Given an HO DC diesel, on an old bulb-type incandescent light, was the base (bottom) of the bulb housing positive and the side "jacket" portion of the bulb housing negative- or the opposite?
This is for purposes of substituting a resistor+LED light in place of each of the existing old bulbs.
Cedarwoodron
The polarity would depend on running forward or reverse. Check with your voltmeter.
When installing the resistor and LED, if the LED does not light, reverse the two wires in case you get it wrong.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
If wired properly, the locow ill move forward when the enginerr's side rail is positive. So if something like an F unit, shoiuld move int he wya the cab is pointed if the right rail is positive. So the + side of an led/resistor for the headlight should connect to the right side pickups.
On a Geep type loco, you'll have to figure out which way it should go based on prototype practice.
LED headlights are kind of not so awesome for DC locos. Either you have to go pretty fast before it lights up, or you put in too small a resistor and it overcurrentz the LED at full throttle. This is where 1.5V bulbs come in handy - you can drop across two diodes to the motor, and wire a 1.5V bulb across them - this give teh bulb 1.4 volts and it will light before the loco even moves.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Cedarwoodron,
To answer Your original question: The center of the bulb with the tiny lead dot is positive, the jacket around the bottom encasing the bulb is negative. Just like an older type Automotive bulb.
Take Care!
Frank
zstripe Cedarwoodron, To answer Your original question: The center of the bulb with the tiny lead dot is positive, the jacket around the bottom encasing the bulb is negative. Just like an older type Automotive bulb. Take Care! Frank
Frank, there is no "positive" or "negative" connection on a bulb. It works equally well either way .... unlike an LED.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Mark R. zstripe Cedarwoodron, To answer Your original question: The center of the bulb with the tiny lead dot is positive, the jacket around the bottom encasing the bulb is negative. Just like an older type Automotive bulb. Take Care! Frank Frank, there is no "positive" or "negative" connection on a bulb. It works equally well either way .... unlike an LED. Mark.
Then why on a clearance/side light is there only one lead coming out of it? That lead is connected to the center of the push turn lock bulb. One of the screw terminals on the base of the light fixture is connected to the side of the base that the bulb casing touches when installed, that connection goes to chassis ground along with all your other accessories, starter,heater,etc. goes to the negative/ground side of battery. So it's pretty safe to say the center of the bulb is positive, casing negative. If it did not mean anything, why would they go through the trouble of making it a standard. Light bulbs in your home/same way, but that is to make sure all the wiring in your house is in phase for alternating current. Black hot center of light bulb, neutral white, base of threads of bulb. I was giving a standard in theory.
Polorized AC plugs same way. Odd looking prong, black hot side, normal prong, neutral white.
I have some small incandescent bulbs where I have soldered a wire to the bottom of the threaded base and another wire to the side of the threaded base. I use this assembly to test for current on the rails. It doesn't matter which wire I touch the wires to the rails. It works either way. So, what's up?
Alton Junction
zstripe If it did not mean anything, why would they go through the trouble of making it a standard.
If it did not mean anything, why would they go through the trouble of making it a standard.
Electrical standards are (mainly) a safety thing. I mean, seriously - you open a box, see three wires and know that the black one is "hot" white is "neutral" and bare (or green, in some cases) is safety-ground. Then you sometimes open a box, and see whatever color the jerk who owned the place before you had ... and you now have red blue and yellow ... and you're looking in there like "oh crap", because you have no idea of what goes where.
Lamps, as Mark stated, are not in themselves polarized. There is no "wrong way" to connect it in a circuit, as opposed to a diode, or electrolytic cap, (etc.) which does have a specific path that electricity must follow.
-Dan
Builder of Bowser steam! Railimages Site
NeO6874 Electrical standards are (mainly) a safety thing. I mean, seriously - you open a box, see three wires and know that the black one is "hot" white is "neutral" and bare (or green, in some cases) is safety-ground. Then you sometimes open a box, and see whatever color the jerk who owned the place before you had ... and you now have red blue and yellow ... and you're looking in there like "oh crap", because you have no idea of what goes where.
Up here in the Chicago area, conduit is required for almost all applications. It is permissible to string wiring for two separate circuits through a single run of conduit. So, sometimes, red is used for the second 'hot' wire, so you will find both red and black wire at the service panel.
Outside of the service panel, it is not uncommon to find other colors wire insulation at light fixtures and wall outlets. Yellow and orange are often used as switch wires and purple or brown are often used as travellers (controllers) between 3-way and 4-way switches.
Alternate colors are allowed where distinctions need to be made, or in cases like the 3 way switches. Where you see black and white wires though, the black should always be the hot side and white the neutral.
In plumbing, red valve handles should indicate hot water, blue for the cold. The jokers who installed my water heater though have the red valve ont he cold water inlet side of the heater and the blue handled one on the hot outlet side. And it WASN'T the previous owner doing a DIY, it was an actual plumber! At least they left all their literature - so I know which plumber NOT to call when I need additional work.
Incandescent bulbs are non polarized. It makes not one bit of difference if you connected + to the base or the side, or even if you feed them AC (they will last longer on DC though, especially when the voltage is kept below their rating). The wiring in a loco is merely a matter of convenience. Since many models emulate the AThearn BB design, the entire chassis., which is normally metal for weight, is connected to one side of the track pickups. Thus a light bulb in a metal holder (like the headlight in the BB locos) only needs one wire connecting it to the other side - BB even skips that wire and uses the clip. Even on the RTR locos witht he circuit board for lighting and decoder connections - there's a wire front and back to one side pickups of each truck, the other side it a short piece of wire with a ring terminal under one of the screws holding the circuit board on. Whole chassis is live, so no need to run wires to each truck on both sides - though they run MUCH better if you do!
I love (not) those LED signals where all of the wires are the same color.
Ugh.
zstripe Mark R. zstripe Cedarwoodron, To answer Your original question: The center of the bulb with the tiny lead dot is positive, the jacket around the bottom encasing the bulb is negative. Just like an older type Automotive bulb. Take Care! Frank Frank, there is no "positive" or "negative" connection on a bulb. It works equally well either way .... unlike an LED. Mark. Then why on a clearance/side light is there only one lead coming out of it? That lead is connected to the center of the push turn lock bulb. One of the screw terminals on the base of the light fixture is connected to the side of the base that the bulb casing touches when installed, that connection goes to chassis ground along with all your other accessories, starter,heater,etc. goes to the negative/ground side of battery. So it's pretty safe to say the center of the bulb is positive, casing negative. If it did not mean anything, why would they go through the trouble of making it a standard. Light bulbs in your home/same way, but that is to make sure all the wiring in your house is in phase for alternating current. Black hot center of light bulb, neutral white, base of threads of bulb. I was giving a standard in theory. Polorized AC plugs same way. Odd looking prong, black hot side, normal prong, neutral white. Take Care! Frank
As others have already pointed out - it does not matter. An automotibe bulb is wired the way it is because the entire car is wired with the body as common ground (negative). You "could" swap the terminals on your car battery and all the lights would still work .... although most other things wouldn't and may even be damaged.
Same goes for the wiring in your house - you could reverse the white and black leads on any light fixture and it will still work just fine. For house wiring, wired properly, a lamp will have the white wire connected to the threads of the bulb with the black wire connected to the post. If it were reversed, you may get a shock if you touch the threads while screwing in a bulb .... you will never touch the post while it is in contact within the socket.
If bulbs were polarized, they should have never worked in one direction in our old engines that just had a bulb mounted in them.
Now toss in a pre-50's car. 6 volt electrical system instead of 12v (now you knwo why all those old articles on runnign trains with car batteries talked about TWO batteries - because one was only 6 volts). And POSITIVE ground.
Vehicles built during the last 10-15years use a computer to illuminate the lamps so hooking up the battery backwards would not turn them on. The center contact is used to ID the positive terminal but the lamp will work ether way. Sometimes the bulb will be ground side switched as the ground is supplied by a wire.
Jim
I'm pretty positive that I know what I'm doing....after a 49 Ford off frame restore, 49 Merc in frame restore, 54 Ford redo, all with 6volt positive ground systems, all wiring replaced because of rubber and cloth rot, but kept 6volt for originality resale purposes. Owning Your own trucks with 4 6volt batteries, 4 12volt batts, with 24 volt starters. Been in a lot more than just playing with trains. My house hasn't burn down yet either, after installing a 250 amp. serv. and rewiring most of it after 35 yrs.
My old line,''I just did not fall off a turnup truck''.
Whether the bulb will light either way is irrelevant, being in phase is.
Darn right, Frank, you tell 'em.
Your in-phase buddy,
zstripe I'm pretty positive that I know what I'm doing....after a 49 Ford off frame restore, 49 Merc in frame restore, 54 Ford redo, all with 6volt positive ground systems, all wiring replaced because of rubber and cloth rot, but kept 6volt for originality resale purposes. Owning Your own trucks with 4 6volt batteries, 4 12volt batts, with 24 volt starters. Been in a lot more than just playing with trains. My house hasn't burn down yet either, after installing a 250 amp. serv. and rewiring most of it after 35 yrs. My old line,''I just did not fall off a turnup truck''. Whether the bulb will light either way is irrelevant, being in phase is. Take Care! Frank
Regardless of your extensive automotive knowledge, bulbs are not polarity / phase sensitive. A bulb is a voltage device and will work equally well on AC, DC forward or DC reverse polarity.
Mark,
Why are light bulbs designed to go in one way, whether they be screw in or twist in? Why don't they tell you, here's the bulb, put it in any way you want. We'll just throw our diagram/schematic out the window. We don't need any standard's.
Well unless you are going to start making left-hand thread bulb sockets, there's only so much you cna do. Now, if you wire a light socket witht he hot wire to the side threads and the neutral to the bottom point - the bulb still works. There is absolutely nothing about an incandescent light bulb that requires polarity or phase to match anything else.
The REASON for it beinf the way it is by stnadrd, with neutral for the threads and hot for the pins, is that this method minimizes shock hazard. That's the only reason things are hooked up liek they are - the NEC establishes baselines for SAFETY reasons, and safety reasons only.
Much the same in cars, if the housing is one side of the circuit, then it's by definition on the ground side - you can change a positive ground system to a negative ground and not need special backwards light bulbs - it's just that the side connected to the car frame is now the negative terminal and the wire clipped on back is now the positive.
If you take a standalone marker light - I used to have a bunch of these, along with batteries, wires, and switches, as one of my 'toys'. The usually have one wire coming out of them, the frame is the other side. Now take some jumper cables and clip them to a car battery. Clip the free positive one to the wire, and the free negative one to the bracket of the lamp - it lights up. Now flip the jumper cables, so the positive one clamps to the bracket and the negative clamps to the wire - hey look, still lights up. Polarity is irrelevant.
Old AC plugs weren;t polarize, both blades were the same size. You can plug things in either way, and they work just the same. The possible danger is when the manufacture made the assumption that the neutral side was same as ground (in the box, it is - they are tied together) and in the metal-cased tool connected the neutral to the case of the tool. Plug the plug in backwards and the tool works, but the case is now hot! Danger! This is why you should not work on electrical things standing barefoot on a cement floor. Touch the hot side and you are connected to ground through your body. Ouch.
zstripe Mark, Why are light bulbs designed to go in one way, whether they be screw in or twist in? Why don't they tell you, here's the bulb, put it in any way you want. We'll just throw our diagram/schematic out the window. We don't need any standard's. Take Care! Frank
Take a desklamp with a non-polarized plug - you can plug it in the wall either way and the bulb still lights up just fine doesn't it ? Sure, there are wiring standards TO the wall plug, but it doesn't matter which way you put the plug in the wall. Whether your vehicle is negative ground or positive ground, the same bulb still works just fine in the same socket. We're not discussing electrical wiring standards, we're talking about the BULBS.
And yes, you CAN put the bulb in any way you want. As long as it sees the proper voltage it WILL light.
Jeez, I'm saying the same darn thing You Guys are saying. But My way. I must be from a different planet.
Senseless discussion.
No, this is a shocking discussion
It still doesn't explain the feeling I get when I operate my bathtub layout.
Rich,
I heard that you will get a more memorable feeling in a jacuzzi layout, with all those bubble's.
Frankie
zstripeI heard that you will get a more memorable feeling in a jacuzzi layout, with all those bubble's.
You haven't tried lighting one of those bubbles, have you?
richhotrain It still doesn't explain the feeling I get when I operate my bathtub layout. Rich
It could be too much bath salts, remember, everything in moderation