Question 9.6: You want to switch 110 or 240V AC using a Raspberry Pi....
You want to switch 110 or 240V AC using a Raspberry Pi.
Use a PowerSwitch Tail II (see “Modules” on page 381). This handy device makes it really easy to switch AC equipment on and off from a Raspberry Pi. It has an AC socket on one end and a plug on the other, like an extension cable; the only difference is that the control box in the middle of the lead has three screw terminals. By attaching terminal 2 to GND and terminal 1 to a GPIO pin, the device acts like a switch to turn the appliance on and off.
You can use the same Python code as you did in Recipe 9.1 to use the PowerSwitch Tail, as shown in Figure 9-7.
Discussion
The PowerSwitch Tail uses a relay, but to switch the relay, it uses a component called an opto-isolator that has an LED shining onto a photo-TRIAC (a high-voltage, lightsensitive switch); when the LED is illuminated, the photo-TRIAC conducts, supplying current to the relay coil.
The LED inside the opto-isolator has its current limited by a resistor, so that only 3 mA flows through it when you supply it with 3.3V from a GPIO pin.
See Also
For switching DC using a power MOSFET, see Recipe 9.7, and for switching using a relay on breadboard, see Recipe 9.5.
A 240V version of the PowerSwitch Tail is available as a kit.
| Table A-8. Modules | |
| Raspberry Pi camera module | Adafruit: 1367, MCM: 28-17733, CPC: SC13023 |
| Arduino Uno | SparkFun: DEV-11021, Adafruit: 50, CPC: A000066 |
| Level converter, four-way | SparkFun: BOB-11978, Adafruit: 757 |
| Level converter eight-way | Adafruit: 395 |
| LiPo boost converter/charger | SparkFun: PRT-11231 |
| PowerSwitch tail | Adafruit: 268 |
| 16-channel servo controller | Adafruit: 815 |
| Motor driver 1A dual | SparkFun: ROB-09457 |
| RaspiRobot board | Sparkfun: KIT-11561, raspirobot.com |
| PiFace digital interface board | MCM: 83-14472, CPC: SC12827 |
| Humble Pi | MCM: 83-14637, CPC: SC12871 |
| Pi Plate | Adafruit: 801 |
| Gertboard | MCM: 83-14460, CPC: SC12828 |
| Breakout board with paddle terminals | MCM: 83-14876, CPC: SC12885 |
| PIR motion detector | Adafruit: 189 |
| Venus GPS module | SparkFun: GPS-11058 |
| Methane sensor | SparkFun: SEN-09404 |
| Gas sensor breakout board | SparkFun: BOB-08891 |
| ADXL335 triple-axis accelerometer | Adafruit: 163 |
| 4×7-segment LED with I2C backpack | Adafruit: 878 |
| Bicolor LED square-pixel matrix with I2C backpack | Adafruit: 902 |
| PiLite interface board | Ciseco, CPC: SC13018 |
| aLaMode interface board | Makershed: MKWY1, Seeedstudio: ARD10251P |
| Freetronics Arduino LCD shield | www.freetronics.com |
| RTC module | Adafruit: 264 |
| 16 x 2 HD44780 compatible LCD module | SparkFun: LCD-00255, Adafruit: 181 |
