Capacitance Touch Glass - Electrolux 30" Service Manual

How the PRC Glass touch electronic oven control
works:
The PRC glass touch electronic oven control system is
made up of four parts that control the bake and broil
elements, the convection fan in the oven, oven light, and
the locking of the door in clean.
1. Electronic oven control.
2. Glass touch panel
3. Oven temperature sensor.
4. Oven door lock mechanism.

Capacitance touch glass:

The capacitance touch glass is used to allow user to
input command to the electronic control board. Metal
plates that form capacitors are fasten to the back of the
glass behind each input touch areas designed on the
glass and connected to the electronic control board by
a ribbon. The microprocessor reads the capacitance of
the capacitors. When the glass is touched in the
indicated area the capacitance changes giving an input
to the control board.
Preheat:
When the preheat pad is touched and a temperature is
entered with the number pads, the bake relay and the
double line break relay on the board closes, and apply
electrical power bake element. "PRE" and "BAKE"
appear in the display.
disappears and the oven operates as in normal bake.
Bake:
When the bake pad is touched, and a temperature is
entered with the number pads, the bake relay on the
board closes, and connects one side of the line to the
bake element. "BAKE" appears in the display. In the tip
of the oven sensor is a positive thermistor that increases
in resistance as the oven temperature increases. The
EOC microprocessor reads the resistance of the oven
sensor, and compares it with the programmed temperature
set into the control. When the resistance of the oven
sensor indicates temperature in the oven is about 10
degrees above the programmed temperature, the
microprocessor opens the relay, which removes power
from one side of the element. When power is removed
from the element the oven temperature begins to lower.
As the oven temperature lowers the resistance of the
oven sensor decreases. When the oven drops to about
10 degrees below the programmed temperature, the
resistance of the sensor tells the microprocessor to
After the first cycle "PRE"
close the relay contacts, and once again provide power
to the element. After the first cycle and whenever the
oven calls for heat, the EOC cycles the broil element on
for seven seconds and then the bake element on for fifty
three seconds out of every minute. This provides top heat
during the bake cycle. The two elements are never on at
the same time.
NOTE: Oven controls may have a temperature swing of
more or less than 20 degrees. The important
thing is the average temperature in the oven.
The average temperature in the center of the
oven should be within 10 degrees of the
programmed temperature.
Timed bake:
The timed bake function allows the oven to be programmed
to stop bake at a set time, or to delay the start and stop
baking at a set time. The stop time cannot be set for
more than 11 hours and 59 minutes ahead of the time of
day.
Convection bake:
When the convection bake pad is touched and a
temperature is set, two things happen that do not happen
in normal bake. The EOC automatically lowers the oven
temperature 25° F below the temperature that was
manually set in the control. If the oven door is closed, the
convection relay on the EOC closes, providing line to
neutral voltage to the convection fan motor and the
convection assist element. This relay remains closed
until the program is canceled or is interrupted by the
opening of the oven door. If interrupted by the opening of
the oven door, the relay will automatically close when the
door is closed.
Convection roast:
Convection roast operates the same as convection bake
except the control does not operate below the set
temperature and the temperature differential is larger.
Broil:
When the broil pad is touched, and a temperature is
entered with the numbers between 450° F and 550° F
(usually 550° F), the broil relay on the board closes, and
connects one side of the line to the broil element. In the
tip of the oven sensor is a positive thermistor that
increases in resistance as the oven temperature
increases. The EOC microprocessor reads the resistance
of the oven sensor, and compares it with the programmed
temperature set into the control. Usually you do not want
the broil element to cycle so the oven door is opened to
the broil stop position. If the door is not opened the broil
94