Trying to read voltage and amps on VA meter for Menards Power Adaptors

You use the scale that has a number that is the same as the number on the switch setting...disregarding the decimal point.

You only measure amps by selecting the proper mamp scale which is greater than what you expect from your circuit. You insert the meter leads between the source (transformer) and the load (resistor, bulb, what have you). The other lead of the transformer goes directly to the other side of the load. Then you will read the current (mamps) that the load draws (not the limit of the transformer which is what you refer to...2000mamp). Keep in mind that if your load is a short or draws more current than the meter is capable of measuring, you will usually blow a fuse inside the meter. I am guessing (since your picture has too much glare to read the dials) that your meter has a limit of 250 mamp.

Chuck, I don't follow you when you said use the same scale as the number on the dial setting? They don't match up at all.

5 - .5, 5, 50

10 - 1, 10, 100

25 - 2.5, 25, 250

For the matter at hand, set the meter dial to DC Volts, 0-10V.  Then use the scale as shown below.  You might first try measuring a 1.5V AA battery, 9V battery.  This is not contradicting anything the guys are telling you above.

Dale, I don't follow you. The settings on the meter for DCV are 2.5, 10, 50, and 250. Does this correspond to upper voltage readings for that setting?

Stan, I set the dial to 10 and measured the adaptor output - on the scale you circled the needle stopped about 8.5 volts. If that's the right line to read the voltage and its accurate, then the adaptors from Menards are indeed putting out more voltage then they specify - which may be the reason peoples buildings are frying (buildings need only 4.5 volts). Note, reading the scale beneath the one you circled reads 4.5 volts with dial at 10. When I set the dial to 50 and read the scale above the one you circled I get just under 5 volts.

Why is the meter ambiguous on which line of numbers to read as compared to dial setting?

Thanks everyone, still would like to know what I am doing.

Paul Kallus posted:

...

Note, reading the scale beneath the one you circled reads 4.5 volts with dial at 10. When I set the dial to 50 and read the scale above the one you circled I get just under 5 volts.

Why is the meter ambiguous on which line of numbers to read as compared to dial setting?

Thanks everyone, still would like to know what I am doing.

With the dial at 10, use the scale I circled...ignore the others.

With dial at 50, use the scale BELOW the one I circled (NOT the one above).  Since the one above indicates just under "5", the scale BELOW is indicating just under "1". With the dial set to 50, you interpret the scale BELOW as 0,10,20,30,40,50...rather than 0,1,2,3,4,5 as printed on the face.   Very confusing but that's the way it is!

Not that anyone needs more clutter around the train room, but at your convenience why not get one of those "free" with coupon Harbor Freight digital meters?  I stalked your profile and it appears there are HF stores in PA.  

Paul,

You are using an analog multimeter, do a general web search on using an analog multimeter, I did a quick search for a video showing the use of this meter and range selection or text information on using this multimeter.

Paul Kallus posted:

Dale, I don't follow you. The settings on the meter for DCV are 2.5, 10, 50, and 250. Does this correspond to upper voltage readings for that setting?

Stan, I set the dial to 10 and measured the adaptor output - on the scale you circled the needle stopped about 8.5 volts. If that's the right line to read the voltage and its accurate, then the adaptors from Menards are indeed putting out more voltage then they specify - which may be the reason peoples buildings are frying (buildings need only 4.5 volts). Note, reading the scale beneath the one you circled reads 4.5 volts with dial at 10. When I set the dial to 50 and read the scale above the one you circled I get just under 5 volts.

Why is the meter ambiguous on which line of numbers to read as compared to dial setting?

Thanks everyone, still would like to know what I am doing.

You might put your meter on 10 vdc setting and read 3 AA cells in series. Just to check the accuracy of the meter. It should read 4.5 to 5 on the 10 scale.

Paul Kallus posted:

... I set the dial to 10 and measured the adaptor output - on the scale you circled the needle stopped about 8.5 volts. If that's the right line to read the voltage and its accurate, then the adaptors from Menards are indeed putting out more voltage then they specify...

If you are reading the output with an open circuit - no load - then that is about right what you are reading. For an accurate measure, the load has to be close to the rated output(2 amps is the specification you give above in your OP). Any (expected) load will get it closer to 4.5 volts quite quickly.

Stan, with the dial set to 50 the meter reads just 1 volt (from the bottom row of the scale you cited).

Rob - I don't think I can measure with load since the meter probes have to go in the plug and on the outside to make a circuit. Are you thinking 8.5 volts would be normal in the unloaded state? Trying to figure out why some people's Menards buildings are frying.

Thanks, everyone, I'll see if I can find a digital meter.

Paul Kallus posted:

Stan, with the dial set to 50 the meter reads just 1 volt (from the bottom row of the scale you cited).

Rob - I don't think I can measure with load since the meter probes have to go in the plug and on the outside to make a circuit. Are you thinking 8.5 volts would be normal in the unloaded state? Trying to figure out why some people's Menards buildings are frying.

Thanks, everyone, I'll see if I can find a digital meter.

Right.  You should be reading just under 1 on the bottom scale.  That means just under 10 Volts which is what you got using the 0-10V dial setting and middle scale.  Again, it's confusing for sure, but you need to mentally multiply the indicated reading on the bottom scale by 10 when using the 50V DC dial setting.

As I understand it you have the 3-outlet Menards adapter.  I think what Rob is asking is to measure the voltage in one of the unused plugs.  So go ahead and plug in one building.  Now measure the voltage at one of the two unused plugs.

Okay, Stan, I was able to test the load - I plugged in 2 buildings and tested the unused plug: With dial set to 10 I measured around 7 volts; with dial set to 50 I measured just under 1 volt. If I understand you right, I need to multiply by 10 when using the "50 dial setting" ~ so that would put it around 7-9 volts. And, the 10 scale is one for one, so if right then that means the adaptor is indeed putting out more voltage then the 4.5 volts the buildings require. Could this be the reason why the guy on the main forum (he goes by Panther) buildings are frying?

fwiw, I noticed when plugging the adaptors back into the buildings the building lights go on for a second, then off, this with the household plug not plugged in. Does this mean anything, a capacitor in the adaptor maybe?

I have an old HO DC transformer - that I could potentially use for these buildings - it goes up 18 volts DC with lever, I believe. I also have to contact Menards as I have 4 of their adaptors.

I think you now have your arms around the "multiply the lower scale by 10" thing for the 50 V dial setting!

To summarize your measurements, the no-load adapter voltage is 8.5V DC.  Loaded by 2 buildings it drops to about 7V DC.  That seems a bit high to me for a 4.5V DC adapter where "full" load is 3 buildings.  As to whether or not these voltages damage Menards buildings is something I can't answer.  From what I've read, Menards does not specify operating voltage and current for various buildings...essentially saying to just use their 4.5V DC adapter.

Yes, that brief flash when you plug a disconnected (but recently powered) adapter back into a building is a capacitor inside the adapter discharging its stored energy.

Thanks for the info., Stan.

BTW: do you know what factor is for the 2.5 dial setting - and there's a 250 dial setting too.

I wrote all these notes down so that I could figure it out should I need to measure DCVolts again. I will look for a digital meter, though.

For 2.5 dial setting, use upper scale (marked 0,5,10,15,20,25) and divide the reading by 10. 

For 250 dial setting, use upper scale and multiply the reading by 10. 

The idea is that the adjustment factor makes the full-scale (needle all the way over) reading the same value as the dial setting.

As for a digital meter. Presumably you've built your layout etc. and have been running trains fine without one so obviously it's not a must-have.

In fact, if you just want to mess around with one, I will send you a new Harbor Freight digital meter (the kind you cab get Free with coupon).  Battery included!   I'll even test it first and the postage is on me!  I have a bunch of them. 

I don't see your email in your profile so email me a shipping address to this temporary email address which I'll disable after I hear from you one way or the other:

...

That's real nice of you, Stan...my friend's brother said he has one extra from Harbor Freight and will give it to me, so no need to spend postage, thanks for your offer.

Its funny, I found the instructions for the Sperry analog meter I have, and there's nothing useful in it.

I am wondering if I splice the main adaptor power cable and add 10-15 feet of wire - would that reduce the voltage? Probably a formula? I estimate the adaptor has 20 gauge wire, I could use a long run of that or even 18 gauge. I have about 8 Menards buildings that I am just now getting on my layout - just the past year I finished the track work.

Got your email.  I'll answer your question here about the dial setting of the HF meter since we may need to refer to it again.

So here's the HF meter measuring the DC output of an eBay voltage regulator module that has been set to 4.5V.  In other threads, I suggest these modules as an inexpensive way to generate regulated DC voltage for Menards and Lemax buildings, Miller signs, etc.  In this case the module even has its own digital meter showing it has been set to 4.5V DC.

Anyway, with the dial setting at 20V (left) the HF meter reads 4.51.  This would indeed be the setting to use for the Menards adapter issue at hand.  If you go to the 200V (middle) setting, note how the decimal point automatically moves for you...no need to mentally adjust the factor.  But note how you lose resolution in the measurement.  This is why you want to use the lowest dial setting that still covers the range of voltages you expect to measure.  This loss of resolution is like your analog meter's needle barely moving if the setting is too large; you can see the needle move but difficult to resolve the value. 

If you go to the 2V (right) setting, the 4.5V overwhelms the meter.  In this case the meter display just shows a "1".  Other meters might display "OF" (OverFlow), or flash, or whatever.  On an analog meter this is where the needle is pinned over to the right side.

More expensive meters have so-called "auto-ranging" capability which automatically chooses the dial setting to maximize the resolution.

As to the wire issue, yes, it's all about formulas.  Look it up in any wire-table and 20 gauge wire has a resistance of about 1 Ohm for 100 feet.  If you are running a 15 ft cable pair or 30 ft of wire that is a resistance of 0.3 Ohms.  Then you use the Ohm's Law which tells you how much Voltage you lose.  Voltage = Current x Resistance.  You need to know the Current (Amps) which, as I've previously lamented, Menards does not seem to publish.  But a reasonable guess is to note that their 1-building adapter is rated at 500mA (or 0.5 Amps) and their 3-building adapter is rated at 2000mA (or 2 Amps).  So let's just go with 0.5 Amps per building.  That means your 15 ft cable will drop/lower the voltage by 0.5 Amps x 0.3 Ohms = 0.15 Volts.  So if the voltage "started" at 4.5V DC, introducing the extra 15 ft of 20 gauge wire means the building only get 4.35 Volts.  My opinion is you shouldn't see a material difference in brightness or behavior for that small a change. 

Note that if you do make such an extension cable you will only see that voltage drop when the current is flowing into the building.  If you measure the voltage at the extended plug (not plugged into the building) you will measure the original voltage.  In other words the current is 0 Amps so the voltage drop from the 0.3 Ohm extension cable is 0 Amps x 0.3 Ohms = 0 Volts.

Finally, the HF meter also has the ability to measure DC current.   I believe we concluded that your existing analog meter only goes up to 250mA (0.25 Amps) which presumably is not enough to measure the building current.  When you get the meter, we can get into the specifics of how to measure building current with the HF meter if you are so inclined.

I'm using switch mode power supplies mentioned here on a panel with a Volt/Amp DC meter off ebay. Makes a nice easy to check source for the signs, etc.

Chuck, nice setup! 

Do you have an eBay (low-cost) source for the black jumper strip shown in your photo - I assume it's 9.5mm / 3/8" centers and it was cut-to-6 positions?

Why the electrolytic capacitor on the right edge of photo which is presumably between the + and - bus on the terminal strip?

And the $64,000 question...why is it set to 4.67V DC? 

stan2004 posted:

Chuck, nice setup! 

Do you have an eBay (low-cost) source for the black jumper strip shown in your photo - I assume it's 9.5mm / 3/8" centers and it was cut-to-6 positions?

Why the electrolytic capacitor on the right edge of photo which is presumably between the + and - bus on the terminal strip?

And the $64,000 question...why is it set to 4.67V DC? 

I got them from Mouser and cut them with side cutters...one pair that is kind of ruined for soft copper now.

http://www.mouser.com/ds/2/16/Euro7-21095.pdf

I'm using a 12 position with 6 red and 6 black using jumpers.

I found that the Miller signs power supply needed some output capacitance and just left it there when I changed to the ebay ones. 

Ah yes...I was between turns on the trim pot so I left it there. Sometimes I usually tap on the pot to get it to settle in a place that it finds comfortable and stable.

Here's my latest adventure: I picked up the HF meter at lunch break today...it was still new in package, looks to be the same one as yours, Stan. I tried it out first thing when I got home using the "20" setting on DCV and hooked probes to adaptor plug...it read nothing (0.00); I then hooked up a building to one of the plugs and tried again on an unused plug, still nothing.

Then, reverting back to the unloaded state, I started turning the dial and finally when it was on "20m" under DCA I got a reading, about 2.07, then I hooked up one building, and measured, this time the building lights went on and off and the meter readings were jumping all over the place. Not sure what's going on, but something is haywire with the meter. 

I then tried a new C battery - as simple as it gets, or so I thought - it read 0.00 under "20" DCV, but then started moving the dial around the meter until I got to 10A) and it read 1.45. This sounds right, right, cause its a 1.5 volt battery?  Or, is this meter a bust? I know my analog Sperry meter is good, at least the AC part of it, because its AC readings pretty closely matched my Z-4000 transformer digital outputs during track wiring phase of construction.

I like that you guys have voltage regulators, are these off the shelf products, or how hard are they to hook up?

Would an old HO DC transformer with variable control work too? I know I have one laying around somewhere. In theory, I could cut the wires from the Menards adaptors (leaving the plug part in the buildings) and then run all the wire pairs to the little DC transformer, and slowly crank the lever until the lights come on.

Sounds like you have the leads plugged in the wrong ports. If it's like my HF meter the red should go in the middle port and black on the bottom for voltage measurements. The upper port is for amperage. Or it could also be a bad meter?

Paul Kallus posted:

Here's my latest adventure: I picked up the HF meter at lunch break today...it was still new in package, looks to be the same one as yours, Stan. I tried it out first thing when I got home using the "20" setting on DCV and hooked probes to adaptor plug...it read nothing (0.00); I then hooked up a building to one of the plugs and tried again on an unused plug, still nothing.

Then, reverting back to the unloaded state, I started turning the dial and finally when it was on "20m" under DCA I got a reading, about 2.07, then I hooked up one building, and measured, this time the building lights went on and off and the meter readings were jumping all over the place. Not sure what's going on, but something is haywire with the meter. 

I then tried a new C battery - as simple as it gets, or so I thought - it read 0.00 under "20" DCV, but then started moving the dial around the meter until I got to 10A) and it read 1.45. This sounds right, right, cause its a 1.5 volt battery?  Or, is this meter a bust? I know my analog Sperry meter is good, at least the AC part of it, because its AC readings pretty closely matched my Z-4000 transformer digital outputs during track wiring phase of construction.

I like that you guys have voltage regulators, are these off the shelf products, or how hard are they to hook up?

Would an old HO DC transformer with variable control work too? I know I have one laying around somewhere. In theory, I could cut the wires from the Menards adaptors (leaving the plug part in the buildings) and then run all the wire pairs to the little DC transformer, and slowly crank the lever until the lights come on.

Hopefully you haven't blown the fuse inside the meter.

Anyway, plug the red lead into V^ma and plug the black lead into COM.

Turn the switch to ON.

Then set the range to 20 DCV and read the voltage.

The only setting you should use for the matter at hand is 20V DCV.   Good idea to first check a 1.5V C battery.  Do as the guys above suggest...or if a picture is a thousand words:

Not to digress, Isn't it amazing how cheap these meters have gotten? Now giveaways. 

Just like the ubiquitous 4 banger calculators you get for pennies. Back in the day I paid dearly for an HP 35 (still have) engineering calculator.  Now I see Texas Instruments that graph, polar/rectangular etc etc., and still does 4 banger math!

Ditto meters, I have a lab quality Fluke that reads to four places pass the decimal.  I paralleled a HF and Fluke and surprised how close the HF read past the decimal point.  Granted not lab precision quality, but HF would be shirt pocket good e'nuff for layout work.

Yes, I had the red plug in the top port, darn it, and read that in the instructions, but when plugged into middle port I am getting consistent results as the analog meter showed, 8.6 volts with no load, and 6.5 volts with one building plugged in. Will try with two buildings plugged in.

One thing I noticed with all 3 plugs plugged into 3 buildings, the lights are super bright, which may get back to the original guy's problem with electronics burning out.

Thanks all! I'll mess around some more.

Out of curiosity, does adding the 2nd building change the brightness of the 1st building?  And does adding the 3rd building change the brightness of 1 and 2?

Are the power connectors on the buildings accessible in a way that you could measure the voltage with all 3 buildings plugged in?

Paul Kallus posted:

Yes, I had the red plug in the top port, darn it, and read that in the instructions, but when plugged into middle port I am getting consistent results as the analog meter showed, 8.6 volts with no load, and 6.5 volts with one building plugged in. Will try with two buildings plugged in.

One thing I noticed with all 3 plugs plugged into 3 buildings, the lights are super bright, which may get back to the original guy's problem with electronics burning out.

Thanks all! I'll mess around some more.

Generally what happens when you put the leads across a source using the amps plug is that you will blow a fuse inside the meter if there is one. And if there is one, it will usually only render the amps use unusable until you replace the fuse. And who knows, the source might be a high enough impedance or the amps circuit in the meter robust, that the meter is not hurt at all.

Anyway your readings sound reasonable, 4.5 vdc regulated would be better, but it is what it is.

I am starting to lose even more confidence in the Menards Power adaptors...they appear to have been made for something cold the "Menards Gold Line" and Menards adopted them for the O-gauge buildings, not sure what the Gold line is.

Stan, I didn't notice any lessening of brightness from having 1 vs. 2 vs. 3 buildings plugged in, they're all super bright regardless. I can't see how I can measure the load with all 3 plugged in, not easily anyway.

In trying to resolve this conundrum, and short of going the voltage regulator route, and considering Menards has not responded to my question and concern, tell me what you guys think of this idea: I dug up my old Lionel transformer from an 1980s set, wow was that a cheap set, plastic wheels on rolling stock - all plastic cars, made in Mexico as I recall. Anyway, the little transformer has a variable DC output - 0-18 VDC and a constant 19 VAC terminal (that I wouldn't use), and says maximum output is 5.5 VA which I recall is the same as 5.5 watts. I think the Menards buildings draw very little amps, as the adaptors are either 1000 mamps or 2000 mamps, so even at 10 buildings and assuming 2000 mamps per building that's only 0.02 mamps x say 5 VDC ~ 0.1 VA or 0.1 watt, does that sound right? If so, then that little transformer could be used to power all my buildings at a safe load and at a comfortable light level for the visual effect. If affirmative, I could then use the female end plugs in the buildings and cut the wires and send them all to a terminal strip, and then connect the little transformer VDC output to that, and then slowly crank up the little lever until desired brightness was achieved, and never have to worry about frying the buildings electronics? I would have to run one heck of a lot of wire as the buildings are spread around my basement, but using 20 gauge wire wouldn't be so costly. What do you think? Or, is voltage regulators the way to go (I guess a new thread would be in order for that question)?

Paul Kallus posted:

Anyway, the little transformer has a variable DC output - 0-18 VDC and a constant 19 VAC terminal (that I wouldn't use), and says maximum output is 5.5 VA which I recall is the same as 5.5 watts. I think the Menards buildings draw very little amps, as the adaptors are either 1000 mamps or 2000 mamps, so even at 10 buildings and assuming 2000 mamps per building that's only 0.02 mamps x say 5 VDC ~ 0.1 VA or 0.1 watt, does that sound right? If so, then that little transformer could be used to power all my buildings at a safe load and at a comfortable light level for the visual effect.

I believe your thinking derailed Paul.

If we used your example of each building drawing 2000mamps (which really same as 2 amps) each, then you would have needed a 20 amp supply!

If we use the transformer  5.5VA  rating (which it isn't equivalent to watts, but will assume value for argument sake) and adapters rated 4.5V, then you could safely draw about 1.2 Amps or 1200 mA from transformer without harm.  So 10 buildings could draw 120 mA each, or any current combinations until reaching 1200 mA maximum.  You would need to measure each building current especially if it uses a Miller Engineering style electrolumenescent sign (their inverter power supply draws significant current I found).

Hope this helps.

RRMAN, I see your point, seems hard to fathom that each building would draw 2 amps, though, given they're LEDs, but that's what the power adaptors specify. On the little transformer at 5.5 VA - I thought volts x amps = watts? Good point on the buildings that have the Miller engineering signs, am not sure which buildings they are, though.

As I was laying in bed last night I realized something I overlooked - the Menards buildings all have different #'s of LEDs, some only have 1 or 2, while the Power plant must have close to 20. The 3 buildings I've been measuring with meter only have 1 or 2 each (and the 3 buildings that the original guy who said his burned out were all minimal lights as well). Wouldn't this then be the reason why the voltage load is still high in my measurements? Assuming I am correct, could I cut the main feed from the power adaptor (see photo) and send it to a small terminal strip (hot and common). Then, cut the 3 feeder plugs (and remove the plastic junction) and re-connect the 3 feed plugs + additional feed plugs (that I'd have to cannibalize from other adaptors) to the terminal strip and to as many buildings as it takes until the load comes closer to 4.5 volts? These are wired in parallel in original state, right? Or, would this mess up the amperage output of the adaptor? Does this make sense? I'd be cutting the wires at the location the pens in the photo show - and removing the junction - it'd be replaced with a terminal strip that could output additional plugs to 4, 5, or x # of buildings needed to bring voltage to 4.5 VDC.

I love the little Harbor Freight meters, but they do have a chronic manufacturing flaw.  The metal rings into which the test probes plug are mounted on a narrow finger branching off the main circuit board.  This little finger is supposed to be supported by a small plastic latch that provides mechanical support to hold the finger in place when you insert the test leads.  Unfortunately, many of those finger boards have either too much solder or the end of the 10 amp wire shunt is too long, and that keeps the latch from engaging the finger.  When you try to insert the test leads, the finger board bends away inside and you get no connection.

I remove the meter from the blister pack and insert the leads before I leave the store, using the ohms scale to check for continuity.  You can also look into the test lead hole after you try to insert the leads to see if the metal rings are still up toward the top of the holes and not pushed way down.   

I have had maybe 4 or 5 meters with this problem, including one just 2 weeks ago.  No problems with exchanging bad units.  This problem has been around for a couple of years.

I have the 3 outlet Menards power supply.  I plugged it into my new Menards light and power, it light up.  Tested the voltage at a second outlet from the supply and got 7.05 volts.  Won't this burn out the LEDs prematurely?

Bill

ogaugenut posted:

I have the 3 outlet Menards power supply.  I plugged it into my new Menards light and power, it light up.  Tested the voltage at a second outlet from the supply and got 7.05 volts.  Won't this burn out the LEDs prematurely?

Bill

It depends if the electronics in the building has a current regulated supply for the LEDs. If not, I would think that you might want to use a 4.5 vdc regulated supply. One question, do they get brighter if the voltage goes up and dimmer if the voltage goes down. You can check this by plugging in additional buildings to your power supply which will reduce the voltage because of loading.

Chuck and others, would it be ok to hook up say 4, 5, even 6 Menards buildings to a terminal strip that was powered by one of the Menards 4.5 VDC adaptors? The # of buildings would be determined by measuring the voltage load as I added buildings to the terminal strip, that is until the voltage was around 4.5 VDC. I guess I'd also have to measure the amp load, right, as it shouldn't exceed the adaptors output?

I'd follow your advice on using a regulated VDC supply but have no clue as to what to buy let alone install it.

I just read on the main forum another poster who reported failures in his Menards building lights.

Paul Kallus posted:

I am starting to lose even more confidence in the Menards Power adaptors...they appear to have been made for something cold the "Menards Gold Line" and Menards adopted them for the O-gauge buildings, not sure what the Gold line is.

Not sure this is relevant, do these power adapters run their Ceramic Christmas Village buildings?

Paul Kallus posted:

Chuck and others, would it be ok to hook up say 4, 5, even 6 Menards buildings to a terminal strip that was powered by one of the Menards 4.5 VDC adaptors? The # of buildings would be determined by measuring the voltage load as I added buildings to the terminal strip, that is until the voltage was around 4.5 VDC. I guess I'd also have to measure the amp load, right, as it shouldn't exceed the adaptors output?

I'd follow your advice on using a regulated VDC supply but have no clue as to what to buy let alone install it.

I just read on the main forum another poster who reported failures in his Menards building lights.

 

I'm guessing here but I would expect the voltage to go down to about 4.5 vdc, the rated voltage on the wall wart, when you draw nearer to the 2 amps. So no need to measure the current. And the wart will get warm, but not hot.

cjack posted:

ogaugenut posted:

I have the 3 outlet Menards power supply.  I plugged it into my new Menards light and power, it light up.  Tested the voltage at a second outlet from the supply and got 7.05 volts.  Won't this burn out the LEDs prematurely?

Bill

It depends if the electronics in the building has a current regulated supply for the LEDs. If not, I would think that you might want to use a 4.5 vdc regulated supply. One question, do they get brighter if the voltage goes up and dimmer if the voltage goes down. You can check this by plugging in additional buildings to your power supply which will reduce the voltage because of loading.

Now to get all technically:

Rule of thumb for Leds is whites are about 3.3V voltage drop and draw about 20mA nominal. Others have different  voltage drops dependent on color and diode materials.

That said a resistor is used to current limit Led voltage, because LEDs for the most part tend to keep a constant diode voltage drop, thus the resistor has to "take up the slack".  The Menards buildings use very small surface mount resistors that don't have alot of surface area thus low milliwatt power dissipation.

So lets say we have 4.5V  voltage and one 3.3V @ 20mA LED.  The resistor is (4.5V-3.3V)/0.020A = 60 ohms. 

Power dissipated is (0.020A * 0.020A) * 60 ohm = 0.024W well within the resistor dissipation

Retaining the resistor value lets up supply to 7,05V

(7.05V - 3.3V)/60 ohm = 0.0625 A.

Resistor power is now ( 0.0625* 0.0625) * 60 ohm  = 0.23W !! Almost a 10 fold power dissipation and after short while the resistor will burn open unless designers properly sized resistor wattage worst case.

This would explain, all things being equal, why some Menards building LEDs fail.

Any buildings of mine are powered from a regulated 4.5V supply, because you can't repair the all glued together darn things!

The Menards supplies are the cheapy transformer, diode and maybe capacitor combo.  The more transformer iron the better voltage regulation and closer the voltages stay the same with varying current load.  The 4.5V is achieved when fully loaded, lighter the load higher the voltage from the Menards adapters.  If you use an HO supply you can adjust the voltage to be 4.5V as long as all the loads remain connected. Adding or removing loads will require adjustment.  And of course items with lamps and motors that go on and off will yo-yo the supply voltage.

Clear as mud, right??  

rrman posted:

cjack posted:

ogaugenut posted:

I have the 3 outlet Menards power supply.  I plugged it into my new Menards light and power, it light up.  Tested the voltage at a second outlet from the supply and got 7.05 volts.  Won't this burn out the LEDs prematurely?

Bill

It depends if the electronics in the building has a current regulated supply for the LEDs. If not, I would think that you might want to use a 4.5 vdc regulated supply. One question, do they get brighter if the voltage goes up and dimmer if the voltage goes down. You can check this by plugging in additional buildings to your power supply which will reduce the voltage because of loading.

Now to get all technically:

Rule of thumb for Leds is whites are about 3.3V voltage drop and draw about 20mA nominal. Others have different  voltage drops dependent on color and diode materials.

That said a resistor is used to current limit Led voltage, because LEDs for the most part tend to keep a constant diode voltage drop, thus the resistor has to "take up the slack".  The Menards buildings use very small surface mount resistors that don't have alot of surface area thus low milliwatt power dissipation.

So lets say we have 4.5V  voltage and one 3.3V @ 20mA LED.  The resistor is (4.5V-3.3V)/0.020A = 60 ohms. 

Power dissipated is (0.020A * 0.020A) * 60 ohm = 0.024W well within the resistor dissipation

Retaining the resistor value lets up supply to 7,05V

(7.05V - 3.3V)/60 ohm = 0.0625 A.

Resistor power is now ( 0.0625* 0.0625) * 60 ohm  = 0.23W !! Almost a 10 fold power dissipation and after short while the resistor will burn open unless designers properly sized resistor wattage worst case.

This would explain, all things being equal, why some Menards building LEDs fail.

Any buildings of mine are powered from a regulated 4.5V supply, because you can't repair the all glued together darn things!

The Menards supplies are the cheapy transformer, diode and maybe capacitor combo.  The more transformer iron the better voltage regulation and closer the voltages stay the same with varying current load.  The 4.5V is achieved when fully loaded, lighter the load higher the voltage from the Menards adapters.  If you use an HO supply you can adjust the voltage to be 4.5V as long as all the loads remain connected. Adding or removing loads will require adjustment.  And of course items with lamps and motors that go on and off will yo-yo the supply voltage.

Clear as mud, right??  

Clear. That's a good explanation of the issues involved here. We need a good rather inexpensive source of regulated, say 3 amp switching, supplies. That just need AC in and DC out. I like the one I made, but I'm  not in the manufacturing business. It has voltage and current readout, and that is important so you know what you're doing with these somewhat expensive Miller and Menards signs.