RPI LCT4V3 stack with RPI LCT8 application example
We will showcase an application example of stacking together a RPI_LCT4V3 with a RPI_LCT8.
Mechanical considerations
The use of screw terminal connectors on RPI_LCT4V3 and RPI_LCT8 makes stacking challenging.
We are proposing here a solution using free plug connectors on the master board. These allow access to the bottom board connector and clearance to access the top board.
This is a solution for 2 boards stack. One master plus one slave. There is no options for stacking 3 boards or more at the moment.
Master RPI_LCT4V3
The master board RPI_LCT4V3 with the free plug connector is shown below:
Slave RPI_CT8
The slave board RPI_CT8 with standard screw terminals is shown below.
2 boards stack
The combined stacking is shown below. Offering 3 Voltage ports and 12 Current ports.
Configuration
Here is a configuration example for a four 3-phase systems being supplied by the same line. The CT port will be associated as follow.
CT1 to CT4 on Master -> Phase 1 against V1 CT1 to CT4 on Slave -> Phase 2 against V2 CT5 to CT8 on Slave -> Phase 3 against V3
We plan to just display RealPower and Vrms.
We generate the configuration using the web tool as below.
[main] format = 3 nodeid = 11 polling = 5000 vest = 240.0 xpFREQ = 50 Ncycle = 20 kcal = 333.33 333.33 333.33 333.33 333.33 333.33 333.33 333.33 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 545.0 545.0 545.0 1 333.33 333.33 333.33 333.33 phasecal = 0 Nnode = 12 Nchan = 15 HWSCT = 7 7 3 6 6 2 5 5 1 4 4 0 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 HWMCPSCT = 10 6 6 10 6 6 10 6 6 10 6 6 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 HWVOL = 2 1 0 2 1 0 2 1 0 2 1 0 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 HWMCPVOL = 10 10 10 10 10 10 10 10 10 10 10 10 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 CHTYPE = 1 1 1 1 1 1 1 1 1 1 1 1 3 3 3 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 CHID = 0 1 2 3 4 5 6 7 8 9 10 11 0 1 2 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 debug = 0
Running the configuration using debug = 1 reports a full scan interval of 4870ms. Polling of 5000ms is therefore well adequate. This could be reduced if opting for a number of cycles lower than the default 20.
Run time
With the above configuration the cat commands returns the following stream:
pi@raspberrypi:~ $ cat /dev/ttyAMA0 11 1.6 2.8 -0.5 -3.9 45.2 -0.1 -2.3 -0.0 0.7 -0.7 0.9 2.6 233.7 234.0 233.0 11 2.7 11.5 -7.5 -4.2 36.4 -7.3 -2.5 0.1 -2.5 -5.8 0.9 1.0 233.2 234.0 233.2 11 -0.5 5.1 -4.8 -9.5 18.8 -4.7 -7.9 0.1 -5.8 -8.7 0.9 -4.1 233.3 233.9 232.9 11 -5.2 5.5 -4.8 -2.9 3.1 -5.3 -12.1 0.0 -4.4 -8.8 0.5 -5.1 233.4 234.1 233.0
Only voltage is connected above. No load.
Using a simple python script we can output this in a pretty way.
#!/usr/bin/python2
import serial
ser = serial.Serial('/dev/ttyAMA0', 38400)
try:
while 1:
# Read one line from the serial buffer
line = ser.readline()
# Remove the trailing carriage return line feed
line = line[:-2]
# Create an array of the data
Z = line.split(' ')
# Print it nicely
print ("----------")
print (" \tP1\tP2\tP3\tP4\tVrms")
print ("L1:\t%s\t%s\t%s\t%s\t%s" % (Z[1], Z[4], Z[7],Z[10],Z[13]))
print ("L2:\t%s\t%s\t%s\t%s\t%s" % (Z[2], Z[5], Z[8],Z[11],Z[14]))
print ("L3:\t%s\t%s\t%s\t%s\t%s" % (Z[3], Z[6], Z[9],Z[12],Z[15]))
except KeyboardInterrupt:
ser.close()Which outputs on the display below on the terminal
---------- P1 P2 P3 P4 Vrms L1: 4.9 7.2 3.5 9.5 234.0 L2: 13.0 -7.7 -0.0 -0.1 234.8 L3: 5.3 5.8 6.2 7.4 233.6