regulating accessory voltage

In general it's easier to power accessories that require precise voltage control with a dedicated small transformer (40-50 watts or less). However if I am reading your question properly it sounds like you are looking for a way to reduce the fixed voltage output on the Z1000. The easiest way to do this is with a voltage regulator, which is a solid state device that limits the voltage in a circuit. Essentially a voltage regulator works like a pressure switch - when the voltage is below a set threshold nothing happens, but if the voltage is above the threshold the excess voltage is returned to ground, whereas the circuit only receives the threshold voltage.

If you can post which voltage you want to limit your output to, I can provide you with the parts list and wiring diagram.

-John

You've just stumbled on a major disadvantage of the Z-1000 compared to the CW-80, which has an infinitely variable accessory output.

There are many ways to reduce 14VAC to 12VAC ranging from one or a few electronic components like resistors and diodes - with costs starting less than $1.  It depends on what you are trying to do.

When you use the term regulate it can be surprisingly complex and expensive to generate an adjustable regulated 12VAC voltage.  Regulated in power supply terms generally means the voltage does not change as the load changes. So it comes down to how much voltage change your application(s) can tolerate.  Usually model train requirements are not that stringent so tell us more about what you are trying to accomplish. It may also turn out that your application can run on 12VDC (instead of just 12VAC) which gives you additional options.

The amount of power (Watts) is another parameter you need to consider as components to regulate voltage are characterized by how much power they can handle.

Consider a 12 volt wall wart transformer.

Those are notoriously not regulated - typically with open-circuit outputs of 18 volts or more.

If you collect enough wall wart units, you will have some that are regulated.  I toss any from defunct items in a large box, when I need one I just dig through the box for an appropriate model.

Rob

Mine are fixed 12 volt which I understood was his need rather than variable voltage. 

They may say say 12 volts, but check them out with a meter - you will be surprised. As Lee alludes, a regulated wart is elusive... they are usually from some kind of computer equipment.  And those that are regulated are usually DC.

I've never seen or heard of a regulated AC wallwart, those would be REALLY rare!  However, the DC ones are much more common, at least I have a lot of regulated DC wallwarts in my collection.

On the meter @ top right, stays at 12 volts constantly.  I'll sign off on this now.

Neither have I. But they must exist somewhere.

Dewey, if you have one, we'd like to see it - it doesn't show in your photo, and it might help the OP accomplish what he's trying to do.

Dewey,

I just built my first gadget for the layout yesterday.

I want to see the voltage that is being applied to the tracks.

This way now I can see where I am at at all times.

Planning on building another set for scenery and lights.

Dewey,

Since we have no idea what that meter is measuring, what are we supposed to take away from this "information"?

Last year, I was looking for a way to fine tune the voltage for each operating accessory without having to resort to separate transformers for each one.

One of the guys here posted a simple method for lowering the voltage for each device by wiring a series of rectifiers into the wire going to each accessory. I put one together but never installed it.

I'm not in your guys category relative to knowing this kind of stuff, but I could swear that I have  a REGULATED wall-wart that pumps out AC.  It's a Radio Shack one where I can set the voltage to various values.  I use it to power my Miller signs and I had Chris approve it before I bought it to make sure that it was REGULATED.

I don't recall the key word that says that it's regulated, but mine has that key word in the label describing the inputs and outputs.

Radio Shack calls it a transformer.  Does that make it NOT a wall-wart?

- walt

John

Measuring the output of the 12 volt wart powering 17 Tortoise motors.

Rob 

The wart is plugged into the power strip and located almost dead center of the power center shown in the photo. Its output wire run is up to the two position barrier strip above and then on to strips that power the turnout motors.

Maybe.  If it hangs on a wall outlet when you plug it it, it's a wall-wart.

Here's a RS AC regulated wall-wart:

I just looked at the Radio Shack web site and it says it's VDC output. 

Sorry about adding confusion to the discussion.

- walt

I'd still like to hear from the OP as to what he's trying to do!  It may be that he really needs AC voltage to drive his accessories - such as those with an AC vibrator mechanism.  And he may indeed need to adjust the voltage to fine-tune the sometimes finicky behavior of these accessories.

Radio Shack calls the above an "AC Adapter" because it plugs into the AC wall socket.  But as Walt confirms, it puts out a DC voltage.  Other sellers might call it a DC Adapter or an AC-DC adapter.  That's what I call confusing.

Regulating AC voltage is a squirrely affair even if you meter the voltage.  There was a recent thread (sorry, no link) where simply measuring the AC voltage gave wildly varying results depending on the type of meter. This was because some model train controllers chop up the AC signal to regulate voltage and this confounds a typical hobby-grade meter.  Then in a separate thread (sorry, no link) it was shown that a smoke unit (which might be in an accessory) works better if the 12VAC is of the chopped AC variety.

So I can imagine a situation where someone was advised an accessory works best at 12VAC.  But this was based on using a chopped AC-controller (like the Z-1000) measured with an economy meter.  So that someone hooks up a regulated 12VAC source (non-chopped), confirms 12VAC with a meter, and faces disillusionment.

Uhh... It has a DC output, it just plugs into AC.

I think he is asking for a rheostat. I might be the only forum member that endorses their use.:-) 

I read that i don't know how many times and read it as AC.  It's in fact DC.

Well, they did say AC in the title.

I love a rheostat for its intended use, keeping in mind that it is a current limiting, not voltage limiting device. A drop in voltage can be one of the effects of using a rheostat when used in a circuit.

I agree that it is current limiting. But, since it is a resistance, it takes on the function of a voltage divider when the rheostat and the accessory are in series. BTW I am not challenging you Rob. Only mean to clarify my position.

My plan is to run a few accessories and lcd lights for about 6 buildings.  I don't know what voltage I will end up needing as don't have all the accessories, but thought the 14 volts out of the z-1000 would likely have to be brought down.

So, if i group lights and accessories into similar voltages can is split the 14 volts dc at a terminal strip and have a different voltage regulator going out to each group.

Thanks for all the info.  As with most things technical, half the battle is understanding the vocabulary and I'm not there yet.

For that, your best bet is to set up a diode array as Dale H describes here so you have several options to choose from for different needs/accessories.

Wouldn't one of these work that can be had for less than 6 dollars on ebay

Except he needs/wants/has AC.

I think the diodes Rob suggested are the best choice.

I agree with diodes if you know the target voltage. I believe that the poster is estimating his voltage need when he asks for a knob to adjust the voltage. Hence my rheostat recommendation.