Input Noise

[PJALM]

Hi Sean,

Did you have your PIC reset itself or do any unusual things?

All my inputs are interrupt driven, maybe this is also a problem.

I am going to try changing it to a PIC18F452 to see if it helps.

Thanks.

[Bruce]

What would be the easiest way to build the circuit with a separate power supply for the optos yet still only have one PCB

Just design your board with two separate power planes, and power supply
input terminals.

Separate DC power supply's input to two separate regulators on the same
PCB.

|..P.S. input A.............P.S. input B]
|--[+-]------------------[+-]-----|
|..PIC side........<..out.[]..input..<..| AC connections on outer edge
|.....................<..out.[]..input..<..| optos in center of board close
|..one PCB........<..out.[]..input..<..| to controller ins/outs

TIPS:

Keep AC traces (if any) as short as possible, and located on the far edge
away from the controller side of the board.

Make the bottom layer under the "controller side" a large ground plane with
decoupling caps at all power connection points.

Do not cross-over traces from one side to the other. Noise will couple from
one PCB trace to another right through your PCB substrate.

If you have any mechanical relays on either board, consider MOV's (metal
oxide varistors) across the relay contacts to snub contact spark/discharge.

I've done a number of boards like this without any glitches. All for large
motors & heavy appliances being controlled or monitored by the PIC.

Im my experience, I've noticed that all of the 18F series and most 16F "A"
series are all more succeptible to noise than older non "A" series 16F parts.

a mind of its own and randomy turns on relays, outputs serial data, resets itself etc

That definitely sounds like a serious noise problem, but it may also be the
input you're using. Does it throw a fit if you connect this same input to
any other signal?

Which input are you using?

[PJALM]

I am using PORTB.0 for the encoder, i am using interrupts to capture the pulses.

The relays do not control the motor directly but instead drive an AC Drive Inverter which creates the 3 Phase 330V AC required by the motor. The relays are the G5V-1 micro relays and are being driven by a ULN2003.

[Bruce]

Interrupts alone can cause seriously erratic behaviour depeding on your
program structure & how you're handling things getting in/out of the int
handler.

I would still look at isolation, but it may also have something to do with your
interrupts. Can you post your interrupt handler?

[PJALM]

Here is the interrupt handler:

'-------------------------------------------------------------------------------
' Interrupt Handler
'-------------------------------------------------------------------------------
    DISABLE INTERRUPT                        ' No interrupts past this point
Main_Interrupt_Handler:

    '---------------------------------------------------------------------------
    ' PortB.0 Interrupt, Motor RPM Counter
    '---------------------------------------------------------------------------
	IF INTCON.1 = 1 THEN
        IF Calibrating = 1 THEN
            Total_Pulses = Total_Pulses + 1
        ELSE
            IF System_Calibrated = 1 THEN
                New_Position_Counter = New_Position_Counter + 1

                IF New_Position_Counter >= (Pulses_Per_Position + Temp_Pulses) THEN
                    SELECT CASE Current_Direction
                        CASE Forward_Dir
                            Current_Position = Current_Position + 1
                            IF Current_Position > Total_Positions THEN
                                Current_Position = 1
                            ENDIF
                        CASE Reverse_Dir
                            Current_Position = Current_Position - 1
                            IF Current_Position = 0 THEN
                                Current_Position = Total_Positions
                            ENDIF
                    END SELECT

                    DEBUG 13, 10, "[ Position Change ] Current Position: ", DEC Current_Position, 13, 10
                    
                    New_Position_Counter = 0
                    Temp_Pulses = 0
                ENDIF
            ENDIF
        ENDIF
            INTCON.1 = 0
	ENDIF 
    '---------------------------------------------------------------------------


        
    '---------------------------------------------------------------------------
	' PortB.1 Interrupt, Position 1 Sensor
    '---------------------------------------------------------------------------
	IF INTCON3.0 = 1 THEN
        DEBUG 13, 10, "[ INTERRUPT ] Home Position Detected", 13, 10
            Pos1Found = 1
            New_Position_Counter = 0
            Temp_Pulses = 0
            Current_Position = 1
	    INTCON3.0 = 0
	ENDIF
    '---------------------------------------------------------------------------



    '---------------------------------------------------------------------------
    ' PortB.2 Interrupt, Fault Relay Input
    '---------------------------------------------------------------------------
    IF INTCON3.1 = 1 THEN
        DEBUG 13, 10, "[ INTERRUPT ] AC Invertor Fault Detected", 13, 10
        AC_Fault_Detected = 1
        INTCON3.1 = 0
    ENDIF
    '---------------------------------------------------------------------------
    


    '---------------------------------------------------------------------------
    ' USART Receive Interrupt
    '---------------------------------------------------------------------------
    IF PIR1.5 = 1 THEN
        'DEBUG 13, 10, "[ INTERRUPT ] USART Receive", 13, 10

        HSERIN [RS485_B0]

        SELECT CASE RS485_B0
            CASE RS485_STX
                RS485_Receiving_Data = 1
                RS485_Bytes_Received = 0
                FOR i = 1 TO RS485_Buffer_Size
                    RS485_Data_Buffer[i] = 0
                NEXT
                
            CASE RS485_ETX
                RS485_Receiving_Data = 0
                
                RS485_To_Address = RS485_Data_Buffer(0)
                RS485_Command = RS485_Data_Buffer(1)
                RS485_Parameter.HighByte = RS485_Data_Buffer(2)
                RS485_Parameter.LowByte = RS485_Data_Buffer(3)
                RS485_From_Address = RS485_Data_Buffer(4)
                
                RS485_Parameter = RS485_Parameter - 10
                
            CASE ELSE
                IF RS485_Receiving_Data = 1 THEN
                    RS485_Data_Buffer(RS485_Bytes_Received) = RS485_B0
                    RS485_Bytes_Received = RS485_Bytes_Received + 1
                ENDIF
        END SELECT
        PIR1.5 = 0
    ENDIF
    '---------------------------------------------------------------------------

        
IntDone:
	RESUME					' Return to main program
    ENABLE INTERRUPT
'-------------------------------------------------------------------------------

[Bruce]

This looks OK to me except for PIR1.5 = 0.

The USART receive interrupt flag bit can only be cleared by reading RCREG
until the buffer is empty. You're reading this only once in your int handler.

If you receive more than a single byte of data it can cause problems. I would
test the flag again before exiting this particular int handler sub-routine.

I don't think this is causing the problem you're seeing, but it could be one if
you're expecting PIR1.5 = 0 to clear the USART interrupt flag.

What happens if you remove the encoder, and replace it with a push-button
switch?

Does pressing the switch to simulate the encoder logic on the int0 input pin
work?

If it works then I would have to suspect an isolation problem.

[PJALM]

Bruce, putting the switch works fine so I also suspect its an isolation problem. I am going to try your sujestions and build a second power supply.