if the circuit have a voltage regulator on 5V i can choose between the power sources right?/QUOTE]The Mitsu controller has a regulated 5V source already, which I assume can be used to drive the timing circuit. However, the digi-pot output impedance (10k) is probably too high to provide the speed control voltage drive directly, which is why I have included the LM324 buffer stage in the design. To enable the full 5V drive range to be achieved the buffer stage needs a higher supply voltage than 5V; hence the 9V regulator in the revised design.
You seem reluctant to use the existing 24V Mitsu controller supply