Dimmer

[rudywa]

Any of you Electrical experts know how to take the 19v AC output on my power pack usually used for accessories, dim the output with a variable knob so the bulbs last longer, I use the DC on spare packs to dim lights but I would like to be able to do that with my 19v AC leads.

Thank You

Actually, I think I found a workarpund, many bulb types require different volts so I found these Cables Unlimited AUD-6000 that I can cut off the leads like Miller Engineering power packs, then I can select any one of 6 different voltages on the powerpacks to match bulb or less. -Thanks

[JoeinPA]

 The simplest way would be to place a high watt resister in series with one of the AC feeds.  The value (Ohms) of the resister would be determined by how much dimming you want.

Joe

[jkeaton]

Or, put a diode in series with the lights, if half-voltage would do the job for you. One plus - no resistor heat to deal with.  Negative - only half-voltage as an option.  (yes, actually half-wave DC, but the effective power is half of the AC supplied)

[CSX Robert]

You could use multiple pairs of standard silicon diodes, each pair wired in parallel but with opposite polarity, and the multiple pairs wired in series with each other. Each pair of diodes would drop the voltage by ~0.7 volts.

[Allegheny2-6-6-6]

 No the simplest way is to go buy a wall wart transformer for about $10.00 in a lower voltage. If you are not 100% sure of what your doing with electricity it's best off you don't mess with stuff like that. The way my luck runs I would have the FD in my dirve way the next day drowning  my layout with a 2" line.

[richhotrain]

Allegheny2-6-6-6

 No the simplest way is to go buy a wall wart transformer for about $10.00 in a lower voltage. If you are not 100% sure of what your doing with electricity it's best off you don't mess with stuff like that. The way my luck runs I would have the FD in my dirve way the next day drowning  my layout with a 2" line.

That's the way I would go too.   Why take chances if you don't know what you are doing?

[jwhitten]

JoeinPA

 The simplest way would be to place a high watt resister in series with one of the AC feeds.  The value (Ohms) of the resister would be determined by how much dimming you want.

Joe

 

 

Be careful not to burn your fingers!

(Or anything else-- that's asking for trouble if you're not certain what you're up to.)

[JoeinPA]

jwhitten

 

Be careful not to burn your fingers!

(Or anything else-- that's asking for trouble if you're not certain what you're up to.)

I guess my problem is that I continually assume that people use common sense.

Joe

[jwhitten]

JoeinPA

jwhitten

 

Be careful not to burn your fingers!

(Or anything else-- that's asking for trouble if you're not certain what you're up to.)

I guess my problem is that I continually assume that people use common sense.

Joe

 

 

I find that, despite its moniker, common sense usually ain't.

 

John

[jeffrey-wimberly]

 The way I did it years ago was to wire a lamp dimmer in line between the wall socket and the power pack I was using.

[JoeinPA]

jeffrey-wimberly

 The way I did it years ago was to wire a lamp dimmer in line between the wall socket and the power pack I was using.

 

Jeffrey:

That reminds me of an acquaintance who was using a variable transformer (Variac) set to 10 volts to power his lights.  He failed to lock down the adjustment knob and it got bumped and "migrated" to a much higher voltage with an interesting fireworks display from his pike.

Joe

[jeffrey-wimberly]

JoeinPA

jeffrey-wimberly

 The way I did it years ago was to wire a lamp dimmer in line between the wall socket and the power pack I was using.

 

Jeffrey:

That reminds me of an acquaintance who was using a variable transformer (Variac) set to 10 volts to power his lights.  He failed to lock down the adjustment knob and it got bumped and "migrated" to a much higher voltage with an interesting fireworks display from his pike.

Joe

I never had that problem. Being the careful fellow that I am I taped the dimmer knob in place so it couldn't be moved.

[Doc in CT]

 If you buy the "wall wart", double check the voltage with a meter.  I checked a 9volt the other day and it was pumping out 15volts !!

[jeffrey-wimberly]

Doc in CT

 If you buy the "wall wart", double check the voltage with a meter.  I checked a 9volt the other day and it was pumping out 15volts !!

Many of the wall warts will put out a higher voltage without a load. The voltage indicated on the label is the voltage expected under load.

[Mark R.]

jeffrey-wimberly

 The way I did it years ago was to wire a lamp dimmer in line between the wall socket and the power pack I was using.

I'm thinking you got lucky - I would NOT recommend controlling a transformer with a dimmer !!!

All phase control dimmers are non-linear loads. A non-linear load is one where current is not in proportion to voltage. The non-linear load on dimming systems is caused by the fact that current is switched on for only part of the line cycle by a phase control dimming system. This non-linear load creates harmonic distortion on the service feeder. Excess harmonic currents cause conductors and the steel cores of transformers and motors to heat. Sometimes the heating of the distribution transformer can be a problem, because transformers are rated for undistorted 50 Hz or 60 Hz load currents. When load currents are non-linear and have substantial harmonic content, they cause considerably more heating than the same undistorted current.

You could be asking for trouble should sufficient heat builds up causing the core to break down. A definite fire potential would be at stake here !

Mark.

[Alantrains]

 

yes you're right. I smoked a 12volt transformer by plugging it into a light dimmer. Lots of unpleasant smoke and a dead 2 amp transformer! Put your bulbs in series (2 at a time will halve the voltage) its much safer.

[jeffrey-wimberly]

Mark R.

I'm thinking you got lucky - I would NOT recommend controlling a transformer with a dimmer !!!

Maybe I did get lucky. It was an older Bachmann trainset power pack and an analog type dimmer that worked with a potentiometer. I used it wired inline with the power pack for over a year without the pack even getting warm. All it did was supply current to structure lights.

[rudywa]

Was the dimmer between power and transforer or the transformer and lights?

[jeffrey-wimberly]

rudywa

Was the dimmer between power and transforer or the transformer and lights?

Between power and power pack.

[rrinker]

 Probably got lucky then, they DO make dimmers for inductive loads that would work OK with a transformer, but the common kind sold for dimming incandescent lights is not going to work and will have the results mentioned above.

 I'd say use the diode method, it works well, is cheap and simple and nothing gets hot. I did that on an N scale layout I built a long time ago and it worked very well.

                                    --Randy