AT89s51 taking input problem

[mohammad_talha]

Ok..this might sound silly but i have a serious problem..i am trying to connect a simple switch to AT89s51 and once connected the switch ..the switch works perfectly fine ..but if i TOUCH the pin to which the switch is connected OR touch a piece of wire to ..say P2.0...it is actuated...i.e a low is detected in the programming...how can i avoid it..i.e the touch should not give a low unless it is actually grounded..

 

[plusminus]

This should work:

Now your line is low ohmic and so less sensitive to noise. Eventually you can also connect a small capacitor (10n -- 100n ) over the switch.

 

[mohammad_talha]

i am using a 10k resistor instead of 4k7in the same configuration..still doesnt work

 

[plusminus]

Try lowering the resistor. 1K or 470?. (1/4watt resistors)
The lower the resistor is the less sensitive it is to noise.
Touching directly a pin is much more sensitve then thouching the wire.
Also try the capacitor as mentioned before.

 

[syrax]

i think you know to set the pin to 1 , then try to reading
you can simple wire the button on P3.2 or P3.3 /int0; int1/ and make a simple interrupt with led