Another 2 questions please:
1. To connect the RPi, I need also to connect MicroUSB or the 24V transporter is enough ?
2. Can I use Heatsticks with the OpenSprinkler Board? (or it will not fit?)
1. The 24V transformer is all you need. The OSPi board provides power to the Pi via the GPIO pins.
2. Heatsinks should fit the Raspberry Pi sits on top of the OSPi.