How to reduce voltage...

I am attempting to power a crane that requires 12 volts of DC. The fixed DC voltage on my transformer produces 20 volts. I know I could power the crane with a small additional power pack, but I would prefer to have one transformer do all functions. Is there some electrical devise that I could put inline to reduce the voltage? Thanks, Jim

 

There are 12V voltage limiter/regulators. The trick is finding a small one. There are millions of large and not-so-efficient ones; every car ever built has one.

 

Thanks Rick. Sounds like what I need.

 

A simple voltage divider circuit would work as well if you have room for a small couple of resistors

 

I use pololu step up regulators to turn single rechargeable AAA and AA into 3.3v to run LEDs and logic for my monorails.

They also make them the other way round as step down and they are tiny!

500ma draw

https://www.pololu.com/product/2846

1 amp

https://www.pololu.com/product/2834

I hope this helps, look forward to picture or video.

 

We use the same devices which I believe are called Buckboards and get them from eBay at a cost of about £2.42 for 5 of them.

https://www.ebay.co.uk/itm/5PC-Mini...put-0-8-FSA-/253852251363?hash=item3b1ac5f4e3

Our oNeTrack modules have a continuous 24vac bus alongside the DCC bus. From this we can dial down any voltage up to 20vdc on any module, sometimes using 2 or more on any one board if the need is there. Very convenient.
Cheers, Ted

 

Hi Jim -

You've already received some good recommendations. I'll add one more.

This module, available on eBay, is really easy to use:
https://www.ebay.com/itm/LM2596-Buc...4-0-40-to-1-3-37V-LED-Voltmeter-/400802470941



It accepts an input voltage of up to 40 vDC and its output is adjustable over a wide range. Your 20 vDC power supply will work fine with the module.

I've even made a YouTube video that explains how to use it:


One reason I like the module is that it has a built-in display that shows the output voltage, making it easy to adjust without a separate voltmeter. Thanks to forum member Spookshow for bringing this module to our attention.

- Jeff

 

Jeff,

Thanks for the very informative post and I guess I missed Spookshow's posting.

If you don't mind, I have a couple of questions :

1). After calibrating in your video, if you had changed power supply to let's say a 6 volt walwart, would the left (in) side have read the 6 volts or whatever that ww put out and be fairly accurate ? I know that typically a walwart puts out approx, 1-1.5 or more, depending on quality of item, volts than it is rated for.

2). I use a lot of 3v nano LEDs on a refinery module scene and do not use resistors because I use a regulated 3v walwart. Is this unit considered regulated so that I could use one of these to power up approx. 80 LED's, without resistors, with one unit ?

Thanks,
Carl

 

Hi Carl -

1) For whatever reasons, I have not had any luck using this voltage converter module with wall warts. An LED on the module that should illuminate in the presence of input voltage remains off. Perhaps the module is not tolerant of ripple on its input. I'm don't know what the problem is. Since I'm using the modules with good quality DC power supplies, I done very little investigating with wall warts.

2) The LM2596 chip used in these modules is capable of excellent regulation of the output voltage. Here is a spec sheet for the chip from Texas Instruments:
http://www.ti.com/lit/ds/symlink/lm2596.pdf

I've experimented with using this module without resistors to power LEDs. This worked fine. However, I have not tried it with nano LEDs, and my testing involved only 8 LEDs and lasted only a few hours.

Since the modules are inexpensive -- a bit more than $2 --I suggest you purchase a few and do some testing of your own. Only you can decide if the module is suited to your needs.

Good luck!

- Jeff

 

Carl, 80 LEDs at .02 amp is 1.6 amps at 3.3v . That’s a hefty wallwart.


I’d like to offer an alternative:


Your typical 5v 2.1amp phone charger box would only need a modest resistor. Something stupidly low like 33 -66 ohms would be more than ample to reduce them to under .02 amps per. And you can always start high and add more resistors to reduce the value (3 x100 ohm in parallel is 33 ohms. 2x is 50 ohms) if you want to play with illumination levels. The benefit here, is that they are easily replaceable at Walmart, even the gas station, if one fails.

That’s how I run the 7 color changers on Epcot building, with a simple resistor, because I needed the 5v input for charging both the interior speaker and the iPod.

There are also Chinese lighting boards for 20+ LEDs that can be daisy chained to run off one 5v 2amp Phone charger, at $15 per, they aren’t the cheapest of options, but they will allow you to group LEDs and have different dimming/levels.
Street lights, home lights, factory lights, etc.
I did this on my Contemporary so I could balance the different light sources.
Also keep in mind, if you are talking about fairy lights, they have their own resistors built in and count as 1 LED only. I run three sets of 20 and treat each set as a single LED.
Just a different (easier) approach perhaps.

 

Thanks Jeff and Richard for your inputs, much appreciated. I am not a total newbie with regards to using LED's. I have put several into my N scale locos both steam and diesel and I have used many of Evans Design's "Pico .8mm" LEDs and their regulated power supply. Their walart output is 3v - 2000ma. Am quite happy with the results, so I must show off with one of my favorite images. Jeff, I told you that I had 80 LEDs and I actually have many more but I have two independent circuits with one having 60 and the other 50 LEDs.



Hope you enjoy.

yellow-cad : Pardon me for hijacking your thread but my post is concerning reduced voltage,
Carl

 

No problem. I got a couple of good responses for my use and it's always nice to see an innovative layout.