Masive Dual Motor driver Build

Hi..

I'm new to the Forum, new to Arduino's and new to electronics.
So please be patient with me.

The DC motor drivers on the market are too expensive for my pocket, so I want to build my own.
This will also be a great learning curve in electronics.

I'm building an autonomous robot using a 1/16 Heng long Tiger 1 as base.
According to the stuff I read on Google and a bit of self experience,
I've noticed that the motors in this tank can pull as much as 5A (7.2V) at Stall...
The only "shield" I could find that can handle this is the T'rex motor driver. (zaR 1200)
The Rover 5 Control Unit is so on the edge - Witch makes it affordable but risky...

If anyone has advice so far... Please make my day.

My plans are to try and build a double H-bridge motor driver with Mosfets (IRF540)
but they have a high threshold voltage so I plan to add IC ULN2803.

I want to put the Arduino pins on the ULN2803 input.
And then use the IC to put 7.2V on the Mosfet H-bridge.

Some things I worry about:
Is there a "better" Mosfet to use? (7A+ needed)
Is the 6-7.2V enough to Gate the Mosfets?
Is the Diode in the Mosfet good enough?

I will pull up a schematic and post it as soon as I get time.

Thanks for the help :smiley:

IRF540 need 10V gate drive.

You should do some careful research before launching into a high-current
H-bridge powered by batteries (presumably LiPo?). So very easy to zap
MOSFETs through over current if you get things wrong.

Have you seen the Pololu high current driver boards? http://www.pololu.com/product/2507

BTW when selecting MOSFETs first choose an appropriate high enough (but
not too high) voltage rating, then the Rds(on) you need. You won't normally
have to worry about the current rating as its a thermal limit under infinite
heatsink.

If using PWM then good driving circuitry is needed to ensure fast switching,
otherwise the MOSFETs will cook. An ULN2803 may not be fast enough,
and more importantly cannot pull its output down to 0V so it cannot drive
low-side MOSFETs at all - use logic-level for low-side?

Too expensive?

14A / 30A peak / $11
The only downside is that it is limited to 16V.

Note that 'goodluckbuy' has it mislabeled. It is not a stepper driver, it is a dc motor driver.
More info: