I finally chosen the Sabertooth2x25 motors driver http://www.dimensionengineering.com/products/sabertooth2x25
for these options:
25A continuous, 50A peak per channel
6-30V nominal, 33.6V absolute maximum
Input modes: Analog, R/C, simplified serial, packetized serial

Also has an Arduino library for packetized serial and Simplified Serial input modes. http://www.dimensionengineering.com/info/arduino

Hi,
Everything going well about this project. I have one question... For test purpose, is there a problem running my 24 Volts DC 450 watts motors with only one 12 Volts battery ?

[Design Specifications]

Found this Home Built Dual 50A H-Bridge Circuit http://www.ianjohnston.com/content/index.php?option=com_content&view=article&id=63 wich is quite nice.

- Dual Channel (able to control each output independently).
- ~50A continous per channel @ 24vdc.
- Beefy design in terms of terminals, cooling etc.
- Output stage containing both N-type & P-type Mosfet for push/pull operation.
- PWM controlled with added logic for motor direction control input.
- Logic for protection against turning both left or right side push & pull mosfets on at the same time (a sure recipe for smoke!).

Design Specifications:
DC supply / Motor drive output = 10 - 30vdc.
PWM / Direction control logic = 5vdc TTL.
PWM frequency = Tested at 488Hz (standard Arduino PWM) & 1.95kHz (should also work a lot higher).
Main output max. load (Amps) = T.B.A. (theoretically = 50A).
+5vdc supply (onboard logic & external)= 0.5 Amp max (1.0A if you upgrade the inductor).

IMPORTANT NOTE: This design offers no real over-current or over-temperature protection. You will also need a suitable heatsink.

Interesting stuff but it need to be Arduino controlled motor drivers.

The below might be worth looking at.

http://www.monsterscooterparts.com/otco.html

For my amps requirement, i could use 2 VNH5019A to get 24 A (60 A peak) to a single motor connected to both channels but i still have the 24 volts overvoltage protection issue.

Documentation also says that it can survive input voltages up to 41 V.

The VNH5019A-E itself cost $9.20 qty 1, from Digikey
Looks good. Heat sink will be needed
I'll buy one full board from polulu for testing.

No, i do not have lots of knowledge and experience but i'm ok with programming Arduino. I have to get 50+ units, would it be smart to go DIY and be guided ?

I did search about it already and do i really need this stuff ?
http://www.robotshop.com/world/pololu-dual-motor-driver-shield-arduino-3.html
Pretty much expensive, any alternative ?

Thanks

I just got back from summer hollidays, sorry for not giving back any infos soon after Nick sent his message about a fix. I did not had time to tried.
Really, only DHCP does that ? i tried both fixed IP and DHCP and the result was the same. IIRC last month test.

I found that the issue only exists when attempting to use DHCP.

Well i did change the lines inside w5100.h but it still doing the same.
Feels like i don't know what i'm doing. :-)

Nothing else we can do ? 

All sketch from the Ethernet examples. Basic stuff.
Arduino 1.0, 1.0.1 on either Windows7 or Mac OS X latest

I'm very confused at this point, i  manage to find solution all by myself most of the time, must be a silly thing hanging there.

Actually, i was referring to D4, D5, D6, D7 

Anyone here has Ethernet working on Mighty 1284p ?

Nick,
Pretty much straightforward set-up. It works with any atmega i have here but not the 1284p, go figure. I've tried all week.

I use an Ethernet Shield (no SD) and i power it with 3.3 v, connect the ground of course. Then, i wire pins 10, 11, 12 and 13 to the 1284p 4, 5, 6, 7  like this 10->4, 11->5, 12->6, 13->7
The 1284p operates correctly until it hit line Ethernet.begin(mac)
It freeze right there.

Like i said, i do the same thing for months with other megas and it is all fine.
FYI, i've also tried Jeelabs Ethercard, using ethercard library, diferents SS_pin but same problem. Again, works fine with other megas.

Thanks for the help.

I figured out it was located in pins_arduino.h

Code:

static const uint8_t SS   = 4;
static const uint8_t MOSI = 5;
static const uint8_t MISO = 6;
static const uint8_t SCK  = 7;

But, i still can't get any basic Ethernet examples to work, it just hang. I've tried with 4 different 1284p, no love.