Dimming accessory lighting

A dedicated variable transformer. 

I use two Z-1000 transformers to control the intensity of the majority of my lights and accessories that require it.

Hoping the electronic sages will provide some info.  If incandescent lighting, then voltage reduction is my method.  If it is led DC powered lighting, then for 1-3 leds a simple resistor inserted inline and valued to the desired brightness would suffice.  A diode or string of diodes will reduce voltage also in increments.  For larger numbers of DC powered leds, a buck converter may be used.

 (Provided from another thread by Stan2004)

Thanks for your help!

i am using a KW transformer and was thinking of hooking up dimmer switches between the KW and the various groups of lights. 

admittedly I am not electronic savvy and want to keep this as simple as possible.  

so can I use something as simple as a dimmer used for household lighting between the constant output of the KW and select lights on the layout?

I use ZW's,  (allow overall AC output),  through variable buck converters (convert to DC and allow separate dimming).  For example- my Todd Architectural Models Stauffer Baking, and  Menard's York Hotel are SO bright at the recommended 4.5v  DC that I use buck converters to reduce voltage to the level where they juuuust light up (about 3.5 v).  Other buildings are just fine at a higher  DC level, one to three of them operating off one converter at about 5v DC.

I end up running the ZW to about 12 v AC, and "the city" (multiple buildings and about 15 incandescent streetlights) on my layout uses a measured 12 v AC, 3.3  amps/ 40 watts.   The bump and go trolley I run off the same ZW uses about 10v AC = .7 amps or another 7 watts.  Still another approx 220 watts available assuming the transformer performs at 270 watt rated output.

Ok...now don’t all pounce on me (!)...but are the constant outputs of the kw ac or dc...yea I am that ignorant 

The KW is all AC.

@EJC-1956 posted:

..

so can I use something as simple as a dimmer used for household lighting between the constant output of the KW and select lights on the layout?

Traditional rotary/slide dimmers for household lighting assume household line-voltage coming in (i.e. 120V AC).  So if you only start from the 14V AC or 16V AC fixed outputs of a train transformer, an off-the-shelf household dimmer will not work.  If you scour the web there are no-doubt some DIY projects which modifies the components of a household dimmer to work at lower incoming AC voltages. 

Thanks to all!

@EJC-1956 posted:

What various ways are available to dim lighting accessories (street lights,etc) on my O gauge layout?  I want to have the flexibility of changing their intensity.

Is this intensity adjustment something you'd do once a day, once a week, once a year, etc.? 

Approximately how many circuits and/or potentially independent voltages are involved? 

It will just to satisfy a personal preference....if i want street lights brighter I will make them brighter...just looking for additional flexibility

i would imagine that there will be at least 5 circuits requiring independent control

ultimately i would just like some dial i could turn to control the brightness

@Train Nut posted:

A dedicated variable transformer. 

@EJC-1956 posted:

It will just to satisfy a personal preference....if i want street lights brighter I will make them brighter...just looking for additional flexibility

i would imagine that there will be at least 5 circuits requiring independent control

 

ultimately i would just like some dial i could turn to control the brightness

I think the first response was your answer.  Depending on the load for each, a collection of very small (probably available inexpensively) transformers for each one, or if your power needs warrant it, a Z(or V)  or ZW (or VW)  (slightly more expensive, but also more capability in a smaller footprint than 4 separate units) with 4 adjustments per unit.

I'd recommend Z/V since you don't need whistle or direction controllers for your application.

-Dave

So as suggested by others 5 variable output transformers would do the trick.  That is clearly the most straightforward Keep-It-Simple alternative.

Others have suggested driving your lighting with DC voltage (instead of train transformer AC voltage).  I can't think of any train lighting accessories that don't work with DC voltage.  The point being there are inexpensive adjustable DC-output voltage modules to fine-tune the voltage to the 5 circuits.  Inexpensive means just a few dollars a piece for the voltage modules.  But this does requires some attention to detail - using a voltmeter - possibly requiring some soldering - and so on.  There were some pictures posted but the economical DC-output adjustable modules typically use tiny screwdriver controls.  If doing this once a year or whatever then it's no big deal.  But if something you might be doing every day (or whatever) to suit your fancy at the time, it can be tedious...in my opinion of course.

Since you asked for alternatives, a previous post introduced the idea of using a string or ladder of diodes to provide multiple voltages from which you can pick and choose.  This method does not provide continuously-variable fine tuning.  However I think you'll find it difficult to distinguish any material difference between a bulb at 11V vs. 12V.  Your-mileage-may-vary.

The point being there have been many threads about fine-tuning AC voltages for accessories. 

Above photo is from this OGR thread.  Note the title/topic of the thread is exactly what you're asking about.  For just a few $ you can wire up some bridge rectifiers to creates a string/ladder of voltages from which you can pick an choose for each of your 5 circuits.  For select-ability you could use a common and inexpensive 3-position fan speed rotary switch (high-med-low) to choose from 3 voltages representing high-med-low brightness.  Again, this alternative does not give you continuously-variable brightness but I'm suggesting 3 brightness settings per circuit might be good enough!

I found these on eBay .  The knob is off, 50% or 100%.  They work just fine and suit my needs!

Right.  If 100% (on), 50% (dim), and 0% (off) are all you need for "adjustability" then all you need to do for incandescent lighting is to insert a diode to effect the dim mode.  A diode cuts the AC power in half (50%) since it only applies power to the bulbs on 1/2 of the AC cycle.

When O-gauge went to command-mode with its ~18V AC track voltage, a common "complaint" was the bulbs in passenger cars were suddenly too bright.  The bulbs were typically operated around, say, 12V in conventional control.  So before LED lighting was practical, the simplest solution was to insert a 10-cent diode which cuts bulb power in half.  When you do-the-math, cutting 18V AC bulb power in half using a diode drops the effective voltage to around ~12V....imagine that!