900719_FOCE : FOCE Aux Circuits This page last changed on May 22, 2008 by chadillac. # FOCE Auxilliary Circuits The auxilliary circuits board provides the following functionality: 1. Scaling for source voltages (+12V and +24V) to the DMM32 DAQ board. 2. Current monitoring for the source voltages (+12V and +24V) to the DMM32 DAQ board. 3. Creates a reset pulse for the computer stack from the Axis 241 Video Server. # Source Voltage Scaling The +12V and +24V source voltages are scaled down to 0 to +5V via 1% resistors. This voltage is read by the DMM32 DAQ board. The curve for +24V is: #### Y = 5.622X + 0.025 (where X represents the scaled 0-5V signal and Y represents the actual input source voltage) The curve for +12V is: #### Y = 2.767X - 0.004 (where X represents the scaled 0-5V signal and Y represents the actual input source voltage) # Current Monitoring The outputs of the Vicor DC-DC modules are monitored by current sense ICs (MAX4173). These parts read the voltage across a sense resistor (in series with the monitored voltage), calculate load current and convert that to a usable output voltage. The part was chosen for a gain of 50 with a sense resistor of 10m ohms. This allows for a full-scale load current of 10 amps with a corresponding output voltage of 0-5V. The curve for the +24V load current is: #### #### Y = 1.98X - 0.02 (where X represents the scaled 0-5V signal and Y represents the actual load current in amps) The curve for the +12V load current is: #### Y = 2.027X +0.012 (where X represents the scaled 0-5V signal and Y represents the actual load current in amps) # Computer Stack Reset # Links MAX4173 Auxiliary Circuits Schematic

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