Surviving 1 second without battery power

[peu]

Rest helped clear my mind

I will test this code as soon I arrive at my office:

@ device pic12f683,INTRC_OSC_NOCLKOUT , wdt_on, mclr_off, protect_off, bod_on

CMCON0 = %00000111     ' Disable comparator
VRCON  = %00000000     ' disable


'       I/Os
TRISIO = %00000000      ' no inputs      

' definitions
 
' init values

if PCON.0=0 then
  gpio=%00000100            'Brown-out detected turn on LED on PIN5
else
  gpio=%00000010            'Brown-out NOT detected turn on LED on PIN6
endif

'main loop

loop:
goto loop

I can't imagine simpler code to test the BOD function. Do you see something wrong?

[Acetronics2]

Hi,

Was not so easy ... but finally got it !!!

all the trick is in the bits setting and testing scheduling ... Always keep in mind the processor will re-start from the beginning.

Have fun ... the ( let's be modest ! ... A ) working listing waits for your first try ...

Other trick : May be you'll have to test greater values capacitors ...

Alain

[skimask]

Hi,
Was not so easy ... but finally got it !!!
all the trick is in the bits setting and testing scheduling ... Always keep in mind the processor will re-start from the beginning.
Have fun ... the ( let's be modest ! ... A ) working listing waits for your first try ...
Other trick : May be you'll have to test greater values capacitors ...
Alain

You know...I was thinking...
In this type of project, there's nothing that says the PIC has to turn itself completely off right away.
Why can't it stay running for, say 10 seconds, after the LED is powered off.
So, the process looks like this:

Initial power on with an initial mode...
LED lit, PIC waiting...
button pressed, LED off, PIC still waiting...
If one second passes without a button press, the PIC shuts itself off.
If a button press happen inside of one second, the mode changes and the 1 second timer is reset.
Requires a bit more thought with the single button power on/off circuit, but that's easy...

[Acetronics2]

Hi, Ski

My tries show the processor runs in a Low Power mode ...

Your solution is easy with the ADC (or a comparator ! ) instead of the BOR ... But the goal was NOT TO USE an adc.

I know ... a '675 doesn't cost so much more than a '629.


Just consider it was another forum " for the fun contest" !!!

Alain

[falingtrea]

One thing to remember. The diode D1 is isolating the PIC supply from the LED. So the PIC should be able to stay in a brown out mode for a small amount of time. But your test circuit may have a problem if the indicator LED is directly connected to a PIC I/O pin. The LED may then drain the PIC power too fast and the PIC will go into POR quicker. The AMC7135 parts in the original design isolate the PIC pin enough so that it can still run off the cap charge. You need a higher impedance connection, on your test board, to the PIC to keep this from happening. Maybe you can put a buffer (like a HC04) between the indicator LED and the PIC pin and power the buffer straight off the supply.

Also in your code, when you check the BOD, you also need to check the POR. This is because you will have one of two situations:

BOD cleared but POR still set - Switch click
BOD cleared and POR cleared - powered down

Your code also needs to set both bits after they are checked, otherwise they will never be '1'. The hardware only clears the bits when a situation happens. It is the program's responsibility to set these bits.

[peu]

You know...I was thinking...
In this type of project, there's nothing that says the PIC has to turn itself completely off right away.
Why can't it stay running for, say 10 seconds, after the LED is powered off.
So, the process looks like this:

Initial power on with an initial mode...
LED lit, PIC waiting...
button pressed, LED off, PIC still waiting...
If one second passes without a button press, the PIC shuts itself off.
If a button press happen inside of one second, the mode changes and the 1 second timer is reset.
Requires a bit more thought with the single button power on/off circuit, but that's easy...

This is the circuit Im using:


With this code:

@ device pic12f683,INTRC_OSC_NOCLKOUT , wdt_on, mclr_off, protect_off, bod_on

CMCON0 = %00000111     ' Disable comparator
VRCON  = %00000000     ' disable


'       I/Os
TRISIO = %00000000      ' no inputs      

' definitions
 
' init values

if PCON.0=0 then
  gpio=%00000100        'Brown-out detected turn on LED on PIN5 (red)
else
  gpio=%00000010        'Brown-out NOT detected turn on LED on PIN6 (green)
endif

'main loop

loop:
pcon.0=1
goto loop

It does not work, the minute I give it power green lits and after 5 seconds¿?¿? it goes off and red lits.

Am I missing something?

I can use a 12F675 or even a 12F683 if a simpler / more efficient solution is possible.

Regarding flashlight operation, think of a flashlight without buttons, it goes on or off by twisting the body, and the battery electrical path to the LED/uC is done using the metal body. So this means when power is gone, is gone for everything. To be even more clear, here is a CAD drawing of my latest creation:


The green you see there is the uC/driver PCB that also serves as positive contact for the battery. Ground is attached inside the flashlight head.

To check more flashlights check: www.neoca.com.ar Thanks!

[Acetronics2]

Hi, Peu

You're out ...

'@ device pic12f683,INTRC_OSC_NOCLKOUT , wdt_on, mclr_off, protect_off, bod_on

 @    __config _INTRC_OSC_NOCLKOUT & _PWRTE_ON & _WDT_ON &_BOD_ON & _MCLRE_OFF & _CP_OFF
 
 
OSCCON = %01100110
CMCON0 = %00000111     ' Disable comparator
VRCON  = %00000000     ' disable
ADCON0 = %11100000
ANSEL  = %10000000

'       I/Os
gpio   = %00000000
TRISIO = %00000000      ' no inputs 

BOD var GPIO.0
POR var GPIO.1

   
IF PCON.1 = 0 and PCON.0 = 0 THEN BOD = 1	'BROWN OUT RESET BIT
IF PCON.1 = 0 				 THEN POR = 1	'POWER ON RESET BIT

PAUSE 1000

GPIO = 0

if PCON.1 = 1 AND PCON.0 = 0 then		'PCON.0 = BOD ;PCON.1 = POR
          
    GPIO.2 = 1         'GPIO.1 red led PIN6 shows a BOD state
    PAUSE 5000
    PCON.0 = 1
    gpio = %00000000
    
endif

PCON.1 = 1
PCON.0 = 1

While 1
Wend

END

This works really fine, but with a 10 µ (MICRO) F ...and a 12F683

so , some current draw improvements are still to add ...

NOTE: All Outputs are Mosfet Buffered ( BS 170 ) ...

Alain

PS: You didn't use your brain too much, here ....

[falingtrea]

Change your test circuit as follows:

Put a diode between the cap and the battery disconnect point like the sample schematic at the beginning of this thread has. This will isolate the PIC power from the rest of the circuit so that the cap will power the PIC when the battery is disconnected.

Connect the LED cathodes to the I/O pins. Then connect the LED anodes to the battery disconnect point between the battery and the diode that was added above. By doing this, the LEDs won't draw power once the battery is disconnected.

[peu]

[edit] Maybe I need to check for POR=1 and BOD=0 to know for sure that a BOD reset happened

I wasn't that far with this late edit

This works really fine, but with a 10 µ (MICRO) F ...and a 12F683

so , some current draw improvements are still to add ...

NOTE: All Outputs are Mosfet Buffered ( BS 170 ) ...

Alain

PS: You didn't use your brain too much, here ....

What brain?

Well I implemented your program and it worked, but the cap value was way too high, so I started lowering till I found a ridiculously low value...

Then I examined your code, removed some chunks and commented it:

@ device pic12f683,INTRC_OSC_NOCLKOUT , wdt_on, mclr_off, protect_off, bod_on

' I use picbasic to compile!!

 '@    __config _INTRC_OSC_NOCLKOUT & _PWRTE_ON & _WDT_ON &_BOD_ON & _MCLRE_OFF & _CP_OFF
 
 
OSCCON = %01100110
CMCON0 = %00000111     ' Disable comparator
VRCON  = %00000000     ' disable
ADCON0 = %11100000
ANSEL  = %10000000

'       I/Os
gpio   = %00000000
TRISIO = %00000000      ' no inputs 

' SECTION? what is this section used for?
' BOD var GPIO.0
' POR var GPIO.1

   
' IF PCON.1 = 0 and PCON.0 = 0 THEN BOD = 1	'BROWN OUT RESET BIT
' IF PCON.1 = 0 THEN POR = 1	'POWER ON RESET BIT

' PAUSE 1000  this pause cannot be used in a flashlight environment
'  SECTION?  what is this section used for?

GPIO = 0

if PCON.1 = 1 AND PCON.0 = 0 then		'PCON.0 = BOD ;PCON.1 = POR
          
    GPIO.2 = 1          'GPIO.2 green led PIN6 shows a BOD state
    PAUSE 1000          'I don't have patience :-)
    'PCON.0 = 1         ' not needed since you set this again below
    gpio = %00000000
    
endif

'PCON.1 = 1      replaced with one line :-)
'PCON.0 = 1
PCON=%00000011

GPIO.1 = 1 'normal state red led
While 1
Wend

END

and if a picture is a 1000 words, we could say that a video is like 1000 pictures, so 1000x1000=1000000 words... WOW... I just wrote a book take a look at this video: http://www.veoh.com/videos/v6415763hQHpjMDy

As you see, the cap is reaaally small, the green led shows BOD condition, and red led is normal operation. The diode you see there is not used. Also I left all the unused pins floating

When I used large value capacitors, everytime I did a power interruption no matter if it was 1 second or 10 the BOD led turned on.

I wonder why you had to use 10uF

Also assembled a proto PCB using the 1st schematic to start testing a real world application.

[Acetronics2]

I wasn't that far with this late edit

What brain?


.

" Whose brain ??? " could have been good level humour ...

Well I implemented your program and it worked, but the cap value was way too high, so I started lowering till I found a ridiculously low value...

Then I examined your code, removed some chunks and commented it:


<< ' I use picbasic to compile!! >>

Me too !!! ... did you notice a little difference between MPLAB and Microcode studio ???


<< I wonder why you had to use 10uF >>

I don't know ... gives me a ~ .3 s power interrupt delay ... and it won't be my headache !!!
The Pic itself draws .77 mA ...

Regards
Alain