Recommendations - Model Train Controller

[malc-c]

Alain,

I'm getting way out of my depth here. I downloaded the three files from Darrel's web site (http://www.darreltaylor.com/DT_INTS-14/SPWM.html) and copied the sample code for the LEDs. Darrel stated on the PBgroup that the code Works on just about any chip. 12F, 16F, 18F, but if I try compiling with MCS I get errors, regardless of the target pic selected.

ERROR: variable wsave3 position request 416 beyond RAM_END 335

I've never used other include files etc before, but if I understand his site correctly it should be a simple matter of downloading and saving the three files to the PBP folder, copy and pasting the sample code into MCS and then compiling ?

Any ideas ?

[Acetronics2]

YESS

Big Idea !!! just comment the faulty line ... as this location only exist in elephant memory Pics !!!

also ... as stated in one of Darrel's further replies !!!

Alain

find it ... in the beginning of " DT int 14 .bas "

' --- IF any of these three lines cause an error ?? ----------------------------
' Comment them out to fix the problem ----
' -- It depends on which Chip you are using, as to which variables are needed --
wsave1 var byte $A0 SYSTEM ' location for W if in bank1
wsave2 var byte $120 SYSTEM ' location for W if in bank2
wsave3 var byte $1A0 SYSTEM ' location for W if in bank3
' ------------------------------------------------------------------------------

YOU DO NOT HAVE BANK3 in your Pic ... isn't it ???

[malc-c]

Alain, thanks for the life saving ring... its keeping me afloat

OK I have something that works... but its not as smooth as the PWM command in PBP.

This is the code, based on the sample taken from Darrel's website. Using a 12F675

@ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BODEN_ON

DEFINE OSC 4
CLEAR

DEFINE ADC_BITS 8	' Set number of bits in result
DEFINE ADC_CLOCK 3	' Set clock source (rc = 3)
DEFINE ADC_SAMPLEUS 50	' Set sampling time in microseconds

INCLUDE "DT_INTS-14.bas"            ; Base Interrupt System
INCLUDE "SPWM_INT.bas"              ; Software PWM module

DEFINE SPWM_FREQ  40                ; SPWM Frequency
DEFINE SPWM_RES   256               ; SPWM Resolution

D var byte

DutyVars   VAR BYTE[3]              ; DutyCycle Variables
  DutyVar1 VAR DutyVars[0]          ; group them in an array for easy access
  DutyVar2 VAR DutyVars[1]          ; with FOR loops etc.
  DutyVar3 VAR DutyVars[2]

ASM
SPWM_LIST  macro                    ; Define Pin's to use for SPWM
     SPWM_PIN  GPIO, 0, _DutyVar1  ; and the associated DutyCycle variables
     SPWM_PIN  GPIO, 1, _DutyVar2  ; Notice the underscore before variables
     SPWM_PIN  GPIO, 2, _DutyVar3
  endm
  SPWM_INIT  SPWM_LIST              ; Initialize the Pins
ENDASM

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  SPWMhandler,  ASM,  yes
    endm
    INT_CREATE                      ; Creates the interrupt processor
ENDASM

@ INT_ENABLE  TMR1_INT              ; enable Timer 1 interrupts

;_____________________________________________________________________________

Main:                               
 ADCIN 0, D 
    DutyVar3 = D   
GOTO Main

The output is quite pulsed, and moving the pot produces rather stepped increase in brightness rather than a smooth increase. Also the range of the brightness is limited to 2/3 the travel of the POT (unlike when I used the PWM command when it was right across from one end to the other)

The waveform is different to that previously found when using the PWM command, as can be seen by the two images attached (one low, one high)

I assume the PWM settings in Darrels code can be changed by altering the values of

DEFINE SPWM_FREQ  40                ; SPWM Frequency
DEFINE SPWM_RES   256               ; SPWM Resolution

I'll play with the values and see if anything improves - Thanks for your help on this

EDIT:
Changing the OSC to 20 and freq to 100 gives less flicker, but the transitions are still not smooth... I also think that I need to come up with some driver circuit for the FET or feed the PIC outout into a Darlington pair arrangement with a power tranny reather than a FET

[Acetronics2]

Hi, Malc ...

Think you change your Duty VERY frequently ( it's only a train ...not a jetfighter !!! ) ... so you could insert some PAUSE 100 - 300.

Secondly, you also could change DUTY ... only if the POT result changes.( a little Hysteresis w/ ADC could be useful ??? )

Third, you could insert a smooth duty transition ...

like that :


....

Dutyvar3 = 0

Main:
ADCIN 0, D

IF D <> DutyVar3 THEN

IF Dutyvar3 > D then Dtemp = Dtemp - 1 '( 1, 5, 10 ... as INERTIA needed ! )
IF Dutyvar3 < D then Dtemp = Dtemp + 1

DutyVar3 = Dtemp


ENDIF


PAUSE 200 '( to be trimmed ... 200 for 1 Channel, 100 for 2
Channels ...)

GOTO Main

... or something like that !!!

Alain

[malc-c]

In a bid to get rid of the strange noise shown on the traces in previous posts I've tried using the pulseout command.

Whilst its still not perfect as the pusle width can go down to zero, the resulting squarewave that the PIC outputs is a lot cleaner as can be seen by the attached image

I'm going to get some power transistors tomorrow and develop the output stage based on a few examples I found in an old book I used some 25 years ago and see how it performs.

Here's the code if anyone is interested.

@ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BODEN_ON

TRISIO.2 = 0   'Set GPIO.2 to output.
ANSEL.2 = 0    'Set GPIO.2 to digital		
GPIO.0 = 1      'gpio.0 set to input
VRCON = 0        ' Voltage reference disabled
OPTION_REG.7 =    0

DEFINE ADC_BITS 8	' Set number of bits in result
DEFINE ADC_CLOCK 3	' Set clock source (rc = 3)
DEFINE ADC_SAMPLEUS 50	' Set sampling time in microseconds

D var byte

main:
ADCIN 0, D 
PULSOUT GPIO.2 ,D                                  
goto main

[malc-c]

Guys, thanks for your input to this idea, however I think I'll opt for a controller using descrete parts afterall. I played about with a few transistors and the FET and managed to get some control over a loco... the drawback was that the armature sang due to the frequency of the pulses !!

Mind you I've learnt a bit more of PBP along the way, so it hasn't all been a waste of time

[Darrel Taylor]

Hi Malcolm,

Don't know anything about trains, but I can say with somewhat good confidence, that the waveforms you were getting are due to the Soundcard Oscilloscope.

Sound cards have a capacitively coupled input, And most have a minimum of around 20hz that they can see. That's a 20hz sine wave, not a squarewave. When you changed to pulsout, you can see on your picture that the frequency went up to almost 2khz, so it was able to at least see the waveform, even though still inaccurately.

I ran the program here (although on a different chip) and got a nice clean 40hz PWM.

It looks like you've given up on the PIC idea already so I won't bore you anymore.

But if you're going to build it out of transistors, this might help.
Various Transistor Throttles
http://home.cogeco.ca/~rpaisley4/Throttles.html

regards,