Pages: [1]   Go Down
Author Topic: book "getting started with arduino" wrong schematic inside ?  (Read 633 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Full Member
***
Karma: 2
Posts: 219
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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
Logged

Massachusetts, USA
Offline Offline
Tesla Member
***
Karma: 212
Posts: 8940
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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

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

Send Bitcoin tips to: 1L3CTDoTgrXNA5WyF77uWqt4gUdye9mezN
Send Litecoin tips to : LVtpaq6JgJAZwvnVq3ftVeHafWkcpmuR1e

Offline Offline
Full Member
***
Karma: 2
Posts: 219
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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..?
« Last Edit: June 23, 2012, 04:20:02 pm by PGTBOOS » Logged

Massachusetts, USA
Offline Offline
Tesla Member
***
Karma: 212
Posts: 8940
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged

Send Bitcoin tips to: 1L3CTDoTgrXNA5WyF77uWqt4gUdye9mezN
Send Litecoin tips to : LVtpaq6JgJAZwvnVq3ftVeHafWkcpmuR1e

Offline Offline
Full Member
***
Karma: 2
Posts: 219
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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
« Last Edit: June 24, 2012, 04:08:56 pm by PGTBOOS » Logged

Pages: [1]   Go Up
Jump to: