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information for connect RS232 by PIC16F877A

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swtboy

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can anyone tell me why when i connect to PC Serial Port pin2 the voltage lose???
from 4.2V to 0.3V???
 

swtboy

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sorry about that.
i follow this circuit but i using 4 4.7uF connect with max232.
max232 tx output is 4.2V, but when i connect to PC serial pin 2 voltage become 0.3V only.
and PC serial pin 3 voltage actually is how much??
i using multimeter measure is -10V when connect with my max232 become -9V is it correct??
 

jjeevan007

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i think your multimeter battery is not working properly change it and check the voltage again.......
 

swtboy

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the multimeter can function...
i try 3 PC same voltage also...
 

jjeevan007

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if the multimeter battery gone weak then it shows higher voltage, so batter you change the battery of the multimeter and see...
 

swtboy

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i use 2 multimeter to measure same value also too...
could the problem is about the capacitor value??
coz i using 4.7uF.
if i change to 10uF will get different result?
 

swtboy

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yup...
because i saw 1 micro controller book circuit is 4.7uF
 

swtboy

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i connect with 10uF gt leaking voltage from max232

- - - Updated - - -

#define switch PORTB.F1
#define pressed 0

int i;
void main()
{
TRISA = 0xF7;
TRISB = 0xFF;
UART1_Init(9600);
Delay_ms(100);
UART1_Data_Ready();

while(1)
{
if(switch==pressed)
{

PORTA = 0xF7;
Delay_ms(100);


}
else
{
for(i=0;i<30;i++)

{
PORTA = 0xF7;
Delay_ms(100);
PORTA = 0xFF;
Delay_ms(100);
UART1_Write_Text(" ALERT!!!! ");
UART1_Write(10);
UART1_Write(13);
Delay_ms(10);
UART1_Write_Text(" HOUSE 1 ");
UART1_Write(10);
UART1_Write(13);
Delay_ms(10);
UART1_Write_Text(" THIEF BREAK IN!!!! ");
UART1_Write(10);
UART1_Write(13);
Delay_ms(100);

}
}
}
}

this is my code.
 

tony_lth

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Sometimes when I make a mistake of the polarity of the Tan capacitor, the volatge drops.
 

swtboy

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i see display some computer language...
and my code set as (alert, house1, thief break in)
but cant display...
last time i using pic board connect can function...

- - - Updated - - -

i see display some computer language...
and my code set as (alert, house1, thief break in)
but cant display...
last time i using pic board connect can function...
 

jjeevan007

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check the max232 ic that u are using that may be gone i think..........
 

swtboy

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what you means max232 gone???
 

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