LED 3 Volt DC Lighting Issues...I'm Stumped & Need Your Help!

Sounds like you are wiring in series. 

If your wiring in series you're exceeding the transformers amperage.  If wiring in parallel you are exceeding the voltage rating of the transformer.  

The experts will chime in, but am pretty sure you need 100mA for each light, or 1600mA for all of them.  A 3vdc 2A(2000mA) wall wart should do the trick, or if you have accessory power/track power available use an ac to dc step down converter and adjust to 3vdc out to lights.  Many ways to power your lights with small investment.

Train Nut posted:

If your wiring in series you're exceeding the transformers amperage.  If wiring in parallel you are exceeding the voltage rating of the transformer.  

Take that and reverse it.  

It sounds like the solution is a bigger transformer.  off the auction site you can likely find a 3VDC 2Amp wall pack for about 5 bucks or so ordered from china.  Another option if you have some other voltage of transformer already lying around is to wire some number of lamp posts in series.  Ex. 2 posts in series could be run at 6V, three at 9V, 4 at 12V and so on.  

In addition, the listing for the lamp post says they will work on AC as well as DC, so you could use a typical train transformer here.  It may be worth checking if the posts actually have a rectifier diode in them, as if they do not it may shorten their life running on AC.  In either case, it may be worth while to add a 1n4001 diode to each lamp for a penny each.  

If it was my layout, I would run four sets of four lights in series with a 12VDC supply.  You can use an ATX computer power supply that can typically provide 12VDC at 15 amps or more and can be bought new for under $20, or used for about $5.  

Thanks for the responses so far. I did try wiring in both parallel and in a line and the lampposts still dimmed with each added lamppost (3 lampposts and more and they would not even light up). It did not seem to matter what way I wired them up. The end result was the same.

Aside from the very basic info from the Chinese vendor on milliamps required, it would have been difficult to understand if the milliamps requirement was for one light or more.

So, if it does matter how many lamps you add up...I just need to add together the milliamps per light to determine the correct amp/milliamp transformer requirements needed, correct?

If that is the case, then my questions are two fold:

1) If I wire the lights in a series, if each lamppost works on 3 volts, then the required voltage would equal 3 volts X the amount of lights I have correct? If that were the case, I am assuming I would need one 12 volt transformer for every 4 lampposts, correct?

2) If I get a higher amperage 3 volt transformer, there are a few 1000 mA plus in transformers out there and even a 2000mA transformer that I see...but they all have a coaxle style wire, which has a pain in the but braided conductor outer sheathing wrapped around a solid wire core. Has anyone seen a 3 volt 2000mA transformers with two wire leads instead of some sort of a jack for connections?

And another question: Since nearly everything else I have is AC, have I just been very fortunate to not have the dim lights problem by wiring lights together (always in parallel) because the ZW and R transformers I use have more than enough amps to keep everything lit? I always wondered about that as the lights only got brighter with higher voltage. I never thought about the amp needs before as well. I did find out that the trains love the 14 gauge track supply wire I soldered directly to the track. Some trains run similar but others fly where once they strained on a given voltage. I guess there is more to electrical wiring than meets the eye!

I could have missed in it in the lamp spec's but I didn't see any mention of LEDs ?  The description says "clear mini bulbs" ?   100 ma would be a lot for 3 LEDs.    In any case, the folks are correct, seems like your power supply is too small and  can't provide the amps.  As a test, set your AC train transformer to 3 volts and start adding the lamp sets.  You should see brightness unchanged as the lamp sets are added.

The specs. say mini-bulb, AC or DC. A bulb is going to draw about five times the current as a LED. So like everyone said, larger power supply.

One of your lamps looks very similar to Lemax 44184,   Here's the Amazon page:   https://www.amazon.com/Lemax-C...-Piece/dp/B004JYAQX4

Are you sure these are LEDs as opposed to incandescent mini-bulbs?  Anyway, doesn't matter what's under-the-hood, you need more power!

As the other guys are suggesting, your 3V 0.2A (200mA) transformer is grossly under-sized for the matter at hand!  Your adapter puts out only 3V x 0.2A = 0.6 Watts.  Volts x Amps = Watts.   And at $11, that's a whopping $18 per Watt.   For wall-warts, adapters, or whatever you call these widgets, you should be paying more like 10 cents per Watt!

Each lamp post apparently requires 3V x 0.1A (100mA) = 0.3 Watts.   You have 16 posts.  So if the 100 mA is referring to the entire post, you need at least a 5 Watt adapter.  Actually, it's not clear to me if the 100 mA refers to each individual bulb in the lamp post or the entire lamp post;  that is, there are 6 wires to connect so each bulb appears to come out separately. 

Anyway, what I'd do is get a ~$3 DC-output wall-wart/adapter with at least 15 Watts capability and follow it with a ~$3 DC-to-DC adjustable converter.

For example, on eBay with free shipping from Asia:

So that's 12V x 2 Amps = 24 Watts... or roughly 10 cents per Watt.  Note you can buy a female screw-terminal adapter to convert the barrel-coax connector to wires without soldering or splicing into the wall-wart wiring.

Then you follow this with a DC-to-DC converter module to convert the 12V to 3V.  For example, here's one that even has a built-in digital voltmeter so you can mess around with 2.9V, 3.0V, 3.1V, etc. to tune the brightness to your liking.  Note that this particular module has screw-terminal inputs and outputs so no-soldering required.

So together it might looking something like this:

Or, if you have your own voltmeter and/or don't mind soldering wires to modules, you can save a buck and get a DC-to-DC converter module that doesn't have a built-in voltmeter or doesn't have screw-terminal connectors.

Thanks again for the info so far. I guess I assumed incorrectly that these are LEDs. I just put one lamp to an AC transformer and it did light (quite brightly mind you as I don't think the transformers go lower than 6 volts). I paid a like $60.00 for 20 lights. I hope that they don't burn out any time soon as taking the sheathing off these tiny wires and soldering them together is a bear. That being said and being that I can likely get away with a standard train transformer I am going to first finish soldering the remaining lamppost connections, wire everything together, install one resistor (I don't think I need one for every lamppost) and then connect it to a transformer again to see how it works. I will keep everyone posted...

I would advise being careful to not put too much voltage out to your lights. If 3vdc/ac is recommended then I would limit the voltage to as close to that as possible.  I’m pretty sure the reason your lights were bright hooked to the xfrmr was over voltage.  Others should chime in if this is overly cautious.

BTW Here are a couple of the cheapy converters Stan mentioned, with no meter and requiring soldered wires.  They work perfectly.

What size resistors did they send you and did you solder them in yet, they should allow you to run them at over 3v DC???

Marty

Train Nut posted:

If your wiring in series you're exceeding the transformers amperage.  If wiring in parallel you are exceeding the voltage rating of the transformer.  

If your wiring in series you're exceeding the transformers VOLTAGE.  If wiring in parallel you are exceeding the AMPERAGE rating of the transformer.

Lou N (Chiming in)

TedW posted:

I would advise being careful to not put too much voltage out to your lights. If 3vdc/ac is recommended then I would limit the voltage to as close to that as possible.  I’m pretty sure the reason your lights were bright hooked to the xfrmr was over voltage.  Others should chime in if this is overly cautious.

 

 

You are not being overly cautious.  Life expectancy of incandescent bulbs is proportional to the 16th power of the overvoltage.  The graph is almost a straight line down.

Lou N (chiming in again)

Do not exceed 3V ac/dc on these lamps.  Doing so will shorten the life of the bulbs substantially as stated above.   The lamps are designed to be wired in parallel (i.e. 3 v on each lamp).

Well I have worked nearly 10 hours today on this project alone. I have all the lights wires in parallel. Basically I have 4 sets of 4 lamps wires together at a few different connection points. Isoldered on one resistor on one of the two wires leads feeding all the lampposts between the transformer and the first connection...and all lampposts are dark.

I think I am done and out of inspiration today. What are your thoughts? Before I tied all the lamppost connectors together I did test a few of the groups of 4 that were wired together and they did light up bright using a simple transformer connection and no resistor. Do I need to install one resistor before each set of 4 lamps tied together or is a single middle-of-the-line resistor needed? Do I need a resistor on both feeder wires, or will just the one be OK (I did attempt t connect the wires reversed around on the transformer terminals to see if it made a difference, and I got the same results)? Maybe it is a math thing...! I have not tried to run all the lights without the resistor though. Maybe that may be my last attempt for the day,

As long as your input voltage does not exceed 3 volts you don't need any resistors.

The ATX computer power supply has a 2 wire 3 vdc tap.

One last post for the night on this. I cut out the part of the wire that had the resistor in it and viola!

The two-bulb downwards-pointing lampposts are in the front and rear of the lower series of station platforms. The 3 globe lampposts are in the front and rear of the upper station platforms.

I have to be very careful using them for now, as this picture is at minimum power on a ZW transformer. What I need is that variable voltage board #TEDW mentioned above. I've seen that board before, but never thought I would be needing it. I'll have to find a place to conceal it! Hopefully that will work better than the resistor did...and it is fairly cheap.

Anyways, the lights are quite nice and I did wire everything properly to begin with. I am disappointed they are not LEDs, but if they last for years (not like I can just order up replacement parts), then I will be happy. I do have a couple of spare lamps if one ever does burn out (entire lamppost change out). Thanks again for everyone's input.

FWIW, I think you would be better off with Stan’s version.  The screw down connectors and included volt meter are worth the extra dollar or so, in my opinion.  I bought a pocket full of digital meters for cheap and added them to my modules.  Your lighting really does look nice, good job.

shorling posted:

As long as your input voltage does not exceed 3 volts you don't need any resistors.

That depends on the specific LED's, and having no balancing resistors may yield unsatisfactory results.  Unless all the LED's are well matched, you could get bright and dim LED's.  The operating voltage of different brands can very. I like to operate LED's like this in parallel with a higher voltage and a balancing resistor, makes it a lot easier to get consistent results.  Even running in parallel, a series resistor for each bulb will allow you to get far more consistent results than trying to tweak the voltage to the exact requirements.

Here's a typical voltage vs current curve for white LED's, notice the steep rise in current for a very small voltage change.

gunrunnerjohn posted:

shorling posted:

As long as your input voltage does not exceed 3 volts you don't need any resistors.

That depends on the specific LED's, and having no balancing resistors may yield unsatisfactory results.  Unless all the LED's are well matched, you could get bright and dim LED's.  The operating voltage of different brands can very. I like to operate LED's like this in parallel with a higher voltage and a balancing resistor, makes it a lot easier to get consistent results.  Even running in parallel, a series resistor for each bulb will allow you to get far more consistent results than trying to tweak the voltage to the exact requirements.

Here's a typical voltage vs current curve for white LED's, notice the steep rise in current for a very small voltage change.

GRJ,  I agree with you 100% however the tech spec's for these lamps don't make any reference to LEDs, the opposite in fact.  The spec's call for dropping resistors if voltages greater than 3 volts are used.  If using 3 volts, dropping resistors might be useful for light balancing or life extension.

Hi again. #STAN2004, I like the looks of the DC converter board with the built in voltmeter. However, now that I realize the lights are AC, I'd prefer to use one of my many AC transformers to power it rather than buy another wall wart.  That being said, would you suggest a product like this AC input to DC output converter to use in conjunction with the board you mentioned? Or do you think it is best to but a wall wart with an adapter for wire input and use that with the board you suggested, as the wall wart has already converted the voltage to DC? Please advise me and thank you.

https://www.ebay.com/itm/AC-DC...STh6Go_DgepN8vBGI0VQ

Definitely do NOT get that particular module.  It does indeed perform the AC-to-DC conversion that you want, but it uses an older technology which is inefficient - great for keeping your train room warm in the winter (note sarcasm!).

Anyway, if you want to use AC voltage from a train transformer...such as the 14-16V AC Accessory output, or even a main track output at 18V AC (or whatever), consider the following:

On the left is an AC-to-DC converter module that I use myself (and other guys on OGR have posted using this too).  It has screw-terminal inputs so no soldering required.  You use a tiny screwdriver to adjust the output voltage to 3.0V DC.  I am not aware of any economical AC-to-DC converters that have a built-in voltmeter.  But if you don't have a voltmeter handy, you can buy a 2-wire voltmeter that you connect "in parallel" with your lamp-posts (in other words, the voltmeter is wired up as if it was another lamp-post).  This would then indicate the voltage out of the converter.  In the photo I show a fancier meter that reads both Voltage and Current (Amps) but I don't think you need that capability.  Instead on the right is a low-cost voltage-only meter that you could use to set the voltage to 3.0 (or 2.8, 2.9, 3.1, 3.2 if you want to adjust brightness).  Obviously do this adjustment BEFORE you hook up your lamp-posts since we don't know what the converter module output voltage is set-to when you get it!  If this approach makes sense but you need an exact wiring hookup diagram, I can draw one up for you.

Note that eBay direct links are not allowed per OGR terms-of-use....hence I don't provide the links as I've had posts where I've included them deleted by the moderators.

Hello all. I waited a few weeks for new circuit boards to convert the AC (or DC) transformer voltage down to 3 volts DC (or less). From what I have read, the input voltage must be 3 volts above the output voltage for the item to work correctly...which won't be a problem for me. It has a nice LED output display so I don't have to pull out the ol' voltmeter and has an easy-to-adjust rotary knob. It may throw off a little heat...but I don't think it will be a problem. I am mounting it to some wood by my transformers. If heat is a problem, I will report back here.

As I have found out, my lights are non-LED...but many LED lights run on 3 volts too...so this item may help others out as well. Happy railroading out there!

https://www.ebay.com/itm/LM317...a:g:LzcAAOSwWnFWClIJ

At 3 volts out on track power, it's likely to throw out a LOT of heat, and certainly if you power some incandescent bulbs off it!

A far better choice would be this one, eBay: 391650745066, and it's cheaper as well.

Just curious John, how do you know that one will dissipate less heat? What's the tell tale in those pics, or are you familiar with both products? Trying to learn, here.....

George, the LM317 is a linear regulator, so any voltage differential between the rectified supply voltage and the output voltage is turned into heat.  Given 18 volts track voltage, the rectified and filtered DC voltage will be around 25 volts, so that gives you 22 volts to lose before you supply the load.  Let's say, for argument's sake, your load is 200ma, that's 4.4 watts of power you're pushing out, that's all being turned into heat in that LM317.

Contrast that with the switching regulator, let's assume 90% efficiency, they quote 96%, but that's with more voltage out.  In this case, instead of 4.4 watts, we're dissipating .4 watts in the regulator, you'll hardly feel the temperature change.

Thanks John, that helped. I didn't realize the LM317 was a linear regulator. So is the output of the switcher filtered DC or high freq DC pulses? No reason to ask other than just curiosity.

Pure DC, it's filtered before going to the output.  Since it's a high frequency, it also takes a much small filter to do the job.

Hi again everyone. A quick update. The below part I ordered and just installed smoked out and had a split-second flare up below the small capacitor that I had to blow out quickly. FAIL! I may have just had a bad board, but I am not going to try such a board again. I'm going to plan B and ordered up a plug-in wall wart 120 volt to variable voltage DC transformer that goes down to 3 volts...similar to pictured above. I am paying a few more dollars for a quicker shipment from a US source as patience is not one my virtues! It has the mini coaxle to two screw connect wire attachment (among others). The lowest setting is 3 volts, so I will hopefully be all set with correct voltage, though I will put the voltmeter to it first to make sure. I know wall warts don't get hot, are enclosed and will be safe. I will say for the few seconds of operation on the board I had, the heat dissipation fins did get hot already, as #GUNRUNNERJOHN said they would! It the board worked and operated for like an hour of usage, the board itself may have self-combusted!!! Clearly such a board is best installed in some sort of a metal case with fan-assisted ventilation to prevent fires and board failures. I'm not even going to try the DC one, unless the wall wart's output voltage is much above 3 volts. I will post more in a week or so when the new unit comes in.

What transformer do you use? I knock down a 1033s 5v with diodes to get 3vdc.(pulsed, but works... A cap would smooth it.)

Maine Main Line posted:

I will say for the few seconds of operation on the board I had, the heat dissipation fins did get hot already, as #GUNRUNNERJOHN said they would! It the board worked and operated for like an hour of usage, the board itself may have self-combusted!!! Clearly such a board is best installed in some sort of a metal case with fan-assisted ventilation to prevent fires and board failures. I'm not even going to try the DC one, unless the wall wart's output voltage is much above 3 volts. I will post more in a week or so when the new unit comes in.

Te DC-DC board would have run cool and not gotten even noticeably warm unless you put a significant load on it.  Hard to say what happened there.

Make SURE the wall wart actually has regulated voltages or you may still have issues.  Unregulated wall warts typically only put out the rated voltage at near full current.

Nearest I can tell the Wall Wart pictured above this rated at 2000 ma max.  If the load is 20 lamps at 100 ma each that's 2000 ma.  This wall wart is gong to be running at continuous max current.  Not sure what incandescent inrush current is going to do here.

shorling posted:

Nearest I can tell the Wall Wart pictured above this rated at 2000 ma max.  If the load is 20 lamps at 100 ma each that's 2000 ma.  This wall wart is gong to be running at continuous max current.  Not sure what incandescent inrush current is going to do here.

Well, unless you unplug one or more buildings.

Yup, reducing the load is always good.  However, the thread/ photos suggest the gentlemen is running 20 lamps with a spec of 100 ma.