number physical stations one bus segment 32, defined the RS-485 standard. That means that the power supply unit the beginning the line has to
provide higher voltage compensate the voltage drops due the line resistance.
The calculation with the scheme below takes into account:
- The most distant slave situated the end the scheme -needs least: 19,2 VDC
- Line resistance (0.2 V
Supply current typ.5 mm2) (can changed): 0,075 Ohm/m
Additional info:
max. 19. PDQ22 mA
To simplify the calculation the scheme below uses the highest the currents but the other
hand does not regard the increased copper resistance and voltage drop for higher environment
temperatures.0
The power supply has always fused with max.
All slaves even the slave ost distant from the supply unit need supplied with min.2 31. output voltage above recommended supply unit V
FieldBusPlug 03.
That means: For more than slaves additional segment (coupled with repeater) has be
provided that needs normally separate supply unit.
In accordance with this fact the calculation below provides max slaves one master. Normally
each repeater and RS-485 fiber-optic converter represent also one physical station each the
RS-485 bus line.PDP21-FBP PROFIBUS DP-V0 FieldBusPlug
PDP22-FBP PROFIBUS DP-V1 FieldBusPlug
PDQ22-FBP
Power Supply via Bus Cable, Calculation
Supposed all devices are supplied externally, the supply has feed the PDP21, PDP22 PDQ22
connected the bus.2006 PR0FIBUS-DP_PowerSupply-via-Bus-Cable_Calculation-Berechnung_05-2006. PDP22, PDP21 mA
Supply current typ.2
V including ripple.xls PROFIBUS. (M12 System Limit)
Remark:
The max.
Power Supply 24V adjustable Order code: 1SVR423416R0100 Type: CP-24/5. The supply current depends the voltage (typical values):
Supply voltage: 19
