♪ Hot dog ♪
We've grilled hot dogs using line voltage
on other demos to show the dangers of unisolated high voltage.
In this demo, we’ll show a controlled,
isolated hot-dog electrocutor.
It’s still dangerous,
and there are better ways to cook a hot dog,
but the circuitry is important for applications such as
battery charging and motor control.
A rectifier and capacitor
convert AC line voltage to approximately 170 volts DC.
A silicon carbide FET modulates the voltage to the load.
We left high-voltage wiring and the hot dog itself exposed
so you can see what’s going on.
We don’t recommend that.
The Variac is for soft start, since it’s not a good idea
to connect circuitry like this directly to line voltage.
We’re planning to add
an isolated solid-state soft start on future versions.
A non-contact current sensor evaluation board
measures the current drawn by the hot dog.
Cooking is controlled by an Arduino.
On the shield, an isolator protects the Arduino
from the high voltage,
and one of our DC-to-DC convertors provides isolated power
to drive the FET.
This isolator can drive some FETs directly,
but for this FET we have a separate gate driver.
There’s also a beeper to signal when the hot dog is done.
Let's start it up.
The cooking power starts high;
then decreases to avoid burning.
The profile is defined in the Arduino.
Here’s the rest of the Arduino program:
The setup routine...
We cycle through the cooking stages…
Here we power the FET,
and measure the hot dog current with the GMR current sensor.
The circuit-breaker routine, that protects against overcurrent.
And the display routine.
Here's the schematic:
The DC-to-DC convertor
provides an isolated five-volt supply to power the isolator
and an isolated nine-volt gate supply.
[Three beeps]
It’s perfect!
The current sensor provides
overcurrent protection.
It kicks in if we overcook the hot dog.
[Long beep]
So we’ve demonstrated isolated power control
and overcurrent protection for added safety.
Future safety enhancements we’re planning include:
• AC soft start;
• An enclosure interlock; and
• A temperature sensor.
These are the key parts in this demo:
IL600-Series isolators have:
• best-in-class Common-Mode Transient Immunity;
• an extended three to 6.6-volt power supply range
for full direct-drive of six-volt MOSFET gates;
• full isolation;
• no input-side power supply;
• and ultraminiature packages.
Key ILDC-Series DC-to-DC convertor specifications are:
• various output voltages--
we used the five-volt version in this demo;
• soft start--
so the microcontroller can start before the FET is powered;
• best-in-class isolation;
• the full industrial temperature range;
• and a DFN version that’s the world’s smallest isolated DC-DC convertor.
Click, email, or call for more information.
Our engineers would “relish” a chance to “ketchup” on your requirements.