Oh and my drivers also needed a 5V enable line (or more precisely I should say are current limited and expected a 5V enable line, but can be used with 24V if you add resistance). I used the output of the safety circuit (OSSD) to enable the drivers, but that also requires you to have a safety circuit override button incase you need to move anything to resolve a fault condition. Look at my build log, I've been discussing the enable line and the resistors required in the most recent couple of pages.