Overview

This is a new project I'm starting. I want to control the electrical power of all computers and peripherials I'm using. It will have 3x 68HC11 organized as follows:

• A first 68HC11 directly manages 8-triacs to control the mains of the local computers and peripherals (PC, screen, printer, scanner, modem, ...). It is directly connected to the 220V mains. It communicates with main 68HC11 using the serial line (opto-isolated). The program will be in the 512-byte EEProm.

• A second 68HC11 controls the remote pheripherals. It is intended to control the mains of a Sun3, a remote PC server, a noisy hard disk, ... (well, few noisy boxes). It communicates with the main 68HC11 using the SPI.

• The third 68HC11 controls everything and gives orders to the above. It is connected to the local PC using the serial line. For the user interface, I'm thinking about the Touch LCD Panel.

In addition to these, 4 separate 9V supplies will be available. Two of them will be used for power supply of my Axiom Manufacturing boards.

Triacs Board

Validated the board layoutBoard manufacturedBoard finishedBoard tested 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. GEL Ada95 Example.

Triacs Power Control Module

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.

Triacs Power Control Module

Documentation on the chips used by PC Power Triacs board.

Documentation (1)
M68HC11E
68HC11E1

L7800 Positive voltage regulator (7805, 7812, 7815, ...). BC237 NPN Epitaxial Silicon Transistor BT137.pdf Triacs (I've used a BT137-600). Transformer (Myrra). TL072 Low Noise Dual J-FET Operational Amplifiers MC34064 Undervoltage Sensing Circuit LM35 Precision Centigrade Temperature Sensors CNY17 TRIOS (R) Phototransistor Optocoupler MTC6 Dual Phototransistor Optocoupler ULN2804 Eight darlington arrays

<FONT SIZE="-3">(1) Documentation publicly available on various constructor web sites and copied here for archiving.<FONT SIZE="-3">