Discussion on Power Supplies

There are several modifications proposed to the first scheme circulated by Sandor.

Sandor proposes to use only one power supply per unit, providing the 2.5 V, while the 1.25 V is derived by means of a linear regulator. This solution is better from an electrical point of view, and allows in principle up to 60 units to be built, using the available power supplies recuperated from the DELPHI HPC.

Russel requires to have an additional external input to the interlock box: this input is meant for an interlock coming from the cooling unit.

Wacek has several requirements:
- The temperatures and humidities used as input to the interlock pcb, as well as the two voltages and currents, could be made available in an output connector, to be placed on the rear panel of the box, for possible monitoring
- Such output should be isolated, to avoid injecting noise in the system
- In the petal there is a substantial voltage drop in the InterConnect Bus, so the scheme with the limiter placed outside the pcb will not work. Therefore the interlock scheme has to be changed completely: most likely the solution is to use the voltage sense wires for the interlock, and to modify the power supplies so that it reacts quickly to the signal of the sense wire.

Conclusions
Sandor will work (hard!) to a new design that incorporates all the features requested. Obviously, it will take a bit longer to have it finalized, as the design is now substantially more complicated, and it will also cost more than anticipated. A first prototype, without any fancy feature (i.e. without the interlocks) will hopefully be ready in a short timescale, and will be tested to validate the design. If no unexpected problem arises, and if all the DELPHI power supplies turn out to be usable, it should be possible to build enough power supply units to serve TOB and TEC, in time for the startup of the rod/petal production.