RE: [PIC] High Power Consumption for a Battery operated application - Electronic Safe

Francois -

Getting a PIC microcontroller to minimum standby current can be complicated.
Do you have the whole schematic? Try these steps:

1) Make sure that EVERY pin is at HIGH or LOW level when the device is in
standby mode. Any CMOS pin in a mid-level mode will eat power.
2) Make sure the pins that are driving external things are in a low power
situation. By that I mean that no pulled-up pins are pulled-down during
standby, and vice versa.
3) Make sure the clock oscillator has stopped in standby mode.

I make a lot of PIC-based battery operated products and my final check is
always to put the device is low power standby mode and then probe every pin
in turn with the 'scope to make sure they are all in the mode for zero power
use.

Chris Fox

************************
Christopher W. Fox
Consultant/Engineer/Programmer
(210) 823-5671  eMail: [email protected]
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attachments.

-----Original Message-----
From: Piclist <[email protected]> On Behalf Of Francois Robbertze
Sent: Tuesday, January 7, 2025 1:15 PM
To: [email protected]
Subject: [PIC] High Power Consumption for a Battery operated application -
Electronic Safe

Hi,

 

I need help with the power consumption on a battery operated project (Keypad
safe)

I have a lot of safes and the controllers is damaged. I want to create new
controllers for these safes and try to use what is available

 

Details: Current Power is supplied by 4xAA Batteries. Power is dropped to
4.8 volt through 2 diodes.

 

I used PICBASIC Pro and the software works perfect except the current draw
is about 1.56mA. The datasheet show on page 167 a current draw of 1uA in
sleep mode. I use the PIC16F88. That is with the programmer disconnected.( I
measure about 156,8mV volt drop over a 100Ohm resistor )

 

What am I missing or doing wrong? 

 

The Software in short:

 

Config:

    __config _CONFIG1, _INTRC_CLKOUT & _WDT_OFF & _LVP_OFF & _CP_OFF &
_BOREN_OFF & _MCLRE_ON & _DEBUG_OFF 

    __config _CONFIG2, _FCMEN_OFF & _IESO_OFF

 

Pin Setup: 

Row1 VAR PORTA.0                         '4x3 Keypad 

Row2 VAR PORTA.1

Row3 VAR PORTA.2

Row4 VAR PORTA.3

 

Col1 VAR PORTB.0

Col2 VAR PORTB.4

Col3 VAR PORTB.5

 

' Other pins

    Solenoid VAR PORTA.4         ' Solenoid control pin

    Beeper VAR PORTB.3           ' Beeper control pin

    ResetButton VAR PORTB.6      ' Reset button

    Led var PORTB.2              ' heartbeat

 

Initialize:

    OSCCON = %01101110               'set int rc osc to 4mhz

 

      CMCON = 7              ' Disable comparators, PORTA as digital I/O

      ANSEL = 0              ' Set all pins as digital I/O

      ADCON0 = 0             ' a to d off

      ADCON1 = 0              '??

      T1CON = 0

      T2CON = 0              ' timer 2 off

      CCP1CON = 0            ' capture compare off

      TXSTA = %00000000      '??

      RCSTA = %00000000      '??

      

      PORTA = 0              ' Initialize PORTA to 0

      PORTB = 0              ' Initialize PORTB to 0

      

      TRISA = %00000000       ' Set PORTA direction (input/output as needed)

                              ' RA0 - RA3 keypad row - outputs

                              ' RA4 - stryker - output

                              ' RA5 - reset mclr - set as input

                              ' RA6 - RA7 osc

      TRISB = %01110001       ' Set PORTB direction

                              ' RB0 - col1

                              ' RB1 - nc   

                              ' RB2 - LED   

                              ' RB3 - Buzzer

                              ' RB4 - Col2

                              ' RB5 - Col3

                              ' RB6 - nc Programmer

                              ' RB7 - nc Programmer 

                                  

      

      OPTION_REG.7 = 0           ' Enable weak pull-ups on PORTB

      OPTION_REG.6 = 0           ' TRIGGER INT ON FALLING EDGE

 

I then enable interrupt :

INTCON = %10011000                            ' enable change on port[B4-B7]
and ext int on port b

                                                            

ON INTERRUPT GOTO Handleinterrupt             ' Interrupt Service Routine

 

Main Routine:

 

Check for KeypressedFlag

Check for ResetPressedFlag

 

Flash LED 

 

Goto Sleep:

 

OSCCON = %00000010    '32KHz

            

            asm

            sleep

            endasm

 

             OSCCON = %01101110    '4MHz

 

.and goto Main

 

Here is my Interrupt Handler.

Disable

HandleInterrupt:

    if resetbutton = 1 then

        ResetPressedFlag = 1

        resume

    endif    

      

    IF INTCON.1 = 1 THEN        ' Check external INT (RB0)

        KeyPressedFlag = 1      ' Set flag for RB0

        INTCON.1 = 0            ' Clear external INT flag

    ENDIF

    

    IF INTCON.0 = 1 THEN        ' Check IOC interrupt

        'IF (PORTB & %00110000) <> %00110000 THEN

            KeyPressedFlag = 1  ' Set flag if RB4 or RB5 changes

        'ENDIF

        INTCON.0 = 0            ' Clear IOC flag

    ENDIF

    

    RESUME

    enable

 

I am currently using the PIC16F88. I tried to drop the voltage below 4Volt
with disastrous effects.

 

Should I get another PIC? . I don't want to replace the batteries every
month.

 

Regards

 

Francois

 

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