Knowledge Base

The XBIO16 board may be powered off the same power supply as the SPLat controller board it serves or off a different supply. The XBIO16 requires a supply voltage of 10-28VDC, with an absolute maximum rating of 32VDC. It typically draws less than 20mA plus whatever current is flowing through the I/O pins (about 5mA per illuminated LED at 24V, proportionally less at lower voltages).

Note: If you use two power supplies, the expansion board(s) must be powered up at the same time as, or before, the controller.

It is absolutely essential that none of the current from the external loads or inputs flows through the cable back to the controller. For this reason the 0V pin on each XBIO16 I/O connector must be wired independently back to the main power supply. If you use separate power supplies you must tie their negative (0V) terminals together and to the 0V terminals of the controller and XBIO16. If you fail to do this you will at best experience erratic performance and at worst damage either the XBIO16, the controller board or both.

You can supply power for the board itself via the 2-pin power connector. Note that the + pins on the power and I/O connectors are joined together on the board, as are the 0V pins. It is a good idea to separately wire all 0V pins back to the power supply common. You can use the + pin on the power connector to power the board, and then use the + pins on the I/O connectors to feed power to the loads.

Why would you use separate power supplies?

The output circuits on the XBIO16 contain clamps diodes connected to the + supply pin. These are there to prevent damage when switching inductive loads like relay coils. Under Connecting output devices you will find a diagram of how an inductive load is connected (load B, with a parallel diode). The diode on that diagram is replicated on the board (we still recommend an external diode to reduce switching noise). The diode must be connected to the same + supply as the load. For that reason, the XBIO16 + supply pin must be connected to the same power supply as the load (even if you are driving non-inductive loads).

If, for any reason, you need to power the controller off a voltage other than that driving the loads on the XBIO16, you can use two different power supplies providing you observe the above rules.