APC7921 overview
Ethernet w activity-leds
Serial
2x 7-segment display
1x 3-color LED
Button
factor-reset-switch (hole)
8x female outlets
8x leds
1x male inlet
FRONT
+---------------------------------------------------+-----+
| Controller | | | |
+-------------+ | Relay board | |
| IN OUT |J131 J132 | |
| +-----------------------------------+ |
| +-----------------------------+ |
| | PSU Board | |
| |J231 J266 | |
+---------------------+-----------------------------+------
BACK
PSU overview:
PSU -> PSU -> controller wiring
10-wire flat-cable with 2mm pitch 2x5 connectors runs from J266->J231->Controller-IN
See connector J266 and J231
The PSU board has two identical PSU's onboard that provide 24VDC
The right-most PSU also has a set of pins used for connecting current-transformer circuitry to the controller.
The left-most PSU only has 2 pins connected for 24VDC, nothing else.
Controller overview:
The controller provides ethernet and serial connectivity; as well as a 2-digit display and a 3-color status-led to indicate errors and/or amperage. It also has a single button to interact with the device, as well as a pin-hole switch that allows for factory-resets.
Main things to replicate:
- 24VDC 'merging'
- Faulty PSU detection
- Ethernet function
- Serial function (if desired)
- 24VDC->3.3VDC conversion (for relay-board logic)
- I2C bus to control relay-board
- Adress-bus lines (can be hard-wired)
The controller drives the relay-board with a similar 10-conductor flatcable with 2x5pin 2mm headers.
It provides 24VDC and 3.5VDC power to the relay-board with seperate GND's.
It also provides an I2C bus (SDA/SCL) and 3 'address-lines'.
See connector J131
Relay board:
There are 2 main parts to the relay-board. The IO-logic and the relay-logic.
Relay-board IO logic:
The relay-board uses a PCF8574 'Remote 8-Bit I/O Expander for I2C Bus' to provide 8 outputs that drive the relays.
It is powered with 3.5VDC from the controller-board which creates it from the 24VDC available there.
The PCF85674 has 3 address-strapping lines A0,A1,A2 that allow selecting the I2C slave-addresses for both READ or WRITE operations. See table later in the document.
In single-board operation, strapping all pins to L would put the READ address at 0x41 and WRITE at 0x40
The relay-boards can be daisy-chained by connecting a next board to the J231 of the first.
For this to work, however, at least one, and at most two, address-lines will need to be strapped H
The reason for this is the manner in which the A0-A2 lines are presented on the J231 connector. They are shifted one pin,
Signal J131 +-------------+ J132
A0 7 ---------|---------+ +------ 7
A1 9 ---------|--+ +---------- 9
A2 10 ---------+ +----------------- 10
The PCF8574 provides 8 outputs that drive the relays using a circuit that first INVERTS the data via a NOR port (one pin strapped to ground, the other connected to the PCF8574) before running to one of the 8 relay-circuits that switch the 220VAC power provided to one of the 8 output terminals.
The 8 NOR ports for this setup are provided by 2x 7402 IC's and seem to function both as a signal-conditioner as well as a way to ensure the power-on state is 'on' for each of the relay circuits (needs to be verified).
Relay-board relay circuit:
Each of the 8 relay-circuits is identical and consists of:
- A small switching-transistor driven from a NOR-gate, switching 24VDC
- A Relay-coil being driven by the switching-transistor
- A flyback diode across the relay in reverse-polarity for circuit-protection
- An ESD-protection diode ( -->|-+->|-- ) that is employed to help drive an LED
|
- An LED
- A series resistor to current-limit
------- Connector pinouts-----------
J266 (right, next to current-transformers) PSU1
+----+
|10 9|
|8 7|
|6 5|
|4 3|
|2 1|
+----+
1 Sense Phase C
2 Center of 3phase
3 Sense Phase A
4 Center of 3phase
5 24VDC PSU1
6 24VDC PSU1
7 Sense Phase B
8 GND PSU 1
9
10
J321 (left, on edge of board) PSU2
+----+
|10 9|
|8 7|
|6 5|
|4 3|
|2 1|
+----+
1
2
3
4
5
6
7
8
9 GND PSU 2
10 24VDC PSU2
Note: GND PSU1 and GND PSU2 are connected together via screws that fasten PCB to chassis.
J131 on relais PCB INPUT
+----+
|1 2|
|3 4|
|5 6|
|7 8|
|9 10|
+----+
J131 PCF8574
1 GND IO 8
2 GND relais
3 VCC IO 16
4 SDA IO 15
5 24VDC relais
6 24VDC relais
7 A0 IO 1
8 SCL IO 14
9 A1 IO 2
10 A2 IO 3
J132 on relais PCB , Daisychain OUTPUT
1 GND IO
2 GND Relais
3 VCC IO
4 SDA IO
5 24VDC RELAIS
6 24VDC RELAIS
7 A2 IO
8 SCL IO
9 A0 IO
10 A1 IO
PCF 8574 DW (16 pin)
+----------+
A0 -| 1 * 16 | VCC (2.5-6vdc)
A1 -| 2 15 |- SDA
A2 -| 3 14 |- SCL
P0 -| 4 13 |- _INT_
P1 -| 5 12 |- P7
P2 -| 6 11 |- P6
P3 -| 7 10 |- P5
GND -| 8 9 |- P4
+----------+
