A simple Hbridge built with:
2x BD177 transistor
2x BD178 transistor
4x IN4007 diode
DC 3/36v 3A continuous e 7A pulsed.
Controlled by arduino, here for code and schematics:
http://www.gioblu.com/tutorials/azionamenti/208-cose-il-ponte-ad-h-e-come-si-costruisce
The robot in the side is Pico base kit see:
http://www.gioblu.com/prodotti
, https://i.ytimg.com/vi/BgdvaLVtr8Y/hqdefault.jpg
source
Scusate, ma il codice da voi fornito è errato !