Recommendations - Model Train Controller

[malc-c]

Ok I think I now understand the settings for ANSEL. Reading the datasheet again

ANSEL — ANALOG SELECT REGISTER (ADRESS: 91h) (PIC16F676 ONLY)

ANS7 ANS6 ANS5 ANS4 ANS3 ANS2 ANS1 ANS0
bit 7 bit 0
bit 7-0: ANS<7:0>: Analog Select between analog or digital function on pins AN<7:0>, respectively.
1 = Analog input. Pin is assigned as analog input.(1)
0 = Digital I/O. Pin is assigned to port or special function.

So if I wanted all analogue I set ANSEL to 11111111 - all digital 00000000

Ergo to set AN0, AN1, AN2 and AN4 Ansel should = 00010111, which is exactly what Darrel suggested. However when compiled with this setting the 4th output still runs at full speed with no control.

Could it be that the issue is with the declaration of the array - as it has [3] and I would assume that there are 4 channels so maybe this should be [4] ??

Could it be that the issue is with the declaration of the array - as it has [3] and I would assume that there are 4 channels so maybe this should be [4] ??

Looked like that was teh cause - I now have 4 working channels... just need to resolve the issue of the PIC locking on at full throttle and I'm done !

[Darrel Taylor]

Boy. Try to get some sleep, and people start talking to themselves.

Looks like the guy you were talking to, helped figure a couple things out though.

Good catch on the array size. Didn't see that.

Heard the video. That's just nasty sounding.
Is it any better yet after the changes?

I know you were told to change SPWM_RES to 255, but it really should be 256 for 8-bit resolution. Maybe the cause of the "PIC locking on at full throttle". I'll play with it here too and see.
<br>

[Darrel Taylor]

After further playing.

I can't make it "Lock".

Tried all 4 channels, tried 255/256 RES.

Incidently, 255 does work better. It's not the way I thought I wrote it. But...

That way 0 is always off, and 255 is always on.
<br>

[malc-c]

Darrel,

If using an LED its hard to make it lock. I think its either related to the power supply I'm using, or some other factor within the circuit as it does it on several loco's. I have a 0.1uf spread accros the power pins of the PIC, and power rails in a bid to decouple the supply. I've also tried changing the 1K base resistor between the NPn and PIC output as I though that the driver circuit may be drawing more than the 25ma the port can take, but that made no difference

Is the PWM outout a square wave, sawtooth or just spikes that are increased in frequency? I would like to stick with PWM as there is less heat to dissapate in the circuit and it provides far better slow starts than varible voltage type controllers. Maybe I should look at using a PIC with hardware PWM, like the 16F690 ??

[Darrel Taylor]

Definately Squarewave. This is about a third of the way on the POT.


Well, before you change pics. Can you give this program a quick try.
It's just a single channel, no interrupts. It runs at about 3.8khz

It should give an indication whether the higher frequencies of hardware PWM will help or not.

@ __CONFIG _HS_OSC & _WDT_ON & _PWRTE_ON & _MCLRE_OFF 
DEFINE OSC 20
CLEAR
ANSEL=%00110001
CMCON=7
TRISA=%11111111        'set PORTA as all input 
TRISC=%00000001        'set PORTC as all output apart from RC0

PWM1       VAR PORTC.2
DutyCycle1 VAR WORD
GoDone     VAR ADCON0.1
ADCON1 = %00110000
ADCON0 = %00000011
while GoDone : wend

Main:
  if ADRESH > 1 then
    high PWM1
    DutyCycle1 = ADRESH
    GoDone = 1
    pauseUS DutyCycle1
    low  PWM1
    pauseUS 255 - DutyCycle1
    while GoDone : wend
  else
    low  PWM1
    GoDone = 1
    while GoDone : wend
  endif    
goto Main

[mister_e]

as long as the POT impedance meet the maximum recommended.. it shouldn't be much of a problem.

What happen to your supply when you plug your loco directly?

Now, If you add 1 or more?

Now do the same but add your transistor to drive them.. what happen?

i got my few motor here, i'll do some test later.

[mister_e]

Well well well... running 3 different Motor type from 500mA to 10A @12Vdc.. and a pretty messed up breadboard + Jumper it works

2 channel PWM... all square...

3 pwm ... still the same, life is good

BUT... when you add ADCIN 4, DutyVar4... somethings goes bad....

Do one test with anything matched with ADCIN 4... something go really bad... where it comes from... i don't know for now.

Same thing happen if you do something with DutyVar4...

scratch scratch scratch

[malc-c]

Well, before you change pics. Can you give this program a quick try.
It's just a single channel, no interrupts. It runs at about 3.8khz

It should give an indication whether the higher frequencies of hardware PWM will help or not.

@ __CONFIG _HS_OSC & _WDT_ON & _PWRTE_ON & _MCLRE_OFF 
DEFINE OSC 20
CLEAR
ANSEL=%00110001
CMCON=7
TRISA=%11111111        'set PORTA as all input 
TRISC=%00000001        'set PORTC as all output apart from RC0

PWM1       VAR PORTC.2
DutyCycle1 VAR WORD
GoDone     VAR ADCON0.1
ADCON1 = %00110000
ADCON0 = %00000011
while GoDone : wend

Main:
  if ADRESH > 1 then
    high PWM1
    DutyCycle1 = ADRESH
    GoDone = 1
    pauseUS DutyCycle1
    low  PWM1
    pauseUS 255 - DutyCycle1
    while GoDone : wend
  else
    low  PWM1
    GoDone = 1
    while GoDone : wend
  endif    
goto Main

Interesting..... works fine, no drop out or locking up after 20 or so tests. However the noise from the armature when starting is very loud and high pitched, with harmonics as you increase the throttle.

I tried reming out the last two channels as Steve suggested with the original code and I still experienced problems... but this new code works.

[mister_e]

Malc,
it's little bit more than rem ADCIN line. i'll place all the changes i made in RED

@	__CONFIG  _HS_OSC & _WDT_ON & _PWRTE_ON & _MCLRE_OFF 


	ANSEL = %00010111    			; - dt suggested value



	DEFINE OSC 20
	CMCON=7
	TRISA=%11111111        			'set PORTA as all input 
	TRISC=%00000001        			'set PORTC as all output apart from RC0

	DEFINE ADC_BITS  8     			' ADCIN resolution  (Bits)
	DEFINE ADC_CLOCK 2     			' ADC clock source  (Fosc/32)
	DEFINE ADC_SAMPLEUS 11 			' ADC sampling time (uSec)

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

	DEFINE SPWM_FREQ  150                	; SPWM Frequency
	DEFINE SPWM_RES   255               	; SPWM Resolution

	DutyVar VAR byte[4]

ASM
SPWM_LIST  macro                    	        ; Define Pin's to use for SPWM
    SPWM_PIN  PORTC, 2, _DutyVar                ; and the associated DutyCycle variables
    SPWM_PIN  PORTC, 5, _DutyVar+1              ; Notice the underscore before variables
    SPWM_PIN  PORTC, 4, _DutyVar+2
    SPWM_PIN  PORTC, 3, _DutyVar+3
  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, DUTYVAR[0]
 	ADCIN 1, DUTYVAR[1]
	ADCIN 2, DUTYVAR[2]
 	ADCIN 4, DUTYVAR[3] 
 
	GOTO Main

Now for the noise, to me, as i'm not a motor pro, there's something normal in that. Your motor have a comfort zone in which he can operate. So if you're under that (let's call it threshold, lower possible voltage or else), for sure he will yell. It has to fight the inertia.. (OK OK probably not the right term... but it's how i understand )

Now, is this louder using PWM or not? this is why i asked for a variable supply before.

If it's better, we could still redesign the whole thing... same thing if you find a PWM frequency which reduce the noise.

Time for few tests on your side... even if you use few battery in serie