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Topic: How to eliminate noise of the LM35 connected to Analog pin of Arduino..? (Read 5 times) previous topic - next topic

jackrae

And what's the crystal for that appears on the left of the circuit.   Your LCD display will use multiplexing to encode the characters which itself will generate lots of noise.  You therefore need to ensure its supply is decoupled as close as possible to the display power connects.

I know it's difficult to keep wires separated but all those wires crossing over each other will also cross-couple any noise signals to where they aren't wanted - particularly the one from the crystal (if it's an active part of your circuit)

Joy


And what's the crystal for that appears on the left of the circuit.   Your LCD display will use multiplexing to encode the characters which itself will generate lots of noise.  You therefore need to ensure its supply is decoupled as close as possible to the display power connects.

I know it's difficult to keep wires separated but all those wires crossing over each other will also cross-couple any noise signals to where they aren't wanted - particularly the one from the crystal (if it's an active part of your circuit)


Reading your post I removed both the Xtal wires and freshly connected a xtal below the board( soldered the xtal directly on the pins 9 and 10 )..

Still the problem persists..

So I removed the LCD and still found the problem persists... :(

Joy

I found that the power supply is causing the problem...
As I am using a LM7805 to power the circuirt I tried a 12 volt battery but still the noise existed..
Then I powered the circuit with the LM7805 and with a %v power supply from another arduino board(original)
There was no noise at all... :)

So what may the problem be...???
I tried 3000uf filter caps before the LM7805 and a 0.1uf non polar capon the 5volt... still the problem was there...

jackrae

Time for an accurate circuit diagram of the components you actually have wired into the system.  Sounds like you've missed out the required capacitors on the voltage regulators.  See vendor data sheets for subject regulators, where the manufacturers specify what capacitance is required at regulator input and output to prevent oscillation.

Joy


Time for an accurate circuit diagram of the components you actually have wired into the system.  Sounds like you've missed out the required capacitors on the voltage regulators.  See vendor data sheets for subject regulators, where the manufacturers specify what capacitance is required at regulator input and output to prevent oscillation.


:P how funny when I am using the small 7805 (TO- 92) there is no noise, this small 7805 does not even require a cap on its output..

But whenever I am trying to use big one there  is a lot of noise.. :(. and on its output without a filter cap it will not even boot the atmega...:P



This is the circuit of ripple rejection as on the datasheet... :(
huh its too big... :(

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