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Revision to Power Wiring

Tony

The Duet boards are designed to power the heated bed (or the solid-state relay controlling it) from the same power supply as they power everything else. The Duet 2 is able to supply 18A to a heated bed (15A on Duet 2 from revision 1.04 on due to the rating of the fuse). If you still want to use a second supply to power the bed (still not exceeding the 18A the Duet can sink), it is possible to arrange this; see [[Wiring and hardware differences from RAMPS etc]] for details.
-== Standby power ==
+== 5V power ==
The Duet operates on two power circuits: a 5V circuit that powers the CPU, WiFi, and web interface, (mostly through a 3.3V LDO) and a 12/24V circuit that powers the motors and heaters.
5V power can be supplied in three ways:
-* From USB ( whether or not an external power supply is attached). This is normally used for initial setup but is not required for normal operation. Note that USB current is limited by older [https://en.wikipedia.org/wiki/USB#Power] to 500mA. Keep this in mind if you are running a [[PanelDue]], especially the 7Inch version which requires more current than this. Some more modern USB ports and USB hubs will supply more than 500mA.
+* From USB ( whether or not an external power supply is attached). This is normally used for initial setup but is not required for normal operation. Note that USB current is limited by [https://en.wikipedia.org/wiki/USB#Power|the original USB specification] to 500mA. Keep this in mind if you are running a [[PanelDue]], especially the 7Inch version which requires more current than this. Some more modern USB ports and USB hubs will supply more than 500mA.
-* From the 12/24V supply through the internal switching regulator. The regulator is enabled if the INT 5V_EN jumper is fitted, as shown here:
+* From the 12/24V supply through the internal switching regulator. This is the most typical way of providing the 5V supply but it means the board is only powered when VIN is present. The regulator is enabled if the INT 5V_EN jumper is fitted, as shown here:
[image|429|align=center]
[image|430|align=center]
-If the main PSU supports an ATX-style PS_ON pin (power supply on when pin is connected to ground), the Duet 2 can enable and disable the main power as needed. Obviously this will not work if the only source of 5V is the 12/24V circuit you are switching; you must either supply USB power or use the 5V in pin from a supply that is not shut down when the 12/24V supply is. On an [https://en.wikipedia.org/wiki/ATX#Power_supply] which provides this function.
+If the main PSU supports an ATX-style PS_ON pin (power supply on when pin is connected to ground), the Duet 2 can enable and disable the main power as needed. Obviously this will not work if the only source of 5V is the 12/24V circuit you are switching; you must either supply USB power or use the 5V in pin from a supply that is not shut down when the 12/24V supply is. On an [https://en.wikipedia.org/wiki/ATX#Power_supply|ATX power supply] which provides this function.
If you are using an external relay to control mains power to the PSU, you can wire either the +5v or +3.3v (depending on what your relay requires) outputs from the duet in to the positive terminal of the relay, and wire the ground terminal of the relay to the PS_ON output on the duet. If you are using a mechanical relay and it does not include a flyback diode of some sort, you will need to wire one in parallel with the relay signal.
[/code]
-'''Note''' If the M80 command is inserted into the config.g file and +5V VSB ( standby) power is connected, you can not switch off the board by
-
-doing a reset, as after reset the config.g is read and the board powered on again.
-
-On the web interface there is a button for toggling the external supply:
+'''Note''' If the M80 command is inserted into the config.g file and +5V VSB ( standby) power is connected, you can not switch off the board by doing a reset, as after reset the config.g is read and the board powered on again. On the web interface there is a button for toggling the external supply:
[image|431|align=center]

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