The Triacs Power Control module drives 8-triacs using a pulse width
modulation system and a zero crossing detection module. The system
is driven by a 68HC11 in bootstrap mode and connected to boot from
its internal eeprom.
This board was first tested using an Ada95 program that was uploaded
using the bootstrap mode. The program was less than 250 bytes.
http://gel.sourceforge.net/ada_example.php.
| Zero Crossing Detection |
|
The zero crossing detection is composed of diodes and resistors and
notifies the 68HC11 on port A (A0 and A1) when the mains changes of
polarity. The 68HC11 is notified a few microseconds before and a few
microseconds after.
|
| Triac Control |
|
Each triac is driven by an ULN 2003 driver. The driver creates a negative
pulse on the triac gate. The 68HC11 generates pulses on its port B outputs.
The pulses are generated by software and by taking into account the
zero crossing detection (inputs A0 and A1).
|
| Fuse Detection |
|
The 8 inputs of 68HC11 port C are used to detect that the fuses associated with
each triac are not broken.
|
| Remote Control |
|
The system is controlled remotely through the serial line. It accepts
simple commands to turn on or off a given triac as well as to give
feedback and global status. It can report periodically the temperature
of the triacs cooler as well as the global current consumption.
|
| System Isolation |
|
The 68HC11 is directly connected to the mains. The remote control port
is isolated by three opto-couplers.
|
Documentation on the chips used by PC Power Triacs board.
(1) Documentation publicly available on various constructor
web sites and copied here for archiving.
|
