I am finding out walwart (ac to dc adapters) voltages are way off as far as the DC output voltage they claim to provide. Is this true ? Are they reaaly off that much ?
I would like to use some I saved for accessories but they outputs are wild. The stated outputs are no where near what they are listed at and if using LED's - they will blow them out instantly with higher than rated voltages.
Are any walwarts even worth using. Your thoughts are appreciated.
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None of the voltage readings are useful unless they are connected to a load. If the wall wart is unregulated, it will only deliver the rated voltage with the load for which it was designed.
@Freight Train Jim posted:I am finding out walwart (ac to dc adapters) voltages are way off as far as the DC output voltage they claim to provide. Is this true ? Are they reaaly off that much ?
I would like to use some I saved for accessories but they outputs are wild. The stated outputs are no where near what they are listed at and if using LED's - they will blow them out instantly with higher than rated voltages.
Are any walwarts even worth using. Your thoughts are appreciated.
Jim,
If they all seem to be excessively high, and it's because they're unregulated, the voltage will drop when you connect them to your load. The question is will they drop far enough to be in the correct range for the load?
You're absolutely correct. If they don't drop into range it could easily kill your load.
The only sure way to test them is to apply a test load that matches your actual load. This would normally be a resistor whose value is determined by Ohm's law, i.e. V = I x R.
Since we want R we'll use this form: R = V / I. Divide a walwart's rated output voltage by it's rated output current and you'll get a resistance value. Connect a resistor of this value across the walwart's output and then measure the voltage across it. If the walwart's good it will read within 10% of the rated output voltage. In other words it should only be a little bit high or low at this point and not a lot.
(Warning: When you do this please make sure that the resistor you choose is chubby enough to safely take the power it will be receiving from the walwart without overheating. For this we use P = V x I, in this case Rated Output Voltage times Rated Output Current, and we get a wattage rating for the resistor, and double it to be safe.)
Mike
It might also be worth mentioning that the Power formula Mike gave uses engineering/scientific abbreviations.
P = Power in Watts
V = Volts (as you probably know)
I = Current in Amps
I'm about to ditch my wallwarts for an old HO transformer and a regulated buck converter.
Agreed that the wallarts are not the best source of power but they are cheap and readily available.
10 vdc from the transformer= 4 vdc output (adjustable)
Many wallwarts are regulated, those typically are pretty close to the label voltage. You can usually tell, the regulated ones are a lot lighter, they normally use a switching power supply as that keeps the cost down for a given power output.
A salvaged computer power supply works well for me. Most are rated over 300 watts, with 12 vdc, 5 vdc, and 3.5 vdc taps.I power all my buildings with the 12 volts, using LED strips. The 5 volt tap and a diode powers Miller signs. I power my brewery and diners with smoke with buck converters to cut the amount of smoke. Crossing gates, flashing signals, 6' of under layout LED strips, and some motorized accessories also are dc. They also have lightning fast circuit protection. I'm still not up to 6 amps total with everything on.
"It might also be worth mentioning that the Power formula Mike gave uses engineering/scientific abbreviations.
P = Power in Watts
V = Volts (as you probably know)
I = Current in Amps"
--------------------------------
"E" (electromotive force) = Volts
So the equation for Watts is P = IE
Picky, picky, picky.
Thanks to @SteveH and @Arthur P. Bloom, for clarifying the terms I used.
You're right on the money here.
Mike
Sorry, my Bell System training kicked in.
It's not picky if you're communicating with others who use these terms regularly. One person's "picky" is another's "attention to detail" or "accuracy" or "precision in writing" or "Before I throw this big switch, what do you suppose this guy means, Boss?" or ...
I had a supervisor who insisted that all these terms were always to be capitalized because they were originally based upon the surnames of famous inventors. Her reasoning was "They need to be remembered. Someday people will ask 'Why do we capitalize these terms?' And hopefully they will learn about these geniuses."
Volts, (Allessandro Volta), Amps, (André-Marie Ampère), Watts (James Watt), Farads, (Michael Faraday), Henries, (Joseph Henry) etc. Even though the group she supervised was a bunch of electrical engineers and assistants, she made sure we knew these names and who they were, and their personal histories.
As John says there are regulated and non regulated wall warts. If you have some already just use a voltmeter, unloaded, to determine what type it is. Buying new search on regulated supplies. Miller Engineering sells a 4.5v regulated supply for his signs and says you can use a regulated 5v as well but an unregulated 5v wall wart will blow them up.
Pete
I have an older version of this one. Each of the settings are very close to the stated value.
https://www.parts-express.com/...y-120-536?quantity=1
John
On the Lemax power adaptors, they're advertised as "switching." I thought that meant a regulated output, but now I am not so sure.
FWIW: they've been very reliable for my Lemax buildings.
I think if you measure the output of most "switching" supplies, you'll find they actually are regulated. They may be up to around 10% off the rated voltage, but they'll be close enough for government work. 
https://ogrforum.com/...3#172471169543265783
"Sorry, my Bell System training kicked in."
With all the stuff coming from Asia that little detail could save a lot of time and effort. In my previous life I worked with a group supporting beta testing of our new products. One guy was having a heck of time getting consistent results from a security access system. I asked him to explain his results, he told me half the control board would work correctly until they applied a software fix for the other half that had a problem. Getting those guys on a conference call was a pain since both the hardware and software engineering was being done in India, that is when I smiled. I told him in that part of the world you don't turn on the water tap, you open the tap to get water, close the tap to stop it. They also don't turn on the light, they "open" the light. Once he got the project managers, software and hardware engineers, manufacturing people together they were able to come to an understand of what "Normally Open" and "Normally Closed" means in EE terms,.
Makes me wonder about all these various power supplies we have for everything,
Mike in NC,
@RSJB18 posted:I'm about to ditch my wallwarts for an old HO transformer and a regulated buck converter.
Agreed that the wallarts are not the best source of power but they are cheap and readily available.10 vdc from the transformer= 4 vdc output (adjustable)
Are we just going to ignore he has a double-ended adjustable wrench on his workbench?
On a more serious note, I like the screw terminals and standoff holes on that PCB.
@gunrunnerjohn posted:I think if you measure the output of most "switching" supplies, you'll find they actually are regulated. They may be up to around 10% off the rated voltage, but they'll be close enough for government work.
Yes, just tested my Lemax 4.5 V DC adaptors, they're right in the ballpark 
@illinoiscentral posted:Are we just going to ignore he has a double-ended adjustable wrench on his workbench?
On a more serious note, I like the screw terminals and standoff holes on that PCB.
🤣🤣🤣🤣
I found that in my Wife's grandfather's shop. He was a carpenter for the NYC Parks Dept. It's never too far away and I use it all the time. Not for fixing trains tho...😉
The boards are well made. I will take advantage of the mounting holes when I install them.
Bob
what is a good definition of a "walwart" ?
Thanks in advance,
CB&Q Bill
It's a "wart" that hangs on the wall! 
Thanks guys for all the info and comments. The power of the OGR Forum lives on.
I got back into HO slot cars over the holidays, and learned some things about substitute power supplies. A good one is a universal laptop battery charger with adjustable voltage. I found one on Amazon for around $30, goes up to 24VDC and rated for 5A with a bunch of adapters. It has a dial to vary the output and a digital display for the voltage.
@gunrunnerjohn posted:It's a "wart" that hangs on the wall!
One online explanation is that "wart" is a derogatory term because the device covers up the adjacent socket and renders it unusable. Maybe an etymologist will jump in here to elucidate.
@Bruce Brown posted:One online explanation is that "wart" is a derogatory term because the device covers up the adjacent socket and renders it unusable. Maybe an etymologist will jump in here to elucidate.
One look at the typical outlet or power strip near a model train layout, and the connection (see what I did there? 
) is obvious. Now, if someone can only come up with an effective treatment for an etymologist infestation . . . 
@CK posted:I got back into HO slot cars over the holidays, and learned some things...
I quickly found that having each slot powered by its own supply was instrumental in making racing these more enjoyable.
"Now, if someone can only come up with an effective treatment for an etymologist infestation . . . "
Your demand is our supply...or something...
These 1-foot long cords allow the oversized warts to dangle, thus freeing up the adjacent receptacle which would be covered by the over-weight warts. Lots of clever variations: multiple outlets, piggy-back outlets, splitters, etc.
@Arthur P. Bloom posted:"Now, if someone can only come up with an effective treatment for an etymologist infestation . . . "
Your demand is our supply...or something...
These 1-foot long cords allow the oversized warts to dangle, thus freeing up the adjacent receptacle which would be covered by the over-weight warts. Lots of clever variations: multiple outlets, piggy-back outlets, splitters, etc.
If you don't feel like paying Amazon's inflated prices, try MonoPrice.
Total with shipping for six is a little more than Amazon's price for one!
GRJ: Such a deal!
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