book "getting started with arduino" wrong schematic inside ?

Other Hardware Sensors
1

The book getting started with arduino contains on page 65 a drawing on how to connect an arduino for serial input
I am not deeply into electronics but to me this drawing seams wrong, the reason i conclude that is, the Arduino has 4 anolog inputs
the way it is connected here would not allow to add more analog inputs see :

So what i am thinking is was the wiring sketch to the LDR crossed perhaps ?.
If i want to use 2 LDR's should i then use :

5v --LDR (2)-----------analog 1
|
--5v --LDR (1)-----------analog 0
|
5v - resistor 1Kohm---- ground

i'm not entirely sure i or why there should be a 1K ohm between 5v and ground, maybe its for protection, i dont know why the book uses one
well maybe someone can enlight me on this on how to connect multiple analog sensors in a schematic

2

The LDR and resistor act as a voltage divider. Each LDR needs a separate resistor:

5v --LDR (2)-----------analog 1----- resistor 1Kohm---- ground
|
5v --LDR (1)-----------analog 0------- resistor 1Kohm---- ground

3

but wouldnt that be like this ?

5v --ldr 2 ---analog 1 --|
--| |---1K ohm -- ground
5v --ldr 1 ---analog 0 --|

so you get strange combinations of 3 resistors and have bot ldrs connected
i like to get readings of 2 sensors to measure

or maybe i dont get the idea of voltage devider..?

4

PGTBOOS:
but wouldnt that be like this ?

5v --ldr 2 ---analog 1 --|
--| |---1K ohm -- ground
5v --ldr 1 ---analog 0 --|

If you study your diagram you will see that analog 0 and analog 1 are shorted together. This means that they will aways have the same reading. Clearly not what you want.

The voltage drop across a resistor depends on the current flow. The current flow will depend on the total resistance in the circuit. If two equal resistors are in series between +5 and Ground the voltage at the point between them will be 2.5V. If the resistor to +5V has a lower value the point will be above 2.5V. If the resistor to +5V has a higher value the point will be below 2.5V.

5

yes but there is one ground also... so through ground it all gets connected

?

i tried this today

but hat didnt work either, for to me unknown reason the analog readout of 2 and 3 kept in a swing up and down, i wanted an independent readout