I have a ceiling light that is controlled by two switches, however when one of the switches is off the other switch does not work.  What is the issue and how can I fix it?
12638
I have a 3 way switch that was wired incorrectly when the switches were replaced with a different color switch.  Is there a methodical way for me to identify which wires represent which piece of the system so I can correct the bad wiring?  Currently if switch 1 is on, switch 2 can turn light on or off.  If switch 1 is off, then switch 2 does nothing.
91359
When the light is on the pad works, and vica versa. I can't see how to change this, I have tried restarting with the button pressed down while the computer is off, but that didn't work. I suspect my keyboard (a new, ultra slim one) is controlled by a micro chip, not a physical switch.
113809
I have recently seen a  and I  was wondering how it is working.  In the event of a power failure, the LED bulb will turn ON automatically. That is, when the switch is ON and mains power goes off the bulb will detect that and turn ON. If the switch is OFF bulb will not turn ON. When mains are ON and the switch is ON the bulb will start recharging again.  It is just like a normal bulb. See the   My question is, how the bulb will detect the event of mains failure? Can somebody give me a hint on this?
75213
Can somebody explain in simple words. real life example light help and limitations of these schemes etc.
92807
I would like to wire multiple motion detector light kits in parallel, so when one motion detector is tripped it will turn on all three lights.  Each light kit has 2 LED lights on it.  Schematic and text description below.
75428
What I would like to do is have an LED turn off 1 minute after the power is turned off. The LED would be on all the time when power is on. Thus:  Turn power on: LED comes on immediately. Turn power off: LED stays on for 1 minute and then turns off.  This is to signal when someones eyes have adequately adjusted to the dark in a darkroom.  Thanks in advance.
36573
I am doing some work on a ceiling light and I notice that, even though the light-switch is off, my voltage tester shows voltage present.  Answers to other questions (below) explain about phantom voltages but how exactly do I test for these and know what voltages are real and what are phantom so that I can work safely?    Phantom voltage questions
95548
I have a couple of outdoor light sockets with built in motion detectors. These seem to work as you'd expect with regular incandescent bulbs- you can set a timer for how long you want them to be on when motion is detected and they light up fine.  When replacing them with LED bulbs however they blink rapidly instead of staying on. I'm not talking about a 50hz buzz or whatever, they completely power off and on rapidly, almost like they are trying to strobe. The blinking is erratic, it will go for 10 seconds then go dark completely, then blink again for varying amounts of time. I see this same behavior with LED bulbs in both of the sockets, which are the same brand and model of motion detector outdoor light sockets.   The bulbs are Verbatim A19 6-Pack Warm White 3000K LED Bulb, Replaces 60W, Non-Dimmable 99072 if that matters.   I want to replace everything in the house with LED, but not sure how to make these two sockets work correctly. Suggestions?
31049
Random question du jour, inspired by the thoroughly depressing airport Holiday Inn I'm writing this in due to a missed flight connection:  Why don't American hotels have ceiling lights?  Every chain hotel I've ever stayed at has instead had a motley assortment of bedside, table and floor lamps.  What's more, instead of a single master light switch, there are individual switches/knobs to turn them on and off located next to the bulb, on the cable on the floor, on a switch on the side, etc, so you get to fumble around when turning them on and once more when turning them off.  And yes, I'm sure there are exceptions, but no, that doesn't make "you're wrong, I stayed at Motel Z in Bent Arm Pit, Wyoming once and they had a ceiling light!" an answer.  I'm curious about the reason why: Lower ceilings so cheaper to build?  Easier/cheaper to maintain?  Fire code?  Something else?
113825
I'm trying to build a circuit with multiple timers, each with an SPST output relay. I want to connect up my circuit so that if any of the timers reaches their set point, they turn on a beacon.  It doesn't matter how many timers reach their set point, as long as one has I want the beacon to be on. Additionally each timer will turn on its own light when it reaches the set point.  I've drawn up a circuit, but have a question, is it possible to control two lights with one SPST switch? The simplest form of the circuit I'm visualizing is shown below:  (All the Lights and Beacon and Power Supplies are 12V)    The outsides (including the switches) are the timer circuit section, while the middle part is the beacon and its power supply.  I'm particularly confused about what happens in the red path. Would that be bad for the lights? Or turn them on before the timer switches close?
18549
I read the original , I understand, but I don't do Python.  How would I "reset" my settings as shown? I've had trouble with these forever, so my Solid lighting as I work is bizarre. Even with a new startup they're kaflooey.  Added bonus: How to "put back" the settings I have now if I screw up?
59550
I've got a situation where I have a 240V 30A dryer line, and I want to power something else from the same circuit, but NEVER at the same time as the dryer. I'm looking for a switch to use, like a DPDT ON-ON break-before-make switch. There are tons of DPDT switches I've found, and most seem to be ON-OFF. Hardly any show their wiring diagrams, so if they don't give more details, I don't know if they'll work. Note: the second circuit will not use more than 15A, maybe just 12A.  I'm hoping someone can recommend specific switches that will do what I want. Manufacturer and exact part# is what I'm looking for.   Personally, I don't care if it's a knife switch, something that looks like a standard light switch, two buttons, has relays, I don't care. The breaker box is full, it's a long and difficult wire run, and I do not need a separate circuit because I'll NEVER need to run both devices at once.  I could resort to just using one plug and unplugging one then plugging the other one in, but I don't see the point of constantly exposing live wires (the plugs) where something could inadvertently fall on them or water could be sprayed, instead of keeping things all sealed in the wall with a safe, simple switch between two plugs.
113736
In my bedroom the bottom half of all receptacles are controlled by one switch. Is it possible to have just one receptacle with top and bottom hot all the time?  The top half is hot all the time the bottom half is controlled by one switch.  Keep in mind there are six other receptacles in this room that are the same way controlled by the same switch. When I took the receptacle out the right side tab had been removed.  The top right screw had a black wire, the bottom right had a red wire, the top and bottom left screws had separate white wires.  I changed the receptacle out as suggested, I capped off the red wire and I capped off the white wire that was attached to the bottom left screw. I attached the other white wire to the top left screw and attached the black wire to the top right screw. I now have none of the receptacles working at all. What did I do wrong?
12376
We have two sets: set No.1 and set No.2 as in this picture:   The observer is fixed to set No.1 . He sees set No.1 motionless and observes set No. 2 approaching with velocity 100,000 m/s.   Each set has one lamp and two, so called, touchers. Each set is designed so that if both touchers are touched simultaneously the lamp is turned on otherwise it remains off.  Set No. 2 is approaching set No. 1 so that each toucher in each set will be touched twice by the touchers of the other set.  The observer on set No. 1 observes the distance between touchers in each set 10 meters. He thinks the lamps on set No. 1 will be turned on because touchers in it will be touched simultaneously.  My question: Will the lamp on set No. 2 be turned on? How if an electrical current flowing from one toucher in a set to the other proves simultaneous touching?
61217
Recently I noticed that my led bulb turns on/off for a split second randomly over the past few days. Does this mean it is starting to die or could it be something wrong with the lamp?  I've unscrewed to see if anything was damaged but could not detect any damage.
54325
I would like to be able to control around 100 independent LEDs using an Arduino.  The problem is that the Arduino does not have nearly enough pins that can be configured for this.  What would be a way to solve this problem?  Is there a chip that can demux a more complex signal from the Arduino that could then control the LEDs?  Or is there another solution?
71563
When I connect two identical lightbulbs in series, how come they have equal brightness?  Why can't one lightbulb have a larger voltage drop than the other?  (i.e. the first lightbulb "uses up all the energy" and the second lightbulb is barely lit because "there isn't much energy left"?