Why Do Some X10 Lights Turn On Automatically



I installed an Appliance Module on my fish tank. I can send a signal to turn it off, but a few seconds later it's on again. Do I have a ghost in my house?
Actually, this is a common question for our tech support team members. We have an answer to this strange X10 problem and a couple of solutions to use to eliminate this annoyance.
Most aquarium lights use fluorescent bulbs powered by ballast transformers. The fluorescent light should give you some idea where the problem is centered. Now don't get defensive about fluorescent lights, I like them too, and for some applications, they are a great source of lighting. The problem is the ballast transformer that drives the bulbs. This unit will convert the 120 volts of AC voltage to some higher voltage that powers the bulbs.
The primary component of an electromagnetic ballast is a core of stacked steel laminations surrounded by wound coils of insulated wire. This core & coil design functions both as a voltage transformer and a current limiter. Another component used in many electromagnetic ballast transformers is a capacitor. The capacitor allows the ballast to utilize energy from the power line more efficiently. This capacitor is the primary cause of the Appliance Module turning back on after it was commanded by X10 signals to turn off. Below is a typical diagram of a fluorescent lamp circuit.
Inside Lamp and Appliance modules is a circuit feature called 'Local Control'. The X10 engineers wanted to make owning and operating X10 modules more convenient to the users, so this feature was built into modules. If you had a table lamp plugged into a module and wanted to manually turn on the light, without local control, you would have to find a transmitter and send an X10 'ON' signal to that lamp's plug-in module. If the X10 module has local control, you can simply walk up to the table lamp and turn the lamp's power switch a couple times and the module would come on. The modules local control circuit is always monitoring the lamp's power switch to check if someone is trying to turn it on manually. When it senses this, it automatically turns itself on and begins supply electricity to the lamp. Pretty cool!
This local control circuitry can be easily fooled when connected to some loads, like fluorescent lamps. The local control circuitry will put a small amount of current (a few milliamps) into the load and it monitors that current to notice any difference. On an incandescent light bulb, it can easily recognize when someone is flipping the on-off switch. The problem with fluorescent lamps is the local control circuitry doesn't know how to interpret the readings it gets back from the lamp's ballast transformer. When the Appliance Module shuts off the power to the lamp, the light does indeed turn off for a second or two, and then the local control circuitry notices something and turns the light back on. At less than $15 each, they could not build too much intelligence into these modules, so not knowing any better, the module will always come back on. The local control feature may cause an AM/FM radio to operate at reduced volume or a coffee pot's indicator light to glow dimly when either is connected to an Appliance Module and the module is turned off.)There are two ways to defeat the local control circuitry. Depending on your level of confidence and skill with electrical components, you can either open the module and modify it or use an external device to fix the problem.Click to see larger imageSince the plug-in module is putting out a small voltage across the load and fluorescent lamp's impedance values are changing in the few moments after being turned off, the idea is to use something that will absorb the power from the module. To do this, connect a cube tap to the Appliance Module and then plug a small wattage night-light into the same module as the light. When the fluorescent lamp is off, the night-light will soak up the small amount of current the module used to monitor whatever is plugged into the module's output plug. The night-light will come on when the module is on, but this is a small price to pay to fix the problem. When the fluorescent lamp is off, the night-light will also be off.For those of you who need more of a challenge, the module's internal electronics can be modified to disable it's local control feature. Before proceeding, please understand that this information is intended as instructional; it is not intended to be a tutorial for modifying electronic circuits. Any modifications to any piece of electronics will void its warranty and UL approval. Please remember that you are dealing with a device that run on 120VAC. Always disconnect the device from AC power before attempting any modifications, as lethal voltages may be present while the device is plugged in. Smarthome.com assumes no liability for damage or harm caused directly or indirectly by modified equipment.Click to see the back side of the module's PC board!Open up the module by removing the two screws on the back of the unit and unlatching the two catches at the bottom of the module. The backside of the module should come off. Keeping the front of the module down and a surface, lift the PC board from the rest of the plastic case. At this point, you should have what resembles the photo on the left. Inside the module, soldered to the board there is one integrated circuit labeled "PICO-570", "PICO-536C", or something "570". Cut the lead that goes from pin 7 of this integrated circuit to the hot AC connection. Click on the graphic to see where to cut on the soldered side of the circuit board. Once re-assembled, the local control circuitry will be disabled and fluorescent aquarium lights will stay off when switched off by X10 signals.There is another reason why you might want to disable the local control feature. The local control feature can also be the cause of a module randomly turning itself on. If the 120-volt power dips or browns out, it could cause the module to think that someone is trying to locally control the lamp or the appliance connected to the module. This will only be a problem with modules that have local control. Many of the older, brown-colored, plug-in modules are especially prone to this problem. Replacing these types of modules with new ones usually fixes the problem. LampLinc and ApplianceLinc have Selectable Local ControlSmarthome's new ApplianceLinc and LampLinc modules offer a local control function that can be easily disabled with electrically modifying the module. The local control feature is enabled or disabled during the setting of the module's primary address. To disable the feature, put the module in to the programming mode (press and hold the Set Button for three seconds), send the X10 address and an OFF command to the module (B6-OFF). To enable it, follow the same procedure, except, you'll send an ON command (B6-ON).
Click to read more about this productIf all this modification is too much to handle, we do offer in-wall X10 Receptacles without local control. These modules are often used because they have a clean appearance and there is no module box sticking out of the wall. These units will replace the existing wall outlet with an X10 intelligent model. The specifications are a little better than a plug-in Appliance module. Best sure to choose either the 15-amp Leviton Duplex Receptacle #2245W or 2245I or the 20-amp Leviton Heavy Duty X10 Receptacles # 2243W or 2243I.
So, let there be light on when we want it and ghosts in our homes only during Halloween.updated 7/21/03

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