Galil DMC-13X8 user manual Input Circuit, Sinking Sourcing

Input Circuit

1/4 NEC2505

To DMC-1748* I/O

DMC-1748* GND

I/OCn

1/8 RPx4

x = bank number 0-7

n = input number 17-80

I/On

Connections to this optically isolated input circuit are done in a sinking or sourcing configuration, referring to the direction of current. Some example circuits are shown below:

	Sinking		Sourcing
I/OCn	+5V	I/OCn	GND
I/On	GND	I/On	+5V
	Current		Current

There is one I/OC connection for each bank of eight inputs. Whether the input is connected as sinking or sourcing, when the switch is open no current flows and the digital input function @IN[n] returns 1. This is because of an internal pull up resistor on the DMC-13X8. When the switch is closed in either circuit, current flows. This pulls the input on the DMC-13X8 to ground, and the digital input function @IN[n] returns 0. Note that the external +5V in the circuits above is for example only. The inputs are optically isolated and can accept a range of input voltages from 4 to 28 VDC.

Active outputs are connected to the optically isolated inputs in a similar fashion with respect to current. An NPN output is connected in a sinking configuration, and a PNP output is connected in the sourcing configuration.

	Sinking			Sourcing
I/OCn		+5V	I/OCn		GND
I/On		NPN	I/On		PNP
	Current	output		Current	output

Whether connected in a sinking or sourcing circuit, only two connections are needed in each case. When the NPN output is 5 volts, then no current flows and the input reads 1. When the NPN output goes to 0 volts, then it sinks current and the input reads 0. The PNP output works in a similar fashion, but the voltages are reversed i.e. 5 volts on the PNP output sources current into the digital input and the input reads 0. As before, the 5 volt is an example, the I/OC can accept between 4-28 volts DC.

Appendices • 192 USER MANUAL