PMDC SERVO MOTOR WITH quadrature encoder DRIVE ?

[phoenix_1]

Did any idea how to command PMDC SERVO MOTOR with quadrature encoder and after end of way stop in moment with no more movement ?
I need idea or sample of pulse diagram fro drive and stop conditions.
I dont need pbp source that part I will write...
Simple if I drive motor with PWM how to stop motor in moment and break it
electrical with no more movement to next move command ?
Maybe simultan change left right direction as break ???
I will use H bridge.
Regards and sorry for bad english.
Robert

[mackrackit]

Here are some threads talking about how to work with the encoder.
http://www.picbasic.co.uk/forum/show...rotary+encoder
http://www.picbasic.co.uk/forum/showthread.php?t=1552
http://www.picbasic.co.uk/forum/showthread.php?t=9700

As far as stopping goes...
Does the motor have a built in brake for holding? It can be stopped by shorting the leads but how fast it stops that way depens on the speed it is running when the leads are shorted.

[phoenix_1]

I was probe to stop motor and all work good.
But now I have another problem:
All examples from forum for read quadrature encoder with A and B outputs
at 5V are confused for my head, I was probe PBP examples but is to slow
and I think that for read quadrature encoder is needed ASM or some INT rutine becouse when motor work on ~ 3000 rpm rutine must be ultra speed
and background proces....
My head is like baloon ...

[phoenix_1]

All other info about my probe is now in PicBasicPro FORUM in:
Probe to read quadrature encoder with DT_INT need help
After my success I will post all here on FORUM.
If any help and good idea pls write.
Many thanks to all good peoples here!
Best regards Robert

[HenrikOlsson]

I recommend you take a look at the 18F2431 series PIC. It has a motion feedback module built in that can be set up to keep track of an incremental encoder. It also has a lot of other goodies specifically targeted at motor control applications.

/Henrik.

[phoenix_1]

I recommend you take a look at the 18F2431 series PIC. It has a motion feedback module built in that can be set up to keep track of an incremental encoder. It also has a lot of other goodies specifically targeted at motor control applications.

/Henrik.

I was buy today 18F4431 and will move to it.
At moment I looking for examples for it.
Thanks and regards Robert

[phoenix_1]

Here is success probe with count encoder from 0 to 2000 for one turn of shaft of motor.

' Pic 18F4431 @ 20MHz true XTAL
    define osc 20
    DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
    DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
    DEFINE HSER_SPBRG 64  ' 19200 Baud @ 20MHz, 0.16%
    DEFINE HSER_CLROERR 1 ' Clear overflow automatically
    ADCON0=0 'Turn of ADC
    ANSEL0=0 'Make Port A inputs Digital

    PortA = 0
    PortB = 0
    PortC = 0

    TRISA = %011100                'QEI pins as inputs.
    TRISB = %00000000
    TRISC = %10000000              'USART RX pin as input.

    QEICON=%11001100
    DFLTCON = %00111000            ' enable error filter for all capture inputs
    MAXCNTL = %11001111           'lowbyte = 207
    MAXCNTH = %00000111           'highbyte = 7 but after math: highbyte * 256 = 1792 + 207 = 1999
'QEICON = %00010100                   'Setup QEI, 4X mode, reset on index. 
    PosLow VAR BYTE                          'Storage for the low byte of encoder count
    PosHigh VAR BYTE                         'Storage for the high byte of encoder count
    PosTemp VAR BYTE                        'Temporary storage for low byte of encder count
    Position VAR WORD                      'Actual encoder position, 16bit word.
    POSCNTL = 0                            ' clear lowbyte of counter for start
    POSCNTH = 0                            ' clear highbyte of counter for start
CLEAR
    
Main:
    Gosub GetPosition
    HSEROUT [dec position]
    Pause 100
Goto Main

GetPosition:
'Since the position counter isn't double buffered we can get to situations
'where the lowbyte overflows between readings of the high and the low byte. This
'is prevented by reading the low byte two times and compare the two readings.
'If they are the same then we're fine, if not re-read the registers.
  
    PosHigh = POSCNTH                       'Get high byte of counter
    PosLow = POSCNTL                        'Get low byte of counter
    PosTemp = POSCNTL                       'Get low byte again
    
    If PosLow - PosTemp = 0 then Goto Done      'Compare, if equal we're done.
    
    PosHigh = POSCNTH                           'If not, get values again.
    PosLow = POSCNTL 

Done:
    Position = POSHIGH * 256 + PosLow           'Put high and lowbyte together.
RETURN
END

Will continue...
Robert

[phoenix_1]

Now little about PMDC breaking.
1.H-bridge drive of PMDC:

2.Slow DINAMIC break by short with same polarity of power supply.
Bad idea for fast servo PID control.

3.Fast RECUPERATIVE break good for PID control but must use high frequency of PWM.
The best is ~ 15-20KHZ.
Work for me good , but you need good DIODE in H-bridge for EMS breaking.

Thank's and regard's Robert