Main/Expansion board 5v power suggestion



  • One of the things I've realized is that if you supply the expansion board from the same Vin as the mainboard and you use ATX control of Vin, the expansion board disappears completely when you issue an M81 because it has no separate 5v power option (I think). This means the sensors disappear with M81.

    I do see a solder pad labelled "5v disable" but I'm not sure where it'd be appropriate to supply 5v externally.

    Anyway, I was thinking that on future boards the mainboard could supply 5v on the unused pins 1 and 6 on the CANbus connector.


  • administrators

    @gtj0 the 5V disable on expansion was to allow for turning elements of for EMI testing on the prototypes. don't feed 5V into that.

    Its a good point about not having an external 5V supply. for low current only applications it might be possible to do as you suggest and send power down the 1&6 connectors on the RJ11 but we don't plan to currently.


  • administrators

    What would be the purpose of keeping the expansion boards powered with 5V? And what is the purpose of turning off VIN power but keeping 5V?



  • @T3P3Tony said in Main/Expansion board 5v power suggestion:

    @gtj0 the 5V disable on expansion was to allow for turning elements of for EMI testing on the prototypes. don't feed 5V into that.

    Nah, I wasn't planning to feed 5v there. I don't see the wiring diagram for the expansion board so I was really wondering if that disabled the 5v regulator and might allow us to feed 5v via another pin.

    Its a good point about not having an external 5V supply. for low current only applications it might be possible to do as you suggest and send power down the 1&6 connectors on the RJ11 but we don't plan to currently.

    Just a thought for the future.

    @dc42 said in Main/Expansion board 5v power suggestion:

    What would be the purpose of keeping the expansion boards powered with 5V? And what is the purpose of turning off VIN power but keeping 5V?

    Same as for the mainboard. Keep the electronics hot but save power by turning off Vin. Also for letting the kinematics "freewheel" it's easier to do a M81/M80 or click a button on the DWC than issue an M18, then a zero move to start them again. And for keeping the sensors active of course. Without Vin on the expansion board, you'd lose its temps, endstops, etc.but you'd still have them on the mainboard. Oh yeah, you can't update firmware without Vin on the expansion board but you can on the mainboard.


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