sbRIO-9632 5V Pin Current (source)

[Nathan_B.]

I am working on a robotics project and I just received the Robotics Starter Kit (DaNI).  It looks like it has it's two encoders powered by the 5V pins on the sbRIO (but I can't find any specs about the encoders and how much current they are pulling).

I am needing to know if I can use the 5V pins to power the encoders that we are going to use.  There will be, at a minimum, 3 of these on the robot at all times for feedback control on our custom motors.  Each one says that it will pull about 27mA which is 9 times the amount of current that a normal DIO pin can source.  I'm assuming the 5V pins can do more but I just don't know how much.

So, how much current can the several 5V pins source?  If it cannot source enough, can I, on my custom breakout board, supply an external regulated 5V?

P.S.  These may be used to power other sensors like accelerometer, gyro, etc.

[Nathan_B.]

It seems I failed to look in the user manual . . . I'll be thoroughly checking there before asking more questions.

The NI sbRIO power supply has a total of 2 A external load at 5 V. This
total includes 200 mA per installed C Series module. For example, if three
C Series modules are installed, only 2 A – (3 × 0.2) = 1.4 A is available for
use on headers P2–P5. Each pin on the headers is rated for 2 A, but a typical
28 AWG ribbon cable is rated for only 225 mA per conductor. The OEM
user is responsible for determining cabling requirements and ensuring that
current limits are not exceeded.

[CMal · Accepted solution]

Nathan,

The 5V lines on the sbRIO can suppply a combined total current of 2A.  There are more details on page 25 of the manual.  Note that the servo motor on the robot is already powered by the 5V line.  I believe it pulls something on the order of 100-200 mA.