Hello ! Help needed regarding model railway lighting ?.

[Chris Uddin]

Hello guys, hi everyone that's been helping me, here in the UK It's 02:58am thursday, I've been trying a few resistors which I received today now I went through a lot of Brown carbon film ranging from CR25 1/4W 1R - through to CR25 1/4W 2K2 resistors, 1 amp 1000 v rectifier diode 1N4007 a couple of green wirewound axial resistors 0.R & 150R 2.5W and I'm still yet to go through the mountains of blue 1/4W metal film resistors 1% assortment kit of 400 and a series.

I've come to the conclusion that the lower you go down in resistor the dimmer the led lights would go, I thought that the 1 amp 1000 v rectifier diode 1N4007 came closest to the brightness that I wanted and this was done with the lights being in one single strip, now I have cut the lights into 5 blocks of 3 and I will try the resistors again to see whether it makes any difference and bear in mind at this stage I've not yet used the bridge rectifier which I'm still waiting for, so I don't know whether that will reduce some of the brightness as well as the resistor, as soon as I have do some things later today I will hopefully post some pictures and let you know how things have going, it will probably be my daytime but your night-time so please forgive me if I'm disturbing you wherever you are in the world and I look forward to hearing from you all when I'm able to post something, all the best guys, cheers, Chris.

[RJSV]

Looking scrambled to me.
   Any clear result, trying the (repeated) pleas to include the protection, of a bridge.  Maybe stay on that.  That protects the strip you bought.
Maybe, resist the temptation, to rush off and 'test' like 190 different resistors...meanwhile, all of a sudden, discussion shifts to...the diode.  I thought, it was decided to use the bridge.  Did you order just that?
  That bridge is protecting your stuff.
  And, waters getting so muddy: Are you still trying to use that original, strip?  That was damaged, or operating incorrect, got too hot, right ?
Things just seem to go round and round.
   Then, mid-sentence, it's 'DCC', all of a sudden.
   The advice line, was, to protect your stuff, from reverse voltage being applied.  Damage can happen, no matter how many other things you try.
Protect first. Change, like ONE thing, at a time.
    It's also very likely, your eye can't distinguish, between 500 ohms and 580 ohms brightness, anyway.
   Why even test, if that, original, strip is still in the mix.
Did that ever 'recover', in subsequent tests, without changing 3 other things, plus some other mid-sentence 'mention', of how a diode, maybe causing 5.6 amps (whatever that meant).
Thanks

[MarkF]

 

I've come to the conclusion that the lower you go down in resistor the dimmer the led lights would go, I thought that the 1 amp 1000 v rectifier diode 1N4007 came closest to the brightness that I wanted and this was done with the lights being in one single strip, now I have cut the lights into 5 blocks of 3 and I will try the resistors again to see whether it makes any difference and bear in mind at this stage I've not yet used the bridge rectifier

I'm confused.
You say the lower the resistor value the dimmmer the LEDs are.  That just can't be. 
You must be doing something else to see that effect.
Remember, lower the resistance is like approaching a short circuit (i.e. not having a resistor).
Are you reading the resistor values correctly?  Measure them.  Set your meter to the 200 or 2000 range.


As far as a diode or a bridge, they only come into play when you get to the point of attaching the LEDs to your DCC system.  With your Combi, the diodes are only going to drop the voltage a little (up to 1V with a bridge, less with the diode).  It's like turning the Combi down a little.
The bridge will be like having two diodes in series if you want to see the result before getting a bridge.

Your goal is to find a resistor value that gives you the desired brightness with the Combi at max (i.e. what the LEDs will see using DCC).  You don't need to try all your resistor values.  Just a few (1K, 470, 100, 47, 10) to get in the ball park.  I'm going to guess it will be 22 ohms with the 18 LED strip.  The second goal (and most important) is to find a resistor value that gives a max voltage of 12V right at the LED strip input.

Set your Combi to max and try resistors to have less than or equal to 12V at the LEDs (between the resistor and LEDs).  Then try different combinations of LED groups to get the effect and voltage at strip.  With fewer groups of LEDs, the resistor value will need to be increased.  You want to see if you can find an acceptable brightness in the coach with fewer groups with a higher resistor.

[RJSV]

Looking better, sorry if I 'ranted' a bit.  But here is some helpful comments:
   Our 'language' in U.S. is imperfect, as we say "Is it getting POWER ?...", but meaning is most often answered, using Voltage, like:
   "Yeah, it's getting 5.3 Volts."
So; it 'reads' a bit smoother, to mention units, which get switched, naturally, to Volts (not Watts).  Plus, common mention leaves out the meter range.
That means, a person more likely, instead of a string of unanchored digits, with Voltmeter set to '30 volts' range:.    '30.   5.3.  0.3',
better to say " yeah, I'm getting 5.3 volts, on LED, so it's powered...".
Very confusing, at first, but that's the real world, imperfect.
    I'm thinking, regarding setting your levels, at some point you will be trying things, using TRACKS and a RR car, (with the combi first), so the carriage orientation could be reversed...Diode protects against that...
But a (single ) diode won't power your car lights, both directions, of car, or both halves of +/- DCC.
Perhaps, later, you might be forced to replace the windows, in each car. But one thought, doing THAT allows you to place, a RED or BLUE window...
Maybe an 'armoured' PAYROLL CAR !

    You've got a great project, perhaps publish your own article, later, if there is some good Model Lovers mag.
-- Rick B.

[MarkF]

Looking better, sorry if I 'ranted' a bit.  But here is some helpful comments:
   Our 'language' in U.S. is imperfect, as we say "Is it getting POWER ?...", but meaning is most often answered, using Voltage, like:
   "Yeah, it's getting 5.3 Volts."
So; it 'reads' a bit smoother, to mention units, which get switched, naturally, to Volts (not Watts).  Plus, common mention leaves out the meter range.
That means, a person more likely, instead of a string of unanchored digits, with Voltmeter set to '30 volts' range:.    '30.   5.3.  0.3',
better to say " yeah, I'm getting 5.3 volts, on LED, so it's powered...".
Very confusing, at first, but that's the real world, imperfect.

My understanding is that the OP has very little, to no, technical knowledge.  So, you HAVE to read between the lines.
You can see that when the OP began using his meter, we got some really strange comments.  But he got there in the end. 
Right now I'm not sure he knows how to read the resistor color codes.
With a little more guidance, he will get the results he wants.

The key here is asking the right questions so we understand what sometimes seems strange. 
Several times I've missed the big picture here by assuming what seems obvious to me.

As to the bridge which seems to be a big issue for you, it all comes down to where he is going to run the coaches.  If it's DCC only, then a diode will be sufficient.  If in DCC analog mode or strictly DC (his Combi), then a bridge will be required.  Something I haven't ask.  Using a bridge will give him the most flexibility.
I've been a little too focused on finding the lowest cost solution.