I discovered a cool way for remotely controlling something using an extra wireless phone. We had used a wireless phone for some years. It had two handsets, one at the base unit and another one that sat in a charger in another room.
Later, we wanted to add a third handset in yet another room. The easiest way to do it was to buy a three-handset system so we replaced the whole setup, locating the third handset and its respective charger in the new room.
I boxed up the old two-handset phone system and set it aside.
One day, we decided we wanted to have a lamp that we could control from a remote location. There was power available where the lamp was to be located but there were no easy ways to provide a control signal. I considered an X-10 control system which delivers control signals through the power wiring but I am cheap and so I look for ways to do things without spending money.
I pondered the idea of how difficult it would be to use the spare wireless phone system to do the job and it turned out to be surprisingly easy. Basically, I just needed to add an AC adapter to provide a source of DC power, a solid state relay, a modular phone plug to fit the phone base, and the wiring for the lamp.
The schematic shows how I connected everything.
The solid state relay required an input signal of 3 volts to 8 volts. I chose an AC adapter with a 7 volt DC output which turned out to be just enough for the job. A few volts more would not have hurt.
When you plug a modular phone cord into the Line jack on the back of the phone base, the two middle wires (usually color coded red and green) are the two that connect to the phone line. When the phone is not in use, these two wires present a high impedance to the phone line. That is, in DC terms there is a very high resistance between them. When you press the Talk button on the phone handset, these two wires present a much lower impedance to the phone line which, in DC terms, is a fairly low resistance. We can use this characteristic to control an external circuit even when it is not a telephone line. Generally speaking, these two wires (red and green) are not polarity sensitive and can be used interchangeably.
In the schematic, you can see that the DC output from the AC adapter will be applied to the DC control input of the solid state relay if the phone base conducts. That will turn on the solid state relay and the lamp will be lit.
Once everything is interconnected, plug in the phone base's own AC adapter, the plug for the lamp circuit, and the AC adapter that powers the solid state relay. Also plug in the separate charging station for the phone handset. After the handset has had a chance to charge well, you may have to place the handset into its position in the phone base so that it can sync up with the phone base. This only takes a few seconds. Then remove the handset, press the Talk button and the lamp should illuminate. Pressing the End button on the handset or just placing the handset into its own charging station will cause the lamp to be extinguished.
Later, we wanted to add a third handset in yet another room. The easiest way to do it was to buy a three-handset system so we replaced the whole setup, locating the third handset and its respective charger in the new room.
I boxed up the old two-handset phone system and set it aside.
One day, we decided we wanted to have a lamp that we could control from a remote location. There was power available where the lamp was to be located but there were no easy ways to provide a control signal. I considered an X-10 control system which delivers control signals through the power wiring but I am cheap and so I look for ways to do things without spending money.
I pondered the idea of how difficult it would be to use the spare wireless phone system to do the job and it turned out to be surprisingly easy. Basically, I just needed to add an AC adapter to provide a source of DC power, a solid state relay, a modular phone plug to fit the phone base, and the wiring for the lamp.
The schematic shows how I connected everything.
The solid state relay required an input signal of 3 volts to 8 volts. I chose an AC adapter with a 7 volt DC output which turned out to be just enough for the job. A few volts more would not have hurt.
When you plug a modular phone cord into the Line jack on the back of the phone base, the two middle wires (usually color coded red and green) are the two that connect to the phone line. When the phone is not in use, these two wires present a high impedance to the phone line. That is, in DC terms there is a very high resistance between them. When you press the Talk button on the phone handset, these two wires present a much lower impedance to the phone line which, in DC terms, is a fairly low resistance. We can use this characteristic to control an external circuit even when it is not a telephone line. Generally speaking, these two wires (red and green) are not polarity sensitive and can be used interchangeably.
In the schematic, you can see that the DC output from the AC adapter will be applied to the DC control input of the solid state relay if the phone base conducts. That will turn on the solid state relay and the lamp will be lit.
Once everything is interconnected, plug in the phone base's own AC adapter, the plug for the lamp circuit, and the AC adapter that powers the solid state relay. Also plug in the separate charging station for the phone handset. After the handset has had a chance to charge well, you may have to place the handset into its position in the phone base so that it can sync up with the phone base. This only takes a few seconds. Then remove the handset, press the Talk button and the lamp should illuminate. Pressing the End button on the handset or just placing the handset into its own charging station will cause the lamp to be extinguished.