Snow Village AC/DC conversion

There are numerous ac to dc adjustable power supply pc boards on the bay. Do a search for "LM317 ac/dc adjustable". They are adjustable from about 1.5 vdc.

See this recent thread where I posted the following photo about generating 4.5V DC for lighting Miller signs. 

https://ogrforum.com/topic/miller-signs-1

The same method applies to recent OGR threads to light Lemax buildings using 4.5V DC, and Menards vehicles also at 4.5V DC.  It would also apply to your Snow Village if you set the output of the module to 3V - so it does require a voltmeter.

Search eBay for "AC DC LM2596 module".  Amazon also sells it (fulfilled by Amazon so U.S. shipping) but runs about $10.

The "LM2596" is an IC chip that performs the voltage regulator in a materially different way than the "LM317" IC chip that cjack suggests.  In basic terms the LM2596 would be about 4 times more efficient than the LM317 in your application of converting from, say, 14V AC down to 3V DC.  That is, the LM317 module would get very very hot dissipating 10+ Watts driving your 1.2 Amp load.

If you don't want to mess with soldering and/or you think you might want to use additional voltage converter modules for powering other DC layout accessories at different voltages, the dialog can be continued.

I see Stan beat me to it.  If you're drawing any significant current, a linear regulator is not the best choice, the switching regulators will dissipate a fraction of the power, they're much more efficient.

stan2004 posted:

See this recent thread where I posted the following photo about generating 4.5V DC for lighting Miller signs. 

https://ogrforum.com/topic/miller-signs-1

The same method applies to recent OGR threads to light Lemax buildings using 4.5V DC, and Menards vehicles also at 4.5V DC.  It would also apply to your Snow Village if you set the output of the module to 3V - so it does require a voltmeter.

Search eBay for "AC DC LM2596 module".  Amazon also sells it (fulfilled by Amazon so U.S. shipping) but runs about $10.

The "LM2596" is an IC chip that performs the voltage regulator in a materially different way than the "LM317" IC chip that cjack suggests.  In basic terms the LM2596 would be about 4 times more efficient than the LM317 in your application of converting from, say, 14V AC down to 3V DC.  That is, the LM317 module would get very very hot dissipating 10+ Watts driving your 1.2 Amp load.

If you don't want to mess with soldering and/or you think you might want to use additional voltage converter modules for powering other DC layout accessories at different voltages, the dialog can be continued.

 

Stan, thanks for the info.  I did an eBay search and brought up a bunch of those regulators.  Interestingly, all of them originate in China even though I refined the search to North America.  Somethings fooling the search engine.  Anyway, I plan to order from Amazon this time.  One more question re the power cord: one of the two wires has black dashes running its' length.  Would that be the negative or common wire?  I wouldn't want to fry any electronics because I reversed the positive and negative wires.

If you're going with a regulator module, then you'll need a multi-meter to set the output to 3.0V DC or whatever.  Use the DC voltage mode to confirm polarity (positive/negative) of your wall-wart wiring.  Yes, there are conventions on wire markings and colors for polarity indication (ribbed, smooth, solid lines, dashed lines, white, black, etc.) but I've stopped counting the exceptions to the rule that I've encountered.  It only takes a couple seconds to determine polarity of your wall-wart wiring.  Allow me to be blunt - you'd be a fool not to do so!

If this is the first time you're using the regulator modules, the potentiometer (usually blue) screw adjustment can be tricky.  Again, you'd think turning CW would increase the output and it probably does.  The adjustment range is something like 20 to 30 turns.  These devices have a clever slip mechanism so it doesn't run into a hard stop on either rotational end - it just makes a faint click and stays at the end of the range if you turn too much in either direction.  Also, the full range of output voltage adjustment is mapped to those turns.  So, in round numbers, the voltage should change about 1 Volt per turn.  If the module was set to, say, 15V output when shipped you could run into a situation where you turn the adjustment screw both CW and CCW and nothing happens.  This is because the module can only generate/regulate output voltages less than the input voltage.  So if the input is, say, 12V and the screw is set for 15V you need to turn it until the output is set to 10V, 9V, 8V or whatever before the voltmeter starts showing movement.  Nothing you wouldn't figure out yourself but may save some head-scratching!

stan2004 posted:

If you're going with a regulator module, then you'll need a multi-meter to set the output to 3.0V DC or whatever.  Use the DC voltage mode to confirm polarity (positive/negative) of your wall-wart wiring.  Yes, there are conventions on wire markings and colors for polarity indication (ribbed, smooth, solid lines, dashed lines, white, black, etc.) but I've stopped counting the exceptions to the rule that I've encountered.  It only takes a couple seconds to determine polarity of your wall-wart wiring.  Allow me to be blunt - you'd be a fool not to do so!

If this is the first time you're using the regulator modules, the potentiometer (usually blue) screw adjustment can be tricky.  Again, you'd think turning CW would increase the output and it probably does.  The adjustment range is something like 20 to 30 turns.  These devices have a clever slip mechanism so it doesn't run into a hard stop on either rotational end - it just makes a faint click and stays at the end of the range if you turn too much in either direction.  Also, the full range of output voltage adjustment is mapped to those turns.  So, in round numbers, the voltage should change about 1 Volt per turn.  If the module was set to, say, 15V output when shipped you could run into a situation where you turn the adjustment screw both CW and CCW and nothing happens.  This is because the module can only generate/regulate output voltages less than the input voltage.  So if the input is, say, 12V and the screw is set for 15V you need to turn it until the output is set to 10V, 9V, 8V or whatever before the voltmeter starts showing movement.  Nothing you wouldn't figure out yourself but may save some head-scratching!

Stan, some versions of the LM2596 have an led voltage meter, a bit more expensive, but appears to be useful.  What's confusing to me is no model # difference.

BILL HUDSON posted:

Stan, some versions of the LM2596 have an led voltage meter, a bit more expensive, but appears to be useful.  What's confusing to me is no model # difference.

If by no model # difference you mean they all say LM2596?  That's because the IC chip that does the voltage regulation is the LM2596 even in those modules that include the digital LED voltmeter.  As you've probably seen you can get the integrated voltmeter version for less than $3 on eBay (free shipping from Asia).   There are usually U.S. sellers for all these things that mark up prices.  If these guys actually did some value-added like verify functionality, or write-up an instruction sheet in English, then I'd be happier.  I guess it's a question of how fast you think you need the item.  I seem to get eBay electronic widgets in about 2-3 weeks on average though I'm on the West Coast and they do seem to transit thru San Francisco based on the tracking numbers some provide.

As for the integrated voltmeter, it is kind of neat though in your case you'd use it once to set to 3.0V and then never need it again!  Yes, these are kind of cool since you can switch mode to have it measure the input voltage and/or the output voltage, or to even shutdown the display to save power.  BUT to be clear, it cannot measure polarity.  So it cannot be used to measure the DC polarity of your wall-wart.   Upon reflection, given the cost of a basic hobby-grade digital multimeter, I'd think anyone messing with trains should have one.

Yes, they all say LM2596.   There is also an LM2596T which is more expensive and I'm sure has more functions.  You are correct that once I get the regulator set up, it will be a permanent one.  I do have a Greenlee multimeter.

Thanks

Well, to peel a layer of the onion, the LM2596 IC chip comes in 2 package type indicated by the suffix letter or LM2596T vs. LM2596S.  The lowest cost modules use the LM2596S version so I suppose to be precise they should say LM2596S in their title but why bother.  The "T" version allows a heatsink (note screw mounting hole in package) to be used which increases the allowed power dissipation in the module.  Given your application you shouldn't need this extra power capability.  I see on eBay the "T" version modules sometime use the term "plate" in the title.  I'm guessing that the word "plate" refers to the heatsink.  If I was  more curious I'd go into a Chinese-to-English dictionary to see how the Chinese word for "heatsink" or "heat sink" translates...probably thinks heat and sink has to do with kitchen utensils and hence plate comes out?

Anyway, initially you said you were going to power this from a ZW.  Recently you're asking about polarized "DC" inputs and regulator modules with integrated voltmeter.  Most I've seen (with LED voltmeter) are DC-to-DC rather than AC/DC-to-DC.  Are you now planning to power from a DC-output wall-wart or something other than a ZW?   Just want to be sure the original assumptions apply since there are technical considerations that may be in play - left out of the discussion to keep from descending into techno-babble.

stan2004 posted:

Well, to peel a layer of the onion, the LM2596 IC chip comes in 2 package type indicated by the suffix letter or LM2596T vs. LM2596S.  The lowest cost modules use the LM2596S version so I suppose to be precise they should say LM2596S in their title but why bother.  The "T" version allows a heatsink (note screw mounting hole in package) to be used which increases the allowed power dissipation in the module.  Given your application you shouldn't need this extra power capability.  I see on eBay the "T" version modules sometime use the term "plate" in the title.  I'm guessing that the word "plate" refers to the heatsink.  If I was  more curious I'd go into a Chinese-to-English dictionary to see how the Chinese word for "heatsink" or "heat sink" translates...probably thinks heat and sink has to do with kitchen utensils and hence plate comes out?

Anyway, initially you said you were going to power this from a ZW.  Recently you're asking about polarized "DC" inputs and regulator modules with integrated voltmeter.  Most I've seen (with LED voltmeter) are DC-to-DC rather than AC/DC-to-DC.  Are you now planning to power from a DC-output wall-wart or something other than a ZW?   Just want to be sure the original assumptions apply since there are technical considerations that may be in play - left out of the discussion to keep from descending into techno-babble.

The product title on the eBay says ac/dc to dc.  I think it's also stated in the product description.  I have noticed that some of these with same product # are DC to DC, so I knew not to get that.

Follow up:  ordered product on eBay 21 Jan.  It is coming from China as all those listed are.  It arrived in NYC 6 days ago via "epacket" at "ISC".  Our Gov security at work here?

What is epacket ?

It's a subsidy using your tax dollars to help China sell stuff cheaply in the US.

"It's possible for an individual to send a pound of stuff from Hong Kong to D.C. for less than it would cost to send the same package from, say, Seattle."

Ship anything from China to U.S, is much cheaper than ship from U.S to China

Below is the description from the USPS website.

I'm on west coast so my eBay epackets from Asia transit thru the San Francisco ISC (there are 5 USPS International Service Centers).  On average, it has taken about 1 week after tracking shows it at the ISC to then reach my mailbox.

Well, the Gov gods finally released the converter;  it came in the mail a few minutes ago.  The item has two connection points - one is in the middle of the board adjacent to the voltage adjustment screw and the connector points are marked "+" & "-".  The other one is on one end and has no polarity markings.  Which one of the terminals is the input?  With no pos/neg markings does it matter?

What is/was your eBay item #?

I'm sure there are variants but all the ones I've seen have 4 connection points, 2 inputs on one side, 2 outputs on the other side...clearly labeled IN and OUT.  + and - also labeled for outputs.  No polarity for inputs.  Sometimes printing is on back of board.

A picture would help.

I have now tested with an output wire.  Picture of converter and multimeter reading attached.  Instead of an adjustment screw, they added a knob.  Still, the adjustment, as you said, is very sensitive.  I was not able to get it to remain on 3.0v, so did test at 3.1.  Perhaps 2.9v will read about 3.0 on the multimeter.  Will a tenth or two higher voltage damage the accessory?  Now the accessory spec also indicates output amps @ 1.2.  I don't have a test device to get an amp reading, plus, my multimeter has a max 200ma capacity.  Any suggestions?  I would think that over amperage will damage the accessory.  The power source I'm using is a very small transformer from an old low end kit.  Use it a lot to test bulbs, etc.

A tenth of a volt is not significant, just get it close.  Don't worry about the amp rating, it only draws the current it needs.

Thanks.  That is good news.  Only thing left before I do a test with the accessory is to determine which wire on the AC wall plug is negative.  Both wires are white, with one having black dashes running its' length; the other has alpha-numeric characters running its' length - can't read or make sense of that.

I have to use the original wire because the other end has a jack that plugs into the diner.  The diner has two jack inputs, one for the power supply and the other for the accessory (sign).  That configuration was done because the diner has a bright red "Diner" sign on the front of the building that is lighted by same power source.

Use your meter on the DC voltage setting, when you get a positive reading on the display, the red lead is on the positive terminal of the P/S.

Bingo.  It works.  Again, thanks so much for your help.

Bill

BILL HUDSON posted:

Picture of converter and multimeter reading attached.  Instead of an adjustment screw, they added a knob. 

...

I don't have a test device to get an amp reading, plus, my multimeter has a max 200ma capacity.  Any suggestions?

Learn something new everyday.  I wasn't aware that some sellers offer a knob variant on the LM2596 regulator modules.  I'm not sure I like the lack of adjustment resolution in the "B" version but it got the job done for you so.   And they did Send A Version...just not the "A" version. 

As for DC current measurements, according to your zip there's a Harbor Freight near you.  You can get a Free basic meter with coupon (Sunday paper) that has 10 Amp DC current capability.  Battery included too!