He's tended to wander about, somewhat, hasn't he?

I think some of this has been caused by various contrasting views confusing him in his approach to controlling the drive for his LED's.

To some of us, a "constant-current driver" means a specific component, while to others, myself included, it simply means a driver with precisely controlled constant current. With the one class of component, the constant current is determined by the component. With the other, it is determined by the implementor. That way, the LED supply can be arbitrarily high, in order to accommodate the higher forward voltage of the different-color LED's, still allowing him to use the otherwise adequate ULN2803 darlington that he has and with which he's familiar.

I don't know whether he's considered that he can drive a MOSFET, e.g. IRF640, with a MAX232A (He may well already have those). He won't need the negative voltage, but the voltage doubler will get him the 10 volts he needs to drive his high-current, high-voltage MOSFET.

RE