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RedLab® 1008
miniLAB 1008 User's Guide
Functional
Details
+5V
+GND
DIO0
Figure 4-8. Digital connection DIO0 detecting the state of a switch
Additional information on digital signal connections
For general information regarding digital signal connections and digital I/O techniques,
refer to the Guide to Signal Connections (available on our web site at
refer to the Guide to Signal Connections (available on our web site at
).
Power terminals
The PC +5V connections on the screw terminal draw power from the USB connector.
The +5 V screw terminal is a 5 volt output that is supplied by the computer.
The +5 V screw terminal is a 5 volt output that is supplied by the computer.
Caution!
The +5 V terminals are outputs. Do not connect an external power supply to a
+5 V screw terminal, or you may damage the device and possibly the computer.
+5 V screw terminal, or you may damage the device and possibly the computer.
The maximum total output current that can be drawn from all miniLAB 1008
connections (power, analog and digital outputs) is 500 mA. This maximum applies to
most personal computers and self-powered USB hubs. Bus-powered hubs and notebook
computers may limit the available output current to 100 mA.
connections (power, analog and digital outputs) is 500 mA. This maximum applies to
most personal computers and self-powered USB hubs. Bus-powered hubs and notebook
computers may limit the available output current to 100 mA.
Just connecting the miniLAB 1008 to your computer draws 20 mA of current from the
USB +5V supply. Once you start running applications with the device, each DIO bit can
draw up to 2.5 mA, and each analog output can draw 30 mA. The maximum amount of
+5 V current available to the user is the difference between the total current requirement
of the PMD (based on the application), and the allowed current draw of the PC platform
(again, 500 mA for desktop PCs and self-powered hubs, or 100 mA for bus-powered
hubs and notebook computers).
USB +5V supply. Once you start running applications with the device, each DIO bit can
draw up to 2.5 mA, and each analog output can draw 30 mA. The maximum amount of
+5 V current available to the user is the difference between the total current requirement
of the PMD (based on the application), and the allowed current draw of the PC platform
(again, 500 mA for desktop PCs and self-powered hubs, or 100 mA for bus-powered
hubs and notebook computers).
With all outputs at their maximum output current, you can calculate the total current
requirement of the miniLAB 1008 device's USB +5 V as follows:
requirement of the miniLAB 1008 device's USB +5 V as follows:
(miniLAB 1008 @ 20 mA) + (4 DIO @ 2.5 mA ea) + (2 AO @ 30 mA ea ) = 90 mA
For an application running on a PC or powered hub, this value yields a maximum user
current of 500 mA − 90 mA = 410 mA. This number is the total maximum available
current at the PC +5 V screw terminals. Measurement Computing highly recommends
that you figure in a safety factor of 20% below this maximum current loading for your
applications. A conservative, safe user maximum in this case would be in the
300-320 mA range.
current of 500 mA − 90 mA = 410 mA. This number is the total maximum available
current at the PC +5 V screw terminals. Measurement Computing highly recommends
that you figure in a safety factor of 20% below this maximum current loading for your
applications. A conservative, safe user maximum in this case would be in the
300-320 mA range.
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