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低成本电动控制使用可控硅

资料介绍
INTRODUCTION
Most countertop cooking appliances like electric
ranges, skillets and fryers have an adjustable mechan-
ical thermostat to vary the heat output of the range.
This solution is inexpensive, but there are several
drawbacks to mechanical thermostats:
• Mechanical thermostats have to be calibrated at
the factory.
• They have poor simmer performance (control is
not precise at low temperatures).
• The accuracy of these devices is poor.
• Mechanical components wear out over time.
This application note will describe a low-cost microcon-
troller-based replacement for the mechanical thermo-
stat which eliminates these drawbacks. The
PIC10F204, Microchip's 6-pin PICmicro
®
microcontrol-
ler (SOT-23 package), is used to implement this
solution. The PICmicro gathers user inputs from a
potentiometer and controls current to the heating
element via a triac. This application note will discuss
triac theory, so it is also a good resource for other appli-
cations that interface to AC lines (i.e., light switches,
vacuum cleaners and various other household
appliances). Power to the PICmicro is supplied directly
from the AC lines via a resistive power supply.
Compared to the mechanical thermostat, the
PIC10F204 solution offers design flexibility, including
the addition of user-friendly features. Two such
features are incorporated into the PICmicro solution
detailed here. These features are: (1) a status LED
indicating the range is on or off, and (2) an automatic
shutdown. The automatic shutdown provides added
safety by shutting the range off after 2 hours if it is left
unattended.
AN958
Low-Cost Electric Range Control Using a Triac

Author: Reston Condit
MECHANICAL THERMOSTAT
Microchip Technology Inc. OPERATION
Electric ranges create heat by applying the AC line
voltage across a resistive heating element. An adjust-
INTRODUCTION able mechanical thermostat in series with the heating
element has a rotary dial which sets the amoun……
低成本电动控制使用可控硅
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