USB-AD16f
Page 4
4.2
Interfacing examples for digital inputs
The 3.9k
Ω
pull-down resistor sets the input to
low
if no voltage is applied there.
4.2.1
Connecting an optocoupler
Optocouplers provide optimum protection
at each input line. With them, it is possible
to connect higher voltages and to protect
the hardware from being destroyed.
In this regard, please also see application
examples of the optocoupler you use.
Optocoupler boards with 8 or 16 inputs
are available at bmcm.
4.2.2
Connecting a push-button /
switch
Please make sure to use a push-button with
debounce protection, because otherwise
several pulses might be recorded.
The 3.9k
Ω
pull-down resistor is absolutely
necessary to create a defined low signal!
4.2.3
Connecting a voltage divider
If connecting a DC voltage higher than 5V,
a voltage divider must be used so that 5V
at the maximum are applied at the device
input. Exceeding the 5V input voltage
might cause damages to the device.
The relation between the two resistors to be
used is calculated with the following
formula:
U/U
1
= (R
1
+R
2
)/R
1
Input voltages less than 5V are also
sufficient (
high
≥
3V).
