Line-voltage based
hot dog cookers show how NVE components can be used for applications such as power
conversion, battery charging, and motor control. Hot dogs let us see and hear
power transfer.
We start with a bare hot dog directly connected to line voltage, and step-by-step
add safety and cooking enhancements.
Here is a playlist with the six demonstrations:
Uncontrolled
We show an uncontrolled, inherently dangerous
hot dog connected directly to line voltage.
Isolated FET control
A controlled version uses DC to power the hot
dog via a silicon carbide FET. We use an isolated FET driver and an isolated DC-to-DC
convertor to generate the gate-drive voltage. These circuits are extensible to
H-bridges. We added an electrical box for the hot dog.
Rectified AC
We eliminated the filter capacitor and used rectified
AC. This prevented startup surges and improved safety.
Temperature sensing
Next, we added a temperature sensor to ensure
the hot dog is cooked to a safe temperature. We used an isolator between the SPI
Smart Sensor and the controller because the sensor is in contact with the hot
dog and therefore in contact with high voltage. The isolator also functions as
a level shifter between the 3.3-volt sensor and a five-volt Arduino. The sensor
allowed us to cook to the USDA-recommended 140 °F.
Current sensing
A noncontact current sensor provides overcurrent
detection for improved safety. These sensors are high speed and inherently isolated.
The sensor also allowed a cooking algorithm based on total applied energy, so
we cooked hot dogs to a perfect 7 kilojoules.
Interlock switch
Finally, we add a GMR Switch and a magnet on the
cover to form an interlock, allowing power to be removed when the cover is open.
GMR Switches are ideal for this type of proximity sensing.
Schematic
The complete hot dog cooker schematic is here:
