How many judges sat on Galileo's trial over heliocentrism and who were they exactly?
The seven who convicted were 
Felice Centini, Desiderio Scaglia, Antonio Barberini, Berlinghiero Gessi, Fabrizio Verospi, Guido Bentivoglio and Marzio Ginetti. And as you note Francesco Barberini, Laudivio Zacchia and Gaspare Borgia did not. These three didn't vote to acquit, they were just absent from the signing of the condemnation - we don't know why

All information from The Galileo Case: Trial, Science, Truth page 142
By Mario D'Addio. Gracewing Publishing, 2004 ISBN 9780852446652