the charging process. If not well ventilated, this can also cause risk of a hydrogen ignition. Unless tightly confined (in a battery 'box' or similar), this is unlikely to result in much of an explosion, but could easily ignite other nearby items. It might also burst the battery case, with results similar to those above.

A car battery can certainly be used for the suggested application. It was common to do so in the 1930's and 1940's. As many have stated, caution and proper use is necessary. A fuse MUST be fitted to the battery, as close as possible to one of the main terminals (probably to the positive one, as the negative is usually considered 'ground'). The main terminals, and ANY wiring ahead of the fuse should be well insulated and protected from accidental contact with (dropped?) metal items. The battery should be in location away from where most persons frequent, and well ventilated (especially during charging). The best ventilation is to OUTDOORS! Perhaps a screened back porch or similar might make a decent location (depending on the climate, but batteries work well to below freezing temperatures).

As a side issue, hydrogen gas vented by the battery can build up in space as large as an entire home. Probably not to dangerous levels, but it can still cause problems. For one thing, it will set off carbon-monoxide detectors (BTDT) ... this can lead to moments of excitement until the problem is correctly analyzed. :-(

Dan Mitchell ==========

Froggy@The, P>

Reply to
Daniel A. Mitchell

Well, yeah, that's right, but I'd already written a dissertation on the subject and my fingers were starting to get raw. So, I wrapped it up.

I have never, ever, never exploded a battery. In fifty years not one. While such is possible, the likelihood of it happening is quite small.

The point is, that it is highly unlikely that a car battery will kill you unless dropped on you from a high altitude. Properly used they pose no threat to your well being. Improperly used.........well..........there is no defense against stupidity, ignorance or carelessness. I would suggest that if one thinks he might be stupid, ignorant or careless that he refrain from doing things that require intelligent thought and planning. Of course I fully realize that such a suggestion is completely wasted.

Of course, in a more perfect world, you would have an 18 Volt 10 Ampere transformer with a 250 Watt capable rectifier on the output. This would feed a regulator circuit built around an LM7812 voltage regulator controlling a 2N3055 pass transistor. Voila! a steady 12 volts with up to 10 Amps if needed. Enough current to run a gargantuan N scale railroad, but not enough to weld trucks and motors to the track.

Never the less, it is entirely possible to use batteries with sufficient safety to run a model railway. It merely requires a bit more thought and planning than using the power company and a transformer.

..............F>

Volta Cell, GA.

Reply to
Froggy

Add two IN400(1) diodes in series to the output before the reversing switch. You started with 13.8 volts so the maximum output voltage will now be 11 volts which is reasonable.

Reply to
Gregory Procter

On Tue, 27 Apr 2004 18:36:15 UTC, Froggy@The Pond.com wrote: 2000

Reply to
Ernie Fisch

A car battery provides 12 volts DC, pretty low voltage. However, the current it can provide is about 240 amps. The car circuitry (starter motor wiring, inside of battery, connecting wires) has a resistance of about 0.05 Ohms (12 v / 240 amps = 0.05 ohms). The power delivered to the starter motor is 2880 watts ( 12v X 240 amps = 2880 watts). If you grab both terminals of a car battery, the resistance of your skin (2000 ohms or more) will drop the circuit current to 6 milliamps (I = 12/2000 = 0.006 amps), not enough to feel or injure you. Take that same battery and use sharp probes to stick into the chest under the skin to a lower circuit resistance (500 ohms) and now you can be harmed (24 milliamps).

Reply to
Brian Paul Ehni

On Tue, 27 Apr 2004 18:36:15 UTC, Froggy@The Pond.com wrote: 2000

From my college days I have a recollection that a low current, approximately 10 mA, passing through the chest can affect the diaphragm causing it to stop. So while technically not electrocution (you die of asphyxiation) it can kill. I do not remember the exact numbers (hey, it was more than 50 years ago) but they are in that ballpark.

Since most of us have messed around with 12 volts a lot it is not a common cause of death but it has apparently occurred.

Reply to
Ernie Fisch

It ain't the volts; it's the AMPS. Static electricity is 10k to 30k volts, but almost zero amps.

Reply to
Brian Paul Ehni

such is possible, the likelihood of it happening is quite small.< Two points, years ago I saw my cousin explode a car battery, he was trying to jumper it in front of the house. Lost a good suit, lucky he wore glasses. Second point, mechanics always used to take off all rings. A possible short could really produce a bad burn on the ring finger.

But the real point with model railroading is you must fuse it to the layout. Other wise any short _could_ be exposed to a few hundred amps. That's _hundred_ again.

Reply to
Jon Miller

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