Let's Make Robots!

H-bridge HELP NEEDED ! ! ! ! !

I searched every shop in my area couldnt find a single piece of H.so i thought to make it with logic gates as 7400 series is available. but before i buy i wanna know if my design is feasible? and is there any possibility of damaging of chip (logic gates).i'm using a GEARED MOTOR in my H-bridge


Buyed a severino some days ago..bt can't figure out how to establish a connection between computer and the severino.i have a USB to serial converter..(comp-->usb--->db9-->RS232-->severino).windows found new hardware,installed the drivers.bt still no LED s ar glowing.And arduino ide cant send data to the chip..do i need any external power supply?plzz plz help