2
•
COM
–
The common (COM) is connected to ground. When an arrival occurs, current will flow
through the signal (SIG) connection to ground. There is 100 Ohms of impedance in this path to
limit the current.
This output can be used with controllers that support a dry contact or voltage input.
2.2.1
Dry Contact Input
The Sasquatch has been designed with an open collector field effect transistor (FET) so that it acts as a
dry contact, which ensures that it can be connected directly to most controllers. Most magnetic sensors
available on the market are designed to act as a dry contact, so the Sasquatch can easily be used as a
replacement sensor for any system. A dry contact input on a controller features an internal pull up
resistor. When the contact is open, the internal input will read the system voltage. When the contact
closes, the input will now read ground.
ETC Controller
100k
Ω
5 V
PWR
SIG
COM
Sasquatch
PWR
SIG
COM
100
Ω
To Input
Figure 2 - Typical Dry Contact Interface
2.2.2
Voltage Input
When using a programmable logic controller (PLC) or other application specific controller (i.e. Flow
Computer) it is possible that you need to connect to a voltage based input. This type of input is
expecting to see a change in the voltage and is not directly compatible with the Sasquatch because it
closes a switch instead of sending back a voltage. The difference is that there is no internal pull up
resistor provided by these controllers, so an external pull up resistor must be connected. Connecting a
100k
Ω
resistor between the power and input on the controller will allow these systems to connect to a
Sasquatch.
When the Sasquatch switch is open, the input will see the voltage coming from the power connection.
When the switch closes, the input will be pulled to ground. This difference in voltage can then be
detected.
Controller w/ Voltage Input
100k
Ω
5 - 24 V
PWR
SIG
COM
Sasquatch
PWR
SIG
COM
100
Ω
To Input
Figure 3 - External Resistor for Voltage Input
