Low Voltage Lighting

Need to light a display in a dark room with less-than-full brightness lights (ie, "mood" lighting). Would like to use small spots, but these are mostly
quartz-halogen bulbs. To my understanding, QH bulbs must be run at full brightness, otherwise the filiments fail to "redeposit" properly.
Also, dimming LV lighting is not straight forward (out of the box; I know anything can be done with custom controls...)
This leaves mineature incandescant spots. Wiring is a pain (mains voltage, conduit, code requirements, etc.), but if all else fails, I'll do this using a dimmer.
Suggestions?
Thanks,
--
DaveC
snipped-for-privacy@privacy.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I am running LV "Malibu" lights off of an old electric train transformer. They dim just fine. I don't think Lionel has any space age terchnology. It should be available in some other form.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

lights
using
No problems running LV halogens at levels down to 20% or so as long as you occaisionally run them at 100% to 'clean up' the deposited tungsten from the capsule wall. I use inductive rated dimmers with wirewound transformers throught out my house with LV with no lamplife issues at all. In fact I think that lamplife has actually been improved. You can bounce queries like this on sci.engr.lighting NG. regards, JB
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
--Snip--

the
lamplife
So what is the difference between a regular incandescent dimmer and a magnetic (or electronic) LV dimmer? At one time I had heard that the inc. dimmers put out a small DC offset which would than be fed to the transformer in the light fixture. Is that really the case, and is it really that bad? (bad, but how bad?)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

A simple a regular incandescent dimmer when connected to highly inductive loads can have two side-effects: 1. The dimmer might not be too accurate on the accuracy of the dimming agle both half half cycles of mains power. This can cause some DC component to be generated ot the output power. This DC component will heat up tranformer and can even cause it to saturate (saturation leads to lots of heating and can cause transformer failure). 2. The dimmer might not triger the controlling triacs always reliably with highly inductive load. This can cause that on soem dimmer settings the light could be unusable, can flicker etc.
--
Tomi Engdahl (http://www.iki.fi/then /)
Take a look at my electronics web links and documents at
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I wonder if this would help at all. Just a thought; I've never used them.
http://tinyurl.com/xj46
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If you looking for mood lighting consider switching the lights at full bright in several stages. A dimmer accepts the full load and only passes on the level you set. Using a 100 watt base and you set it for 50 % or 50 watts then your burning off 50 watts in heat. Not exactly efficient. I know it means more wiring but if you think about it you might decide that it is a better way to go. Just a wild thought from the cheap seats
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

<snip>
Nope. Modern semiconductor based dimmers (99% of those sold now) are around 95% or so efficient. They basically are on-off switches that switches on at varying points in each cycle.
I would be really, really surprised if you can even buy resistive dimmers (which even then are not quite that bad) nowadays as it's cheaper to make the semiconductor based ones rather than a high power resistor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 3 Dec 2003 7:34:39 -0800, SQLit wrote

I don't understand what you said. What are you using to switch lights at full bright in stages? Do you mean use several lights and turn on combinations of them? Or switches with resistors in stead of a dimmer?
Please clarify.
Thanks,
--
DaveC
snipped-for-privacy@privacy.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
SQLit wrote: || || If you looking for mood lighting consider switching the lights at || full bright in several stages. A dimmer accepts the full load and || only passes on the level you set. Using a 100 watt base and you set || it for 50 % or 50 watts then your burning off 50 watts in heat. Not || exactly efficient. I know it means more wiring but if you think || about it you might decide that it is a better way to go. || Just a wild thought from the cheap seats
You're wrong, to have half power you will need V_half_power=0.707V_full, the resistor would only need to dissipate 0.293Vfull at 0.707*Ifull .7W if the lamp had 100W. This assumption is for pure resistive and linear loads. In reality an incandescent bulb will reduce the heat and its resistance, so you need a little less voltage and more current for this, but the resistor will not need to dissipate more than 25W when the bulb puts out 50W. Got it?
--
ciao Ban
Bordighera, Italy
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"DaveC" wrote ...

lights
using
Some people put in multiple switched circuits so you can control the number of lights that are burning (and thus, the "mood") without any tricky equipment. Sort of a room-level equivalent of those "3-way" bulbs.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

lights
not a big problem: turn them up full every once in a while.

also not a problem: use a dimmer rated for LV. Lutron and others sell them. They cost more partly because they are only available on the high price trim lines. People who buy those trim lines are paying extra anyway. When I opened a LV dimmer up (a few years ago) the only differnce I saw compared to the standard dimmer was a snubber (RC network). You could modify it yourself but I wouldn't. Pay the extra ten bucks and let Lutron oir whoever bear any liability. BTW: if you use an electronic "transformer" (not magnetic, more like a buck SMPS) then be sure the dimmer is rated to work with *that*.

using
Either way you have code requirements: you'll be runing line voltage to the dimmer.
You haven't described your room in any detail but if you're trying to minimize the amount of line voltage wiring try looking at cable lighting systems: 2 bare wires are suspended across a space and driven by a remote tranformer. The bare wires carry only 12 volts. The fixtures hang across the bare wires. Another possibility: use a LV landscaping lighting system. Or, adapt a LV landscaping system into a cable system. All of these systems can be dimmed (see above).
Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 3 Dec 2003 12:44:38 -0800, Bob wrote

So, to summarize: 1) Full mains V, wired to standard dimmer (rated for electronic xfmr), wired to electronic xfmr, wired to LV lamps.
2) Full mains V, wired to LV dimmer, wired to LV lamps.
Do I have these options right?
Other suggestions?
Thanks,
--
DaveC
snipped-for-privacy@privacy.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

the
remote
the
LV
dimmed
wired
yup.
nope.
I don't know of any LV dimmer. That is, there is no such beast (besides designing your own) that is a dimmer and a transformer in one. (even if you design your own, I think you would have a code issue trying to run mains and LV wires in the same J box) So, 2 is not an option. Maybe you misunderstood what I meant by a LV landscaping system: they have a tranformer (often in an outdoor rated enclosure), some LV fixtures, and some wire suitable for running LV outside (buried or on the surface).
Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 4 Dec 2003 9:04:26 -0800, Bob wrote

Are electronic transformers supplied only by electronics houses? This isn't something I can find at the local electrician's supply house, is it?
Thanks,
--
DaveC
snipped-for-privacy@privacy.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bob wrote: || || I don't know of any LV dimmer. That is, there is no such beast || (besides designing your own) that is a dimmer and a transformer in || one. (even if you design your own, I think you would have a code || issue trying to run mains and LV wires in the same J box) So, 2 is || not an option. Maybe you misunderstood what I meant by a LV || landscaping system: they have a tranformer (often in an outdoor || rated enclosure), some LV fixtures, and some wire suitable for || running LV outside (buried or on the surface). || || Bob
This transformer w built in dimmer I found at this (popular) German Electronic Parts vendor. http://www1.int.conrad.com/scripts/wgate/zcop_in/~flN0YXRlPTE1NTczNjEwOTA=?%7Eevent=display&%7Etemplate=PCAT_AREA_S_BROWSE&p_page_to_display=aufriss&SPEC_AREA_GUID 8CB23C95B0380EE10000000A010251&xF&y=4
--
ciao Ban
Bordighera, Italy
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 3 Dec 2003 18:27:31 -0800, Robert Monsen wrote

Bob, Look at the bulb (when it's off!). I just replaced one in a similar lamp that was always run at low settings. The glass gets blackened from the deposits that don't get back to the filiment.
Dave
--
DaveC
snipped-for-privacy@privacy.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.