Power consumption measuring unit

From uCtrl.net

Complete, connected

PCMU, driven by AVR ATTiny2313.

Information

• YouTube video

You need a light sensor that registers LED flashes from your house power consumption unit. In Norway we have a unit that emits a LED flash every X kW. This sensor connects to the module. The consumption is measured in kW and calculated by counting the number of pulses and divide by 500 (500 pulses pr. kW). The registration will continue as long as the module receives a signal from the light sensor, the used amount can then be read using serial communication from the computer.

Two values are stored, current and present usage. By sending a command to the module the current value can be moved to the previous, thus making it possible to compare periods. Current usage value is deleted when moved to previous. These values are stored in EEPROM every hour, and is used when the module start up from e.g. a power loss. That means that you could lose one hour of monitoring. You can also enter a desired start usage value.

Before any EEPROM values are stored the module will display -1 kW current and previous usage. There can be reset by moving current to previous two times (command 4). Correct EEPROM values will then be stored one hour after first received signal.

Connectors

Power connector

2,5 mm, 9-12V=, positive center.

9-pin Sensor

• 6 : 5V + out
• 7 : 5V - out
• 8 : 5V + sensor in
• 9 : 5V - sensor in

9-pin RS-232

• 2 : Transmit
• 3 : Receive
• 5 : GND

Communication

Forbruksmaaler v.1.0                                                           
JensenCorp 0704001                                                             
                                                                               
Press 0 for help                                                               
                                                                               
1 - Current usage                                                              
2 - Previous usage                                                             
3 - Enter starting point                                                       
4 - Move current to previous                                                   
                                                                               
Current usage will be deleted! (0 to cancel)                                   
Enter starting point in kW : 100                                               
100 kW saved                                                                   
100 kW current usage (50000 pulses)                                            
100 kW moved to previous                                                       
100 kW previous usage                                                          
0 kW current usage (0 pulses)

Serial settings

Baud

9600

Data bits

8

Parity

None

Stop bits

1

Parts list

Sensor not included.

Images

Inside

Inside complete

Complete

Complete, connected

Schematic drawing

Resources

• MAX202
• RS-232

Source code

The program is written in basic, using Bascom-AVR.

 '--------------------------------------------------------------
'                         Thomas Jensen
'--------------------------------------------------------------
'  file: AVR_FORBRUKSMÅLER_v.1.0
'  date: 27/04/2007
'--------------------------------------------------------------
$regfile = "attiny2313.dat"
$crystal = 8000000
$baud = 9600
Config Portb.0 = Input
Config Portb.1 = Output
Config Portb.2 = Output
 
 
Dim Serialcharwaiting As Byte , Serialchar As Byte
Dim Is_active As Bit , W As Long , Kw As Long
Dim Lifesignal As Integer , Led_timer As Integer
Dim Set_kw As Long , Kw_prev As Long , Pval As Integer
Dim Eeprom As Eram Long , Eeprom2 As Eram Long , Eeprom_timer As Integer
 
Print "Forbruksmaaler v.1.0"
Print "JensenCorp 0704001"
Print
Print "Press 0 for help"
Print
 
Kw = Eeprom
W = Eeprom * 500
Kw_prev = Eeprom2
 
Top:
Serialcharwaiting = Ischarwaiting()
 
If Serialcharwaiting = 1 Then
   Serialchar = Inkey()
      Goto Myroutine
   End If
 
Goto Main
 
Myroutine:
Select Case Serialchar
Case 49
Print Kw ; " kW current usage (" ; W ; " pulses)"
Case 50
Print Kw_prev ; " kW previous usage"
Case 51
Goto Set_value
Case 52
Goto Reset_value
Case 48
Print "1 - Current usage"
Print "2 - Previous usage"
Print "3 - Enter starting point"
Print "4 - Move current to previous"
End Select
 
 
 
Main:
'count
If Pinb.0 = 0 And Is_active = 0 Then
   Is_active = 1
   Incr W
   Kw = W / 500
   Led_timer = 51
   If Eeprom_timer = 0 Then Eeprom_timer = 1801
   End If
If Pinb.0 = 1 Then Is_active = 0
 
'led_timer
If Led_timer > 0 Then Decr Led_timer
If Led_timer = 50 Then Portb.2 = 1
If Led_timer = 0 Then Portb.2 = 0
 
'lifesignal
If Lifesignal > 0 Then Decr Lifesignal
If Lifesignal = 500 Then Portb.1 = 1
If Lifesignal = 0 Then
   Portb.1 = 0
   If Eeprom_timer > 0 Then Decr Eeprom_timer
   If Eeprom_timer = 1 Then
      Eeprom = Kw
      Eeprom2 = Kw_prev
      End If
   Lifesignal = 2001
   End If
 
Waitms 1
Goto Top
End
 
Set_value:
Print
Print "Current usage will be deleted! (0 to cancel)"
Input "Enter starting point in kW : " , Set_kw
If Set_kw = 0 Then
   Print "Operation aborted"
   Goto Main
   End If
W = Set_kw * 500
Kw = Set_kw
Print Kw ; " kW saved"
Goto Main
End
 
Reset_value:
Kw_prev = Kw
Kw = 0
W = 0
Print Kw_prev ; " kW moved to previous"
Goto Main
End