Contents:
Personally, I think touch lamps are one of the dumber uses of technology to appear on this planet but that is just my opinion :-). These are susceptible to damage from voltage surges or just plain old random failures. In addition, the current surge that often results at the instant an incandescent bulb burns out (the bright flash) may blow the thyristor in the electronics module. If the lamp is stuck on, the thyristor is probably shorted. The specific part can be replaced but to be sure it is bad, some testing will be needed and it is probably soldered in place. However, if you have repaired an ordinary lamp, you will be able to replace the entire module fairly easily. If the lamp is stuck off, there could be a bad connection or bad bulb, or the electronics module is defective. Again, replacement is straightforward. Erratic problems could be due to bad connections, dried up electrolytic capacitors (especially if the electronics module is near the hot bulb), or even external E/M interference (e.g., a dimmer or vacuum cleaner on the same circuit). Some problems are of the following type: "I have 2 touch lamps in the bed room and they are both plugged in to the same receptacle. Every once in a while the lamps come on by themselves for no apparent reason. Even more strange is that every so often just one lamp turns on by itself." (From: Tim Moore (tmoore@interserf.net)). These use a MOSFET type circuit to switch the lamps on and off. The circuit is attached to the metal in the lamp base. When you touch it the impedance changes ever so minutely but enough to change the MOSFET from off to on and visa versa. My wife could never get our lamps to switch, she often had to blow on her hand first to get it moist so it would make better contact. Here is part of the problem. It takes a certain amount of signal from the lamp base to switch the circuit. Electronic parts all have acceptable ranges of operation and when put into identical circuits they sometimes perform differently. One circuit might need a good hard touch while the other might need only a slight touch. Power surges would often switch one of my lamps, although it didn't happen often. A strong radio signal could do it too. The bottom line is that these lamps are not rocket science and can't be counted on as 100% reliable. Sorry, that's the truth. You give up a little to get the convenience of just having to touch them. I ended up removing mine - an electrical storm wiped one out and wiped the other out a few years later.
While many people swear by touch lamps, nearly as many swear at them since in addition to frequent failures (bulb burn-outs killing the triac, for example), they can also be tempermental, cycling through their brightness settings and/or turning on or off due to static electricity, power line transients causing RFI, and stray pickup from the local ham rig. (Portions from: John Evans - N0HJ (jaevans@codenet.net)). Here is a fix my buddy, Ed, a fellow ham radio operator, has come up with to solve this problem. As usual it took 8 months and 10 minutes to fix. Two parts: 1/4 watt, 1k Ohm resistor and 2.5 mH 1/2 watt size molded coil. Connect in-line with the touch wire. I send 2 or more watts from my rig. My son works the CB. You'll find it on when you get home. So the darn thing is an oscillator which changes frequency when you touch it. The circuit does the rest. By adding the resistor/inductor pair, its sensitivity is reduced and the problem disappears. One more thing: (Most important!), you won't hear interference FROM the oscillator in the lamp anymore on your radio. And don't open up the module inside the lamp base, you are wasting your time there, and adding more work to glue the module back together. Just Choke off the sense wire with the resistor and 2.5 mH choke. You'll be fine.
A fixture is normally permanently mounted to a wall or ceiling. However, aside from not usually having a plug - being directly wired - they are similar to table lamps in what is inside. There will be one or more sockets for light bulbs - often all wired in parallel so that all the bulbs come on at the same time. For wall fixtures, there may be a switch on the fixture though most often the switch is mounted on the wall elsewhere. Unlike table lamps where most of the heat rises from the bulb away from the socket, mounting the sockets horizontally or inverted (base up) can result in substantial heating and eventual deterioration of the socket and wiring. Common problems relate to this type of problem - bad connections or brittle wire insulation. Replacement parts are generally available at home centers and electrical supply houses. Just make sure to kill power before working on any fixture wired into your house's electrical system!
Turn off power and double check! Wear safety goggles to protect against flying bits of glass. Then use a pair of needlenose pliers or any other tool that will grip what is left of the base to twist it free. A piece of a raw potato may even work!
Christmas and other decorative lights are constructed as series strings
of low voltage light bulbs as shown below:
Bulbs
Male o------O----O----O----O----O----O----O----O---+
Plug |
o---------------------------------------------+
Or the following which permits several strings to be connected end-to-end:
+---------------------------------------------+
| Bulbs |
Male o--+---O----O----O----O----O----O----O----O---+ +--o Female
Plug | Socket
o---------------------------------------------+-----o
Many variations on these are possible including multiple interleaved series
strings. One of the bulbs in each circuit may be a flasher. All newer light
sets must include a fuse as well.
In a series connected circuit, if one bulb burns out, all lights go out. The
newer types include a device in each bulb which is supposed to mechanically
short out that bulb if it burns out. However, these don't always work or you
may have a set that doesn't have this feature.
The following assumes a single series circuit - large light sets (e.g.,
perhaps 50 or more) will have multiple series strings so you will have
to identify the particular circuit that is bad. If more than one bulb
is burnt out, this may further complicate matters.
To locate a burnt out bulb in a series string, you can use the binary search
approach: pull a bulb in the middle of the string. Test the bulb and between
the power cord end and the middle for low resistance. If these are ok, you
know the bad bulb is in the other half. Then divide the 'bad' portion in half
and test one half of it and so forth. For example, using this technique, you
will need to make at most 6 sets of measurements to locate a bad bulb in a 50
light set.
Sears, K-Mart, Radio Shack, among others sell inexpensive testers (e.g.,
Lite-Tester Plus, about $4). These detect the electric field generated by
the (now floating) wire on the Hot side of the gap of the burnt out filament.
These will also locate open wires and blown fuses in the same manner.
I have also heard of bulb sets in which the individual bulbs are gas filled
in such a way that if the filament breaks, current flows across the gap
through the gas resulting in a faint glow in the burnt out bulb. I don't
know if these things still exist.
WARNING: Do not be tempted to bypass a bad bulb with a wire. This will reduce
the total resistance and increase the current to the remaining lamps shortening
their life. Do this a few times, and the entire string will pop. This is a
serious safety hazard especially on older light sets that may not have internal
fuses. Some fuses look like lamps - replace only with an identical fuse - not
with a lamp!
Original type of problem: No light but fuses are good and no obvious damage. (From: Ken Bouchard (bouchard@ime.net)). My advice, is trash them and go out and buy new ones. After all, you can get them typically around 5-10 bucks a set. Then you have the old set to raid bulbs from, for the ones that blow out. Quality control is not an issue when they build xmas lights. One slight tug of a wire, can break it, and the entire set goes dead. First I assume you wiggled all the bulbs, often just a loose bulb causes this. In the smaller type bulb sets the string is wired in sections, so one bulb goes out, and every 4th or 5th one is dead. The little bulbs were also designed, that if the filament breaks in the bulb a piece of foil inside it shorts out that bulb so that the remaining lights keep on working. This works up to a point, until more than 4-5 bulbs blow out at once, then the remaining ones get too much voltage and blow out too. Often the cheesy sockets get water in them and corrode, and/or the wires on the bulb get twisted or broken. They also use a cheap method of crimping the wiring together in these lights. Most times you can find the broken wire, by inspecting, seeing where it goes into the socket it pulls out easily. Well avoid doing this when the set is live (heh...) unless you like the idea of getting zapped.
Although the specific case of controlling a fixture or outlet from exactly
two locations is a special case of switches at more than 2 locations, each
is described separately since the former is much more common.
Should you care, these implement the multiple input XOR (exclusive OR) logic
function for controlling electrical devices.
Note: See the section: "Dimmer switches and light dimmers" if you would like
to have control of brightness of a lamp or fixture from multiple locations.
* For exactly two locations (say at the bottom and top of basement stairs), you
will need a pair of what are known as 3-way switches.
These are actually SPDT (Single Pole Double Throw) switches which look like
ordinary wall switches but have 3 screws instead of 2. Two of these screws
will be the same color (usually brass) while the third will be different
(darker copper or brown). They may be marked as well.
Note that a socket for a 3-way bulb for a lamp is not related to this - only
the name is similar.
Typical wiring for controlling a fixture or outlet from exactly two locations
is as follows:
Location 1 Location 2
3-way SW A 3-way SW +---------+
/o----------------o\ | Fixture |
Hot o-----/ \o-----------| or |--------o Neutral
o----------------o Center | Outlet | Shell
B (brass) +---------+ (silver)
/o---o o---o
A 3-way switch connects either up o---/ or down o---o\ .
o---o \o---o
As usual, the brass screw on the fixture or outlet should be connected to
the Hot side of the wiring and the silver screw to the Neutral side.
Another common variation is shown below:
Location 1 Location 2
3-way SW Rd : 3-way SW
: Bk /o------------------o\
Hot o-------------------------------/ Wh : \o---+
: o------------------o |
+---------+ : : |
| Fixture | : Wh Splice Bk : |
Neutral o-------| or |---------------X---------------------------+
| Outlet | : (Wirenut) :
+---------+ 14-2 14-3
Details may differ for your particular installation (like to which sides the
Hot and Neutral are connected and/or particular wire colors used).
* For more than two locations (say at 3 doors to your dining room), you will
need a combination of 3-way switches and 4-way switches. Two of the 3-way
type will be needed at the ends of the circuit (below) with 1 or more 4-way
type in between. Thus for 'n' switch locations, n-2 of the 4-way switches
will be needed.
4-way switches have 4 terminals arranged as two pairs. In one position pair
1 is connected to pair 2 straight through. In the other position, the
connections are interchanged.
Typical wiring for controlling a fixture or outlet from 3 or more locations
is as follows:
Location 1 Location 2 Location 3
3-way SW A 4-way SW A 3-way SW +---------+
/o------------o\ /o-----------o\ | Fixture |
Hot o---/ / \o---------| or |---o Neutral
o------------o/ \o-----------o Center | Outlet | Shell
B B (brass) +---------+ (silver)
o---o o\ /o
A 4-way switch connects either straight or exchange / .
o---o o/ \o
This can be extended to an arbitrary number of positions.
As usual, the brass screw on the fixture or outlet should be connected to
the Hot side of the wiring and the silver screw to the Neutral side.
Note that a 4-way switch can be constructed from a DPDT (Double Pole Double
Throw) type (e.g., toggle switch) as follows:
+--------------+
| |
A(in) o---------------+ |
| | |
+----o o/ o-------+------o A(out)
: | |
+----o o/ o---+----------o B(out)
| | DPDT |
B(in) o---------------+ toggle |
| switch |
+------------------+
For low voltage (non-house wiring) or panel mount applications, this may be
easier than using actual 4-way switches (which are probably not available in
small sizes).
The 3-way switches (at least the basic white, ivory, or brown toggle type)
can be found nearly anyplace that sells common electrical devices including
hardware stores and home centers. You may have to look a little harder for
4-way switches as well as styles or colors to match your decor as these are
not as widely available. However, a decent electrical supply house should
have all of these.
The wires marked A and B (sometimes called 'travelers') may be in a single
(Romex) cable and should be on the screws that are both the same color.
If you do use Romex with a black and white wire, put black tape on the
insulation at the ends of the white wire (or paint the ends black) to
indicate that this is a Hot wire and not a Neutral. This is required by
Code but allows the use of this type of wire.
These diagrams represent one wiring arrangement. Sometimes, there are other
slight variations. For example, you might find the switches in the Neutral
instead of Hot portion of the wiring - however, this is not recommended.
(Also see the section: "Controlling a fixture or outlet from multiple locations".) So you forgot to label the wires before you removed the old switch, huh? :-). You have several options: * It may be obvious from the way the box is wired as to which are the A/B pair. * Use a tester to figure out which wire is which (see below). * Interchange the different colored screw wire with one of the others. If this doesn't fix it, interchange the different colored screw wire with the other one. As long as you have only touched the wires on the old switch, you cannot damage anything by doing this. * Get an electrician. Of course, kill power before touching or changing anything! Here is one way to identify the proper wires more quickly than trial and error: 1. Identify the Hot wire. With all 3 wires in each box disconnected and their ends exposed, use a tester between each one and the a earth ground (the box if metal and properly grounded). With power on, only one of the 6 wires will be live. Now, turn off the power and confirm that it is off by retesting the hot wire you identified above. 2. Connect the lone screw (the different or darker colored one) on one switch to this Hot wire. Connect the same-color screws on the switch to the other two wires. This should take care of one box. 3. With any luck, you should be able to connect the wires in the other box exactly the same way color wise. (From: CodeElectric@Worldnet.att.net). Check both boxes. There will be a single Hot - that goes on the common of the 3-way switch. Put the other two wires on the other two screws. Now, at the other switch, you will find one hot. Put that on a screw, not the common. Switch the other switch, and you'll find another hot. That is the other traveler. You've got one wire left,,, that's the other common. In more detail: First, shut off the power to the circuit. Then remove the wires from the switches. Ignore the colors of the wires... there's too many combinations to use so the colors won't mean anything. Look closely at the switches. You will find one screw different from the other two. It may be black, while the other 2 are gold, or may have the word 'common' printed near it. This is, (duh!) the 'common' terminal. The other two are 'traveler' terminals. Having identified the commons and travelers, make sure your family knows you're working with live wires, and let them know not to touch!!!! Turn the power back on, and out of the six wires that came off of the two switches, ONE of them will have power. Once you find that one, turn the power back off, and hook that one wire to the common terminal of a switch. Hook the other two wires in that box to the traveler terminals. It doesn't matter which one goes where. Put the switch into the box, and place the cover back on. You're done with than switch. Now turn the power back on, and check the remaining three wires. One will be hot. Flip the first switch, and another will be hot. These are your traveler wires. Turn the power back off, and hook those two wires to the two traveler terminals on the second switch. Again, it makes no difference which goes where. The final wire goes to the common terminal. Button everything up, and you should be done. Turn the power back on, and you should be up and running.
In the old days, a dimmer was a large high wattage rheostat put in series with the light bulb. These were both inefficient and producers of a lot of heat. Modern dimmers use a device called a triac (a type of thyristor) which is a solid state switch to control illumination by turning the light bulb on for only a part of each AC half-cycle (100 or 120 times a second depending on where you live) as determined by the adjustment knob or slider. Once switched on, it remains on for the remainder of the half-cycle: * For low intensity, the current is switched on late in the half-cycle. * For medium intensity, the current is switched on around the middle of the half-cycle. * For high intensity, the current is switched on early in the half-cycle. * For full intensity, the triac may be bypassed entirely. There will probably be a detectable click position with the control set to full brightness if this is present. Dimmers are available to replace standard wall switches and even for use in place of the light bulb socket/switch in most table lamps. However, nearly all of these are designed only for normal incandescent light bulbs - not fluorescents, compact fluorescents, or high intensity or halogen lamps (or any other type of lamp with a transformer). (There are special dimmers for use with fluorescent lamps but these must be specifically matched to the lamp type and wattage and their dimming range is usually not very wide. See: the fluorescent lamp information at http://www.misty.com/~don/light.html for a discussion of dimming techniques and details on several relatively simple approaches that may work for your needs.) Installation is generally very straightforward as there are only two wires and polarity does not matter. They simply replace the existing switch. To assure long life, it is best to select a dimmer with a higher power rating than your maximum load. For example, if you are using four 100 W bulbs, a 600 W dimmer should be the minimum choice and one rated at 1000 W would be better. This is particularly true if halogen bulbs are used since these may be harder on dimmers than normal types. Further derating should be applied where multiple dimmers are installed in the same outlet box resulting in greater combined heating. Higher wattage dimmer switches will have better heat sinking as well which should result in the active components - the thyristors - running cooler. Dimmers are under the most stress and generate the most heat when operating at about 50% output. Dimmers may fail due to power surges, excess load, momentary fault (short) at the instant of light bulb failure, or just plain old age. A failed dimmer will generally be stuck at full brightness since the thyristor will have shorted out. The mechanical on-off switch which is part of the dimmer will probably still work. * A power surge may result in a failed dimmer just like any other solid state device. * Make sure you are nor overloading the circuit controlled by the dimmer. Most common types are rated for 600 W maximum with heavy duty types up to 1200 W or more. My advice is to not load them to more than 60-75% of their rating. * When light bulbs burn out, there can be an instantaneous spike of high current due to the failure mechanism. This may blow a fuse or trip a circuit breaker - but it may also blow out a dimmer control. * Dimmers are not always of the highest quality design or construction and parts may run hot - ever touch the wall plate of a dimmer running at 50% power? Long term reliability may not be that great. It is not generally worth worrying about repair of a dimmer as they are so inexpensive. However, before replacement confirm that there is no actual problem with the wiring (like a short circuit in the fixture) and that you are not overloading the dimmer.
These are the type of common light dimmers (e.g., replacements for standard wall switches) widely available at hardware stores and home centers. While designed for incandescent or heating loads only, these will generally work to some extent with universal motors as well as fluorescent lamps down to about 30 to 50 percent brightness. Long term reliability is unknown for these non-supported applications. CAUTION: Note that a dimmer should not be wired to control an outlet since it would be possible to plug a device into the outlet which might be incompatible with the dimmer resulting in a safety or fire hazard.
The first schematic is of a normal (2-way) inexpensive dimmer - in fact this
contains just about the minimal number of components to work at all!
S1 is part of the control assembly which includes R1.
The rheostat, R1, varies the amount of resistance in the RC trigger circuit.
The enables the firing angle of the triac to be adjusted throughout nearly
the entire length of each half cycle of the power line AC waveform. When
fired early in the cycle, the light is bright; when fired late in the cycle,
the light is dimmed. Due to some unavoidable (at least for these cheap
dimmers) interaction between the load and the line, there is some hysteresis
with respect to the dimmest setting: It will be necessary to turn up the
control a little beyond the point where it turns fully off to get the light
to come back on again.
Black o--------------------------------+--------+
| |
| | |
R1 \ | |
185 K /<-+ |
\ v CW |
| __|__ TH1
| _\/\_ Q2008LT
+---|>| / | 600 V
| |<|--' |
C1 _|_ Diac |
.1 uF --- (part of |
S1 | TH1) |
Black o------/ ---------------------+-----------+
The parts that fail most often are the triac, TH1, or the combination
switch/control (S1/R1).
There are at least two varieties of inexpensive 3-way style dimmer switches which differ mainly in the switch configuration, not the dimmer circuitry. You will probably have no reliable way of telling them apart without testing or disassembly. None of the simple 3-way dimmer controls permit totally independent dimming from multiple locations. With some, a dimmer can be installed at only one switch location. Fully electronic approaches (e.g., 'X10') using master programmers and addressable slave modules can be used to control the intensity of light fixtures or switch appliances on or off from anywhere in the house. See the section: "True (electronic) 3-way (or more) dimmers". However, for one simple, if inelegant, approach to independent dimming, see the section: "Independent dimming from two locations - kludge #3251".
The schematic below is of one that is essentially a normal 3-way switch with
the dimmer in series with the common wire. Only one of these should be
installed in a 3-way circuit. The other switch should be a normal 3-way
type. Otherwise, the setting of the dimmer at one location will always
affect the behavior of the other one (only when the remote dimmer is at its
highest setting - full on - will the local dimmer have a full range and
vice-versa).
Note that the primary difference between this 3-way dimmer schematic and
the normal dimmer schematic shown above is the addition of an SPDT switch -
which is exactly what is in a regular 3-way wall switch. However, this
dimmer also includes a choke (L1) and capacitor (C2) to suppress Radio
Frequency Interference (RFI). Operation is otherwise identical to that
of the simpler circuit.
This type of 3-way dimmer can be used at only one end of a multiple switch
circuit. All the other switches should be conventional 3-way or 4-way types.
Thus, control of brightness is possible only from one location. See the
section: "True (electronic) 3-way (or more) dimmers" for reasons for thistrue
restriction and for more flexible approaches.
Red 1 o--------o
\
S1 o----+------------+-----------+
| | |
Red 2 o--------o | R1 \ ^ CW |
| 220 K /<-+ |
| \ | |
| | | |
| +--+ |
| | |
| R2 / |
C2 _|_ 47 K \ |
.047 uF --- / __|__ TH1
| | _\/\_ SC141B
| +---|>| / | 200 V
| | |<|--' |
| C1 _|_ D1 |
| .062 uF --- Diac |
| | |
Black o-----------------+---CCCCCC---+-----------+
L1
40 T #18, 2 layers
1/4" x 1" ferrite core
The parts that fail most often are the triac, TH1, or the combination
switch/control (S1/R1).
The schematic below is of a 3-way dimmer with a slightly more complex
switching arrangement such that when the local dimmer is set to full on or
full off, it is bypassed. (If you ignore the intermediate dimming range of
the control, it behaves just like a normal 3-way switch.) With this scheme,
it is possible to have dimmers at both locations without the dimmer
circuitry ever being in series and resulting in peculiar behavior.
Whether this is really useful or not is another story. The wiring would be
as follows:
Location 1 Location 2
3-way Dimmer A 3-way Dimmer +---------+
/o----------------------o\ | Lamp |
Hot o------o/ Silver 1 Silver 2 \o------| or |-----o Neutral
Brass o----------------------o Brass | Fixture |
Silver 2 B Silver 1 +---------+
(If dimming interacts, interchange the A and B wires to the silver screws at
one dimmer).
This one uses a toggle style potentiometer where the up and down positions
operate the switches. Therefore, it has 3 states: Brass to Silver 1 (fully
up), dim between Brass and Silver 1 (intermediate positions), and Brass to
Silver 2 (fully down).
Br /o---o Br o---o Br/\/o---o
3-way dimmer is up o---o/ S1 or down o---o\ S1 or Dim o---o S1
o---o \o---o o---o
S2 S2 S2
However, it is still not possible to have totally independent control - local
behavior differs based on the setting of the remote dimmer (details left as
an exercise for the reader).
Like the previous circuit, this dimmer also includes a choke (L1) and
capacitor (C3) to suppress Radio Frequency Interference (RFI). It is just
a coincidence (or a matter of cost) that the 3-way dimmers have RFI filters
and the 2-way type shown above does not.
Silver 1 o---+----------------+--------------------+-----------+
| | | |
| | R1 \ ^ Up |
| | 150 K /<-+ |
| | \ | |
| | | | |
| | +---------+--+ |
| | | | |
| C3 _|_ | R2 / |
| --- | 22 K \ |
| | | / __|__ TH1
| | C2 _|_ | _\/\_
| | .047 uF --- +---|>| / | 200 V
Up \ | | | |<|--' |
| | | C1 _|_ D1 |
| | |.047 uF --- Diac |
| | | | |
| Dim o--------+---CCCC---+---------+-----------+
| / L1
Brass o---+---o 12T #18
1/4" x 1/2" ferrite core
Down o
|
Silver 2 o-----------+
The parts that fail most often are the triac, TH1, or the combination
switch/control (S1/S2/R1).
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