External Interrupt in AVR

[movie_freak]

avr external interrupt

Hi,

I am doing this

DDRE &= ~(1<<4);
                SREG &= ~(1<<7);
		/* Initialize external interrupt on PE4 */ 
		EIMSK  |= (1<<INT4);
   		EICRB |= (1<<ISC40);    // For any logical change the interrupt triggers
		SREG |= (1<<7);

catching it with:

ISR(INT4_vect)
 {
       // Here i do anything
 }

In the hardware i am having the sensing connected to the controller through a resistor.

Its an ATmega. The input being sensed is 12V(high) DC or 0V(low) DC


The issue: This pin is so vunerable that even if we touch it with hand, or a tweser it executes the "INT4_vect interrupt.

So how can i stabilize this?


Many Thanks,
Surya

 

[nandhu015]

avr external interrupts

use low pass filer and a schmitt trigger

Nandhu

 

[movie_freak]

external interrupts avr

Thanks Nandhu,

I made a scmitt trigger with lm324, but it didnot solve my problem? I did not use a low pass filter though.

Actually, im not good in this.. , so i wanna ask you if i need to add the low pass filter after the scmitt trigger or before it?

The problem is still the same: the external interrupt executes even if we touch the pin or connecting wire, it's so vulnerable that if we connect a wire and leave it open and move our hand near the wire the interrupt executes.. :?: ..(the output of scmitt trigger is now 2.9 V or 0V but still the issue persists ) and i want it to stabilize?


Many Thanks,
Surya

 

[nandhu015]

external interrupt avr

Hai

Can u post the schematic

there must be a problem with your hardware i think,

If possible please post the hole code, This will help me to point out the exact problem easily

Regards
Nandhu

 

[movie_freak]

external interrupt with avr

This is the circuit i have made[/img]

 

[imam.sumarsono]

interrupt in avr

Above schematic is comparator with hysteresis, I think u must use OP-Amp that specifically used as comparator like LM393.
But you must first try to use RL at the input of Micro controller to ground (ex. 1 K).
But, I have see abnormal at your schematic, your MC using 5 V DC, but your comparator using 12V DC, I think it is influence to the system.

regards,
-Imam-

 

[movie_freak]

avr input 12v

But you must first try to use RL at the input of Micro controller to ground (ex. 1 K).

I just forgot to show in the diagram there is a 10k between the input of controller and ground


I hope lm324 may also serve as the op-amp required for this application, and hysteresis is added in the process of resolving the issue to remove the vulnerability

But, I have see abnormal at your schematic, your MC using 5 V DC, but your comparator using 12V DC, I think it is influence to the system.

I also did not get what's abnormal in using the controller on 5V DC and the comparator to compare a 12V signal?? Can you elucidate it?


Thanks,
Surya

 

[imam.sumarsono]

avr interupt pull up

But you must first try to use RL at the input of Micro controller to ground (ex. 1 K).

I just forgot to show in the diagram there is a 10k between the input of controller and ground


I hope lm324 may also serve as the op-amp required for this application, and hysteresis is added in the process of resolving the issue to remove the vulnerability

But, I have see abnormal at your schematic, your MC using 5 V DC, but your comparator using 12V DC, I think it is influence to the system.

I also did not get what's abnormal in using the controller on 5V DC and the comparator to compare a 12V signal?? Can you elucidate it?


Thanks,
Surya

if u use LM324, when this op-am (as comparator) output as high, it will generate +VCC in output, so if you use 12 VDC in your comparator, when it generate high output it will give + 12V to Microcontroller input, I think it will damage microcontroller logic. If u use LM 339 it use open collector output when high state. So, I think it will better, and u can use Resisstor pull up 5 V.
Have you try to another schematic?, I think you must try this schematic (at attachment)

regards,
-Imam-