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Topic: Corruption when resistor connected to inputs (Read 452 times) previous topic - next topic

dp28688

I seem to get corruption on my display soon as i connect resistor to inputs A1-A5.  im using 10k resistor planning on float switches to them but i cant even put a resistor in the input other end in the air with out display showing random numbers.
My setup is i2c LCD, I2c RTC, temp probe 1 wire dallas. i2c expansion module pcf8574. also Atlas PH stamp .  they all seems to work fine no conflicts. just cant use my inputs. is it possible my inputs are bad on the board? this is 1st thing ive had hooked up to them so shouldnt be damaged by me.


fungus


I seem to get corruption on my display soon as i connect resistor to inputs A1-A5.  im using 10k resistor planning on float switches to them but i cant even put a resistor in the input other end in the air with out display showing random numbers.
My setup is i2c LCD, I2c RTC, temp probe 1 wire dallas. i2c expansion module pcf8574. also Atlas PH stamp .  they all seems to work fine no conflicts. just cant use my inputs. is it possible my inputs are bad on the board? this is 1st thing ive had hooked up to them so shouldnt be damaged by me.


Aren't A4 and A5 used for the i2c bus?
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dp28688

#2
Nov 19, 2012, 04:01 pm Last Edit: Nov 19, 2012, 04:05 pm by dp28688 Reason: 1
i didnt specify but im using a2 and a3 only. i may switch it over to digital side see if it works over there.

Also i have rev 3 of Arduino uno. if that info helps any.


MarkT

Quote
i cant even put a resistor in the input other end in the air with out display showing random numbers.


Indeed - that is what one should expect of a floating input, it will pick up the nearby signals because its extremely high impedance
(in fact approximately infinite impedance at lower frequencies).  Your resistor is acting as a capacitive probe to nearby wiring.

Connect the other end of the resistors to something sensible and the inputs will no longer float.
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dp28688


Quote
i cant even put a resistor in the input other end in the air with out display showing random numbers.


Indeed - that is what one should expect of a floating input, it will pick up the nearby signals because its extremely high impedance
(in fact approximately infinite impedance at lower frequencies).  Your resistor is acting as a capacitive probe to nearby wiring.

Connect the other end of the resistors to something sensible and the inputs will no longer float.


Ok i will try to connect the switch circuit.
I had it  Arduino A2->resistor->breadboard attached when i noticed issue then tried just resistor in air. i shoudl probably go ahead put resistor on breadboard then keep it away from arduino then.




MarkT

If you're not using an input, no need to look at it!
[ I won't respond to messages, use the forum please ]

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