Im just trying to understand this image since 1 weeks.Someone please explain me.
It is not necessary to name your image with a name like that.
You and your banana completes a circuit: +5V--2meg--banana--you--GND.
Input resistance of an analog input is very high (>100meg) compared to you and the B.
Normally A0 sees +5V.
With you and B in the circuit, the voltage on A0 will be less.
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How can voltage go over me without transistor ?
Moist skin resistance can be quite low, 10,000 ohms for example.
You probably will not feel the current through your body but its flowing just the same.
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And if i dont touch banana , the voltage in a0 should be very low isnt it ?
The banana's resistance is relatively low also.
A0 will read a voltage less than 5 volts when there is current flowing through you and your banana.
Note: when your hands are dry, the voltage on A0 will be higher than when your hands are wet.
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And if voltage doesnt low its 5v then why we use resistor ? Cant we just connect it.
It sounds like you have little experience with electricity.
Here is a schematic:
What do you think is the voltage on:
A0
A1
A2
A3
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The point is to make a resistive divider using the resistor and you+banana as the two resistors.
If you just connect A0 to 5V it will read 5V whether you touch it or not.
larryd:
It sounds like you have little experience with electricity.Here is a schematic:
What do you think is the voltage on:
A0
A1
A2
A3.
Oh now i understood , we make a voltage divider.Yes , actually i have no experience with electronics i was a game programmer.
So we use a high resistance resistor because our body's resistance is high too.Is it true ?
I made a simple voltage dividor using 2.2k resistors and if i use myself and my banana for second resistor it wont work , i think thats because use a very small resistor (2.2k).
Thats my circuit.
And answers to your circut :
A0 = 0.02v
A1 = 5V
A2 = I dont know this because i dont know the "I"
A3 = 2.5V
is my answers true ?
A2 is wrong - you don't need to know the current. Even if you did need to know it you can calculate it with ohms law.
Hint an Analog input measures voltage.
Grumpy_Mike:
A2 is wrong - you don't need to know the current. Even if you did need to know it you can calculate it with ohms law.
Hint an Analog input measures voltage.
Its 5V right ?
A2 is directly connected to GND (0Volts)
Therefore A2 will see 0 volts.
No you are an expert now!
if you are not getting the voltage reading you expect, there is probably no current flowing in the divider circuit.
This might be due to the banana or your hands not being moist enough.
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larryd:
A2 is directly connected to GND (0Volts)
Therefore A2 will see 0 volts.No you are an expert now!
if you are not getting the voltage reading you expect, there is probably no current flowing in the divider circuit.
This might be due to the banana or your hands not being moist enough..
Ah i noticed now.
İm getting voltages as i expected now , i realy solved this.
Finally i just got one more question 
Why i need to use high resistance resistor like 1Mohm or 2Mohm , if i use low resistence resistor like 2.2kohm electric wont go over me cause of my high resistance.Is this logic true ? I need to read something about how resistances share electric..
If you were to use 2.2K instead of 2Meg and you and the banana were 10K then there would be ~5 times more voltage across you compared to the 2.2K.
That is ~4.1 volts on A0. (.9 volts across the 2.2K)
If you led go of the banana there would then be 5 volts on A0.
The range would be 4.1 to 5 volts. this might not be enough difference for your project to work.
When you use a 2Meg, the range is .02 to 5 volts, a much larger range for your sketch to play with.
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