MikroBasic to PBP Pro: Boost mode SMPS

[jmgelba]

I used it once for logging and removed it. I did compensate for the write period. I actually slowed it down a lot so I could see what was happening at individual increments.

I tried i = fb and incrementing the i byte and not the fb byte and it works. I get a smooth up and down output now. It will current limit at each brightness setting.

So, there is the last problem to resolve:

When ramping up I am using duty cycle to increase brightness from zero to full on regardless of where the current limit is set at. The problems are that when I save the new current limit during the main loop, I get flashing as the output goes off during the write command and the pause 10 after the write command. Therefore, I can either write to EEPROM and ramp up to the newly set current limit, or have no flashing and ramp up to full output, go to the main loop and drop straight back to the new current limit. Both options dont look very good.

I am not sure how to write to EEPROM and stop it from flashing.

[cncmachineguy]

I think you may need some logic in there to check for button release. As it looks now, it will run the fb = fb - 1 VERY fast, and every time through the loop when you press the button. Chances are you will not release the button before lots of main loop runs.

[jmgelba]

That is very true. I added a pause of 50mS in each button press if-endif routine.

The problem with that is the LED's flicker each time the button is pressed. Not sure why the pause should effect the PWM. I thought that the PWM was continuous unless you turned it off with CCP1CON = 0. That was my basic understanding anyway and the theory behind the idea. Run pwm continuously and vary the duty cycle based on a target current limit and the actual feedback results. Add or subtract by one the duty cycle number until the current limit is achieved.
Also the LED's flicker when ever there is a WRITE command so I created a counter that only writes the value every 25000 cycles.

[Ioannis]

Even with 25000 cycles EEPROM will wear out relative soon.

About the button,maybe you can try to wait for the button release before proceed.

Also the the idea of add or subtract one to the duty cycle in theory it will work, practically will have a lot of jitter. Here PID control may help (more complicate though).

Ioannis

[jmgelba]

I'd be willing to learn about PID's. It's something I wanted to do anyway. Have you worked with them Ioannis?

[Ioannis]

For something similar to what you try, but not succesfully. It just oscilated and could not fix it.

I will try again, but am busy right now.

Ioannis

[jmgelba]

After some tweaking I have this pretty much working now. I can get it to ramp up slowly to full brightness, maintain a set level, be adjusted up and down, have the new value write to EEPROM and next time it is powered up it will ramp up to the last saved level. All I want to add now is ramp down at power off. Not a problem.

I'd like to reduce code size though. I have a lot of IF THEN's and a lot of FOR NEXT's. They are used to increment and decrement a byte value based on which level output is set.

 rampup:l = 0
for l = 0 to led
if L = 0 then 
fb = 0
CCP1CON = 0
ramp = 0
portc.2 = 0
endif


IF L = 1 then
fb = 10
endif


if L = 2 then
fb = 45
endif


if L = 3 then
pause 25
fb = 90
endif


if L = 4 then
pause 40
fb = 130
endif


IF L = 5 then
pause 50
fb = 170
endif


if L = 6 then
pause 75
fb = 280
endif


if L = 7 then
pause 100
fb = 450
endif


adcin 1, temp
If temp > fb and L > 0 then
ramp = ramp - 1
IF ramp <= 0 then
CCP1CON = 0
ramp = 0
portc.2 = 0
endif
endif
If temp < fb Then
ramp = ramp + 1
If ramp >= 40 then 
ramp = 40
endif
endif
If ramp > 41 then
ramp = 0
endif


CCP1CON = 111100
PR2 = 44
high_duty=(ramp>>2)        'high 6 bits in CCPR1L
      low_duty=(ramp<<6)         'low two bits for CCP1CON
      low_duty=(low_duty>>2)           'shift back to CCP1CON<5:4>
      low_duty.3=1                     'PWM configuration bit
      low_duty.2=1                     'PWM configuration bit
CCPR1L=high_duty
CCP1CON = $0C
T2CON = 4


pause 100
next l
goto main

This is the ramp up routine that seems to work well. The ramp down is similar. Any way to reduce this block of code in size?