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Dangling resistors?

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Dangling resistors?
Posted by BATMAN on Monday, February 05, 2018 2:01 PM

I was thinking of using caulk to stick some 1/4 watt resistors to the plastic on the underside of my RH. Then thinking they need to dissipate heat, not such a good idea? How should I mount these things and to what? I will probably have seven resistors to mount somewhere. I don't want to leave them dangling mid-air like have seen some others doing, suggestions. 

Brent

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Posted by DigitalGriffin on Monday, February 05, 2018 2:47 PM

Underside of your RH?

If you are running them below 80% of their design limit, you should be fine.

For 1/4 watt resistors thats .2 Watts

For 1/2 watt resistors thats .4 Watts

The air should be more than enough to cool them and have a long life.   The only thing I would be worried about is shorts.

Don - Specializing in layout DC->DCC conversions

Modeling C&O transition era and steel industries There's Nothing Like Big Steam!

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Posted by SpaceMouse on Monday, February 05, 2018 2:50 PM

How about gluing the ends between two popsickle sticks and gluing that to the RH.

Chip

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Posted by rrinker on Monday, February 05, 2018 3:03 PM

I'd leave them sticking up by their leads, in open air. They shouldn;t get anywhere near warm enough to melt any plastic parts, but I wouldn;t stick them in caulk either. Caulk the leads to a support beam and leave the resistor body float free.

                                       --Randy

 


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Posted by gregc on Monday, February 05, 2018 3:05 PM

what is RH?

greg - Philadelphia & Reading / Reading

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Posted by BATMAN on Monday, February 05, 2018 3:09 PM

RH= Roundhouse

Brent

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Posted by SpaceMouse on Monday, February 05, 2018 3:09 PM

gregc
what is RH?

I assumed Roundhouse.

Chip

"Rock Ridge and Rock Ridge Lumber are names that really stand for something" --Randal "Rock" Ridge, Mayor and Founder

"Mining is the very foundation of a free America." --Stanley "Stone" Ridge

"Give me Apathy, or give me something else."--Carlton Ridge, aka "The Cat"

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Posted by DigitalGriffin on Monday, February 05, 2018 4:14 PM

Oh this is lighting for a round house?!?

I fed two brass wires between the trusses of two adjoining timber frames (part #14)  One was positive, the other negative.  I then dropped LED between the two wires with slightly curved ends.  I fluxed and soldered them in place.

18 stalls @ 7 ma  x 2 (rows) = .252 amps

5-3.5 = 1.5V

1.5 = .252 amps R

R = 5.95 Ohms

I can go with 6.8 or 5.6 (common available values).  I went with 5.6

Power across resistor = .40 Watts.  If you are worried that is too much, just use two 2.7 + 3.3 Ohm resistors in series.  Half the LEDs would have to burn out before I started sweating about current.  And considering they typically have a life of 20,000 hours, I don't have to worry that much.  I hid the resistor on the lead + wire heat shrinking the exposed metal.

I just wish someone made light hats for T3 LEDs  Trying to get the wires through the holes and not short is a major pain.

Don - Specializing in layout DC->DCC conversions

Modeling C&O transition era and steel industries There's Nothing Like Big Steam!

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Posted by BATMAN on Monday, February 05, 2018 4:30 PM

This is what I get using the array wizard.

http://led.linear1.org/led.wiz

Solution 0: 4 x 8 array uses 3

2 LEDs exactly

+15V
+      + R = 120 ohms
+      + R = 120 ohms
+      + R = 120 ohms
+      + R = 120 ohms
     R = 120 ohms
+      + R = 120 ohms
+      + R = 120 ohms
+      + R = 120 ohms

The wizard says: In solution 0:

  • each 120 ohm resistor dissipates 48 mW
  • the wizard thinks 1/4W resistors are fine for your application Help
  • together, all resistors dissipate 384 mW
  • together, the diodes dissipate 2048 mW
  • total power dissipated by the array is 2432 mW
  • the array draws current of 160 mA from the source.

Brent

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Posted by DigitalGriffin on Monday, February 05, 2018 6:43 PM

well

15 - (3.5 * 4) = 1 Volt

If you run at 7ma

1 = .007 R

R = 142 Ohms

V*V / R = (1 * 1) / 142  = .007  Watts which is negligable.

In otherwords, you can work with a lot less resistors if 15 Volts is your source and you do 4 in a row.  If you want I can draw you a diagram and I won't be insulted if you consult with someone else.

Using L7805 to step you down to 5 Volts would be a better way to go though in my opinion.  They are <$1 each on amazon

Don - Specializing in layout DC->DCC conversions

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Posted by Atchee on Monday, February 05, 2018 7:25 PM

Supporting resistors strictly by the leads is not an uncommon practice.  Prior to the use of printed circuit boards in radio and TV, components were installed between "tag strips", a single or multiple strip of terminals to each of which multiple components were soldered, and hung in free air between them.  Fairly large resistors were very common and only larger capacitors were mounted to some kind of support.  Up until the pretty much universal practice of surface mounted parts some resistors were mounted proud of circuit boards to provide a bit of extra cooling.  In heavy duty stuff some still are.

If you have enough vibration to break the leads of a "hanging" resistor you will have other issues as well.

 

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Posted by BATMAN on Tuesday, February 06, 2018 12:17 PM

Don 

Electronics are not my strong suit and I would appreciate a schematic. Basically 7 rows x 4lights each is what I would like. I suppose 4 rows of 7 lights may also work.

I have the light covers (hats?) and wire from Ngineering along with a bunch of other stuff. I have warm white 3.0- 3.2v/ 20ma LEDs and a bunch of these I got for $1.00 each.

https://www.amazon.com/Control-adjustable-regulator-Step-down-Regulator/dp/B01ARR8NNG

My transformers in the junk box read about 15.9 v. I also have a large collection of wall warts I have kept from everything we have thrown out over the years.

The RH sits on foam and I was planning to have the resisters under the floor and run a wire up each post at the front. I will cut the appropriately sized hole in the foam so they can breathe.

Much appreciated, thanks.

Brent

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Posted by rrinker on Tuesday, February 06, 2018 12:27 PM

 You already did. The LED array wizard gives your answer. But run it again and put somethign less than the peak LED current in there - say 10ma. It's the same circuit you posted above, but with 270 ohm resistors instead. The wizard shows the schematic and everything.

                         --Randy


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Posted by richg1998 on Tuesday, February 06, 2018 12:39 PM

I ran 1k resistors with 9ma. Bonded then with caulk some years ago. Not a big deal.

Rich

N

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Posted by DigitalGriffin on Tuesday, February 06, 2018 1:39 PM

BATMAN

Don 

Electronics are not my strong suit and I would appreciate a schematic. Basically 7 rows x 4lights each is what I would like. I suppose 4 rows of 7 lights may also work.

I have the light covers (hats?) and wire from Ngineering along with a bunch of other stuff. I have warm white 3.0- 3.2v/ 20ma LEDs and a bunch of these I got for $1.00 each.

https://www.amazon.com/Control-adjustable-regulator-Step-down-Regulator/dp/B01ARR8NNG

My transformers in the junk box read about 15.9 v. I also have a large collection of wall warts I have kept from everything we have thrown out over the years.

The RH sits on foam and I was planning to have the resisters under the floor and run a wire up each post at the front. I will cut the appropriately sized hole in the foam so they can breathe.

Much appreciated, thanks.

 



Randy is right, you are on the right track with your diagram.

I'm assuming you have 7 stalls, that are four lights deep.  That sounds like a lot.  Have you set up a mock setting for 1 stall yet?  Two deep @ 7 ma was plenty for mine.  4 deep ( every stall) every 10 degrees @ 20ma sounds like a lot of light.  10ma is enough to shine through plastic walls that are painted.

 

4 * 3.1V = 12.4V

15 - 12.4 = 2.6V

V = IR

2.6 = I * 120 Ohms

2.6 / 120 = .021 OR 21 ma...A little on the HOT side.  You'll shorten the LEDs life

V*V / R = power = .021 Watts...so < 10% of a 1/4 watt resistor max power...so your resistor is safe.

Mine was a much simpler arrangement of 2 rows of brass wire pairs (+5V / ground) in the shape of a U with single resistor on the end of the lead wires.  Like I said, I wasn't worried about LED burnout because with 36 bulbs, and 7ma, I could lose half, and still be within current limits for each one. 

 

Don - Specializing in layout DC->DCC conversions

Modeling C&O transition era and steel industries There's Nothing Like Big Steam!

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Posted by BATMAN on Tuesday, February 06, 2018 3:36 PM

Thanks, guys.

The number of bulbs is a lot I agree but after looking at an awful lot of lighted roundhouses, I like the very dull but well covered look. I am probably biting off more than I can chew but it will be nice if I can also get some handheld work lights in there as well as a welder. We'll see.Laugh

Brent

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Posted by zstripe on Tuesday, February 06, 2018 3:41 PM

Brent,

Just about all the structures I make I use 1/16'' hardened brass rod...I buy it in the 36'' length and cut to fit. It is used as a bus to hold the lights/Led's plus the resistors...that way all I need is two wires to feed it down through the layout. Just about all My structures are removeable, especially the roofs. This overpass you can see the brass bus. The two long brass 1/8'' rods, actually support the overpass down ramp that slide into a sleeve bus that also supplys voltage to the Led lights on the ramp, eliminating all wires hanging down. On the long truck dock..the brass rods go through the lattice trusses to support the incandesant lights and support the roof, which is removeable in two sections. Two wires go down a 1/8'' tube through the layout to a barrier terminal stripe underneath that go to a centralized control panel where the electronic's are for all the structures.

All photos may be clicked on for a larger view.

Take Care! Big Smile

Frank

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Posted by BATMAN on Wednesday, February 07, 2018 3:33 PM

Hi Frank.

I hope mine turns out half as good. I am going to take a crack with Ngineerings #38 magnet wire and their lampshades with a LED hanging down from the ceiling. Very tiny stuff to work with, however just doing a few a day should be okay.

SHHHHHH! I have swiped some of my wifes microsurgery tools to hold everything.Whistling

Wish me luck.Laugh

Brent

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Posted by zstripe on Wednesday, February 07, 2018 5:10 PM

Brent,

Just remember You Do Not have to strip the enamel from the magnet wire before soldering.....do a mechanical wrap of the wire, (wrap around a couple times to what You are soldering to) the rosin core solder will melt the enamel when soldering. I use silver bearing solder paste and flux is part of the paste...works every time. I use a lot of magnet wire lighting.

Take Your time........Good Luck! Big Smile

Frank

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Posted by graymatter on Wednesday, February 07, 2018 7:09 PM

Just to add to the "current"question....If the prototype is a gas or flame and not incandescent lighting you can use a circuit to cause the light to flicker. Similar to those LED candels. I am not sure the electrical supply was as well regulated as it is today. so some flickering might be era correct.

My 2 Cents

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Posted by graymatter on Wednesday, February 07, 2018 7:26 PM

Batman

Is a 5mm LED to big? 

5mm = 0.2 inch x 87 = 17" light bulb?

If you go for the flicker its about 59 cents for a led that flickers.

 

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Posted by BATMAN on Wednesday, February 07, 2018 7:34 PM

The roundhouse I am trying to emulate got electricity in 1897. I doubt it was reliable and I read the light was so dim they still used lanterns with reflectors for up close lighting. 

How do you tell the + & - on these LEDs? I haven't looked yet. I do have some good equipment to hold them as long as I don't lose them first.Laugh

Brent

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Posted by Overmod on Wednesday, February 07, 2018 7:48 PM

BATMAN
The roundhouse I am trying to emulate got electricity in 1897. I doubt it was reliable and I read the light was so dim they still used lanterns with reflectors for up close lighting. 

By 1897 carbon-filament lighting up to roughly the output of a modern 40-watt bulb had been long perfected, as had automatic-regulating arcs and a range of high-intensity lights using the general principle of the incandescent thorium mantle -- limelights are one example.

To modern eyes this is toward the red end of the spectrum and dim, but it was bright to them.  Keep in mind that the 'lanterns' might be Argand lamps with large reflectors, like some contemporary locomotive headlights, much brighter and whiter than you'd think, and just like dynamo-fed carbon bulbs, very little visible variation or flicker.

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Posted by graymatter on Wednesday, February 07, 2018 8:21 PM
Image result for anode of led
 Click gray box for link to LED polarity
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Posted by BATMAN on Wednesday, February 07, 2018 9:04 PM

I think mine are nano's. Suppose to be colour coded. I have red/green issues, could be interesting.Laugh

Brent

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Posted by zstripe on Thursday, February 08, 2018 5:03 AM

Brent,

I'm holding a Nano chip in My paw in this pic'......I also used them in some scratch built railroad yard lights and street lights. The round lense looking thingy inside the brass lampshades are Athearn BB F7 porthole lenses that I happend to have a bunch of....... Red + Anode, Green - Cathode.......

  

You may click on pic's for a larger view:

 

Take Care! Big Smile

Frank

 

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Posted by rrinker on Thursday, February 08, 2018 6:47 AM

 If you have trouble distinguishing red and green, build yourself a little test jig. 9V batter and a 1K resistor. Touch the LED wires to the free end of the resistor and free battery terminal (the other side of the resistors goes to the other battery terminal, if it wasn't obvious). If it lights up, great, the LED lead on the + side of the battery is the + wire. If not, reverse the LED wires. If it still doesn;t light up, something's broken, but if it didn;t light up the first time, it should now, and again you have identified which wire is the +. If you are not going to immediately solder the LED into the circuit, you can do something like put a loop in the very end of one wire to mark it for later.

                                         --Randy

 


Modeling the Reading Railroad in the 1950's

 

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Posted by DigitalGriffin on Thursday, February 08, 2018 9:16 AM

T3 is 3mm or about 10" in HO.  Not much better but still much closer.  A 10" globe cover is almost believable.

Don - Specializing in layout DC->DCC conversions

Modeling C&O transition era and steel industries There's Nothing Like Big Steam!

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Posted by DigitalGriffin on Thursday, February 08, 2018 9:19 AM

BATMAN

The roundhouse I am trying to emulate got electricity in 1897. I doubt it was reliable and I read the light was so dim they still used lanterns with reflectors for up close lighting. 

How do you tell the + & - on these LEDs? I haven't looked yet. I do have some good equipment to hold them as long as I don't lose them first.Laugh

 



Back in the day, Edison bulbs were rarely over 30 Watts.  They were just carbon film over a thin cotton strand and not very efficient.  It wasn't till later they started using Tungston.

Arc lamps were very rarely used as they emitted Ozone and hazardous UV light.

Doing a google search, I found a 40 watt edison which put out 230 lumens.  A 40 watt incandecent puts out up to 500.  A 60 Watt, over 800 lumens.  So a big difference. 

The + leg is usually a tad longer.  Also for SMD LEDs (the super tiny ones without metal leads) the + pad is marked with a +, or a white mark, or a slightly thicker soldering pad.  Do not leave your soldering iron on the SMD leds for more than 1 second.  What I like to do is hold the wire to the soldering iron which has solder on it and touch them at the same time onto the SMD.  That way the solder bead on the wire is still molten when it touches, requiring less time for the iron to touch.

When wiring USUALLY White / Red are usually hot (Positive) and Black and Green neutral (Ground or negative).  

Remember it this way, It's White HOT or Red HOT.  HOT meaning it has voltage.  GReen = GRound

Don - Specializing in layout DC->DCC conversions

Modeling C&O transition era and steel industries There's Nothing Like Big Steam!

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Posted by BATMAN on Thursday, February 08, 2018 1:04 PM

Thanks for all the tips guys. The light shades are 24" HO and you can see how small that little yellow LED is. The #11 is in case I want to end the torture.Laugh

  

 

Brent

It's not the age honey, it's the mileage.

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