Hy
I'm working on a Project with 7 Arduino's conected like this with a 20W 5V power Supply.
The cables are 2m long...
The last Arduino does just get 3.6V....
How can I make the voltage more stable?
I'm not the guru in Electronics but I hope you can help me 
Thx
Andy
Which Arduino boards are you using? Duemilanove?
Duemilanove
Where is the power coming OUT of the Arduino that goes to the next one?
A1 is the arduino in a box
Must you wire these as a daisy-chain (vs a separate wire from the power supply to each Arduino)?
Yes I have to chain it like this...
Are you powering other things from each Arduino board? What? How?
It's an Arduino, 3LED, and an Xbee togehter they consum 80mA
So - are you daisy chaining, or using a bus topology? Your second picture seems to indicate a bus, while the first seems to indicate a daisy chain...?
What gauge and style (stranded or solid) type of wire is being used for the power run?
You might end up having to push more voltage (12-24 volts), and regulate it down at each board; we need more details (exact schematics of the power distribution network would be nice)...
It's daisy chaining for sure... The arduinos are placed on a table...
The power Wire hhas .75mm^2 and is a normal one.
The Xbee is connected through a Sparkfun Xbee regulator. And the led through a resistor.
Power wire from the Box does directly go to the 5v Pin from the Arduino
Hmm 12v why not... I just have to solder the wire ti the VIN of the Arduino and not the 5v...
Is the ground wire also wired in the same manner as the +5vdc wire?
Lefty
yes
Well take a meter, DVM, and measure the +5vdc and ground value at each board and write if down. After you measure them all see if the voltage drop is the same as you move down each board. If it seems like a consistant voltage drop from board to board then you just need 'fatter' wire for the +5vdc and ground daisy chains and/or better connection method for each 'board tap drop'.
Lefty
Well take a meter, DVM, and measure the +5vdc and ground value at each board and write if down. After you measure them all see if the voltage drop is the same as you move down each board. If it seems like a consistant voltage drop from board to board then you just need 'fatter' wire for the +5vdc and ground daisy chains and/or better connection method for each 'board tap drop'.
Lefty
I will check this tomorrow. I just plugged 12v and 9v in and both worked great.
With 12v the Arduino got quite hot so 9v would be better but I try to connect all with 5v.
HOW are you connecting these four .75mm wires to each box? Are you using some kind of connector? Is there a separate connector for input and output (to the next box)?
yes there are two connectors on each box:
one for the input one for the output. but the input and output connector are both wired together.
Are they too smal??
One box uses:
conected to 5v, GND, RX, TX
and some square LED's sorry don't got any link...
sorry my English isn't that good so I liked to say that 12v and 9v worked great and I connected those to the VIN pin!
But i try to stick with the 5v Power supply which will be connected directly to the 5v pin...
sorry my English isn't that good so I liked to say that 12v and 9v worked great and I connected those to the VIN pin!
But i try to stick with the 5v Power supply which will be connected directly to the 5v pin...
Your english fine and I read earlier that you were using the Vin pin with the 12v attempt. Given the choise of daisy chaining +5vdc or +9-12vdc, I would certainly recommend the latter for several reasons.
Lefty
thx for all your advices. I will now stick with a 9V source and I will use the regulator from the Arduino.
Does work great even with 7 Arduinos attached.
andy