Handling I/O pins in a microcontroller - problem occurs

[gravi]

Handling I/O pins

Dear Friends,

In one of my application my microcontroller's I/O pin is interfaced with a digital sensor whose output is 0v or 5v. I have interfaced microcontroller I/O pin and sensor with an 10K pull-up resistor. Even then we have observed some floating voltage on I/O pin. so I have been trying to interface with an IC whose O/P is high only when the I/P is more than an threshold voltage like 2.5v or 3.0 v. If this condition fails, O/P should be LOW.

Thanking you.
Ravi Kumar

 

[ssankurathri]

Re: Handling I/O pins

hi
u can use a buffer to connect the sensor output to microcontroller's input. This buffer will increase the current capability.

other solution would be to use a inverter buffer and take care in the logic.

as u r already using a pull up resistor that should work fine.

if i understand correct, the output from sensor is either ground or 5v. right?

Regards
skr

 

[nandhu015]

Handling I/O pins

why dont you try a pull down?

Nandhu

 

[ssankurathri]

Re: Handling I/O pins

hi
as nandhu said, u can try pull down resistor.
nandhu: what can be wrong for pull up not working in this case?

 

[gravi]

Re: Handling I/O pins

Yes Output of sensor is either ground or 5v.

Yes, I can try with pull-down but my default condition is high (5 V). In worst case i will use pull-down changing my logic.

but I guess I can use buffer IC as ssankurathri suggested.

Thanking You
Ravi Kumar

 

[ssankurathri]

Re: Handling I/O pins

hi
if i were u, i will disconnect the sensor from micro first and connect the pull up resistor. try using a 1k pullup resistor.

can u please check the internal circuitary on the I/O pin in the microcontroller?

if this info. is helpful, plz click on helped me.

 

[nandhu015]

Re: Handling I/O pins

hi
as nandhu said, u can try pull down resistor.
nandhu: what can be wrong for pull up not working in this case?

The sensor is not capable of pulling down. Either use high value pullup or pull down.

Nandhu

 

[ssankurathri]

Re: Handling I/O pins

hi nandhu,
i didn't get ur comment. if the sensor can't provide the proper ground, then the pull up should work fine. right?
i mean the micro pin should see 5v all the time. why it can be floating sometimes when we use pull up resistor?

regards
skr

 

[tocal09]

Re: Handling I/O pins

He meaned that output of your sensor maybe isn't strong enought to pull the static of microcontroller's input down to ~0V. And he recommended you changed your pull down resister to higher value (example:33kΩ or 47kΩ) to make the static easier to pull down to 0V.

 

[hsacyl]

Re: Handling I/O pins

He meaned that output of your sensor maybe isn't strong enought to pull the static of microcontroller's input down to ~0V. And he recommended you changed your pull down resister to higher value (example:33kΩ or 47kΩ) to make the static easier to pull down to 0V.

I agree with you.
Should check whether the res value suitable for the MCU and sensor used.

 

[tocal09]

Sorry. I said about pull-up resistor not pull-down resistor.