Maintaining Constant Building DC Voltage ... Regulated DC Accessory Power

The WS is not regulated.  It is variable with the 4 knobs.  There have been several earlier threads about the guts of the light hub such as:

https://ogrforum.com/...54#70974704698291754

If you need a handful of adjustable DC outputs, consider performing the AC-to-DC conversion ONCE using an inexpensive bridge-rectifier and capacitor combo.  Now you have unregulated DC for less than $2.  Then use multiple DC-to-DC converter LM2596 adjustable modules that are less than $1 (free shipping from Asia).  Or, for $2 shipped, you can get LM2596 adjustable DC-to-DC modules with integrated LED voltmeters which can be handy to monitor the different modules set to different voltages. 

In other words, for the same cost as a handful of AC-to-DC modules, you get the same functionality plus cool-looking LED digital voltmeters to monitor each output!  The effect would be something like this photo hijacked from this thread.

Stan,

Appreciate the feedback, included links of previous related forum discussions,  and confirming that the WS Light Hub is not regulated DC.

I went ahead today and ordered some of the LM2596 DC-DC Buck Converters with LED Voltmeter that you mentioned in your post ... thanks for that good idea.

Regards,

Tom

One nice thing about that DC-to-DC with voltmeter is the screw-terminals on input and output.

Actually, this being a discussion forum, I was on eBay today and couldn't believe it - an LM2596 DC-to-DC (no voltmeter) for a whopping 38 cents (free shipping from Asia)!

So if you don't mind a bit of soldering, you could pair this with a 99 cent 2-wire DC LED voltmeter to shave a few more nickels!    Or, at 38 cents for the regulated converter, you could use 2 modules with 2 different voltages and have a switch to select from 2 voltages to provide high/low brightness with the separate voltmeter monitoring just the voltage to the buildings.  Just saying!

But allow me to again get on the soapbox and lament my frustration in finding a practical/economical solution to the microscopic screwdriver adjustment of the blue trimmer potentiometers of these LM2596 modules.  Maybe it's just that I long ago lost my teenager visual acuity or my dexterity with a micro screwdriver...

There are so-called "long knob" trimmers that you can finger-adjust (no screwdriver required).  But there are minimum order quantities in the 100's or 1000's and different modules use different values (e.g., 10K, 20K, 50K Ohms).  Agreed; most guys set-it-and-forget-it...but wouldn't it be nice if the modules came with long-knob trimmers!  

Nice solution, Stan!

Stan, your problem is you don't have a couple of these for those trimmers.

One end is a recessed driver blade, you just pop it over the trimmer screw and it can't fall off as you adjust it.

S-Runner posted:

Posting here for a sanity check.   I am just beginning to plan my wiring for Menards and Woodland Scenics building lighting.  I bought one LM2596 AC/DC to DC Buck Converter and one Woodland Scenics Light Hub to experiment on how each DC power regulator controls DC power under varying building light loads.

My initial checks with digital voltmeter using transformer 15v AC accessory power, show that the LM2596 maintains near-constant DC voltage as I increase DC power load when adding additional building lights after initially setting the DC voltage output ... DC output holds very steady under varying lighting loads.  Whereas, using the Woodland Scenics Light Hub with one of the four outputs, the DC voltage output decreases as I increase DC power load by adding additional building lights after initially setting the DC voltage output ... DC output varies under varying lighting loads. 

So, it appears that the Woodland Scenics Light Hub is not a regulated power converter.  It also appears that the LM2596 is a good regulated power converter.  So, if I want to maintain a constant, say 4.5v DC, to a specific light bus in my layout where I add or remove loads occasionally, I should use an LM2596 which will maintain a constant DC output voltage as I add or remove building lighting on that bus.   Whereas, if I were to use a Woodland Scenics Light Hub to power a specific lighting bus for a group of buildings and initially set the output DC voltage to say 4.5v DC, then when I might add or remove lighting in that group of buildings, then the WS Light Hub DC output voltage would increase if I removed a light load and would decrease if I added a light load. 

Same scenario if I want to maintain say, 8v DC for a different group of buildings with other LED lighting specs.  The LM2596 would maintain a near-constant DC output voltage once initially set while the WS Light Hub output DC voltage would vary with changing lighting loads in that group of buildings. 

So, appears that I should go with more LM2596s vice more WS Light Hubs for my layout building lighting groups if I want to maintain constant DC voltage regardless of add/removing building lighting.    I also understand that many LEDs generally tolerate some variance in voltage even when spec'd at a specific voltage so some variance in DC output is likely ok.   One type of lighting that apparently doesn't tolerate DC voltage variations appears to be Menards flashing window signs and also Miller Engineering billboards and window signs that are spec'd at 4.5v DC so including them in a bus served by a LM2596 is what I'll do.  I may use the WS Light Hub that I already have for a cluster of only WS buildings.  But, if/when I expand my lighting needs, I'll opt for more LM2596s for regulating DC voltage to the added lighting buses since I can 1) vary the output voltage with its included output voltage adjusting screw and 2) maintain that voltage in a lighting bus even after add/deleting building lighting loads ... win-win.

Comments/suggestions?

 

Tom

You will definitely be pleased with your results.  I was off Menards buildings until I did the work to accomplish dimming of the lighting.  I am back to Menards as acceptable. The buildings they produce have a nice nostalgia look to them similar to Woodland Scenics.

gunrunnerjohn posted:

Stan, your problem is you don't have a couple of these for those trimmers.  

Au contraire mon ami.  Pardon my French.

I see you suggest the Spectrol version which runs $3.93 at DigiKey.  You can get the Bourns version for $1.61.   With the $2.32 I just saved you, you can buy half a dozen more of those 38 cent DC-to-DC regulators!  That's my good deed for the day and it's still morning!  Plus, the Bourns version is in blue which matches the color of the trimmers.  Color coordination is very important for the circuit to work properly.     Caterpillar yellow, John Deere green, Bourns blue...

Seriously though, in some cases these regulator modules might be upside down under the layout/table/bench and it can be a pain to fuss with an adjustment tool.  Much easier to use a long knob trimmer and your built-in tool (a.k.a. your finger) to adjust.  

Well, I did find it highly unlikely that you didn't have one, but others might not be so lucky.  As for the one I pointed to, it was the first one that came up in the search, and I'm lazy.

Stan (and all),

Here are some trimmers with knobs for 24 or 25 cents each, quantity of 1. This is from LCSC, the JLCPCB website's linked parts supply house.

https://lcsc.com/products/Prec...eter_520.html?q=3296

For unknown reasons...I can't get you a direct link to only the ones selected. You will have to select the items shown in the screen shot and then 'Apply Filters'.

Select these:  Through Hole; Chengdu Guosheng Tech; and check In Stock, then Apply Filters 

That should bring up a selection of 26 in various combinations. 

There may be more of these lurking here with other searches? Got some strange results with some of the searches I tried here. After a few attempts, I ended up searching on '3296' and found these.

Since I already have some of the Bourns trimmers with no knobs, I ordered the 'Bourns Blue' version of the special adjustment tool from Digikey.  I have been looking on ebay for one with little success... probably incorrect search terms again. 

rtr12 posted:

...Here are some trimmers with knobs for 24 or 25 cents each, quantity of 1. 

I tried 10 pieces of the 10K version at 18 cents each or $1.83.  It says $3 handling charge (for orders under $15).  It said $2.82 shipping to United States.   So about 75 cents each.  And you can pay by Paypal which makes me a bit more comfortable (though this could be a false sense of security on my part).  I'll need to poke around my regulator stash but I'm pretty sure some use 10K, some 20K, some 50K, and so on.  So after I work up what I need maybe I can get it down to 50 cents each (shipped) which seems fair enough...  

Thanks for the find! 

I used LCSC for some components for some of the traffic light PCBs. I thought LCSC offered a discount ($4 I think) for first time buyers? Maybe the offers have expired or there are minimums? Possibly more poking around on their site is needed?

Anyway, I placed two orders with them and had no problems with either. They arrived in a fairly timely manner (maybe 3 weeks or so) considering where they originated. Components seemed to be of good quality.  I too like to use Paypal for the extra safety. I very seldom place an order anymore using only a CC. 

Glad I finally found something you could use! 

Found the $4 off for first order, it's here: https://lcsc.com/activity.html#/specialdeals 

From main LCSC.com page it's under 'Special Deals' from the top menu of selections, just above main screen.

Got it!

Hmm.  Looks like I have till the end of the year!  That site has a lot of interesting stuff...kid in a candy store comes to mind.  I'll have to hunt around for more goodies so I can waive the $3 handling charge for orders under $15!  

Follow up.  The 25 cent long-knob trimpots work fine! 

By way of example, one inexpensive AC-to-DC module had the annoying characteristics that clock-wise screw adjustment decreased voltage.  Swapping in the long-knob 3-terminal trimpot backwards corrected that.  As stated previously, I've found eBay voltage regulator modules that use 10K, 20K, and 50K trimpots ... marked 103, 203, and 503.  There are undoubtedly modules that use other values too.

I figure most guys make the voltage adjustment once and done, so this modification is not worth the effort.  In my case I use these modules for prototyping ideas on the bench.  Hence the easier adjustment is a benefit worth the 25 cents part cost and a couple minutes to swap parts (soldering is required).