OEM Controls SB25 - Manual (Page 3)

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2.1.4 Analog Inputs
Analog Inputs are used to measure an external DC voltage in the 0-5V range. Also, this
input can function as a PLC type 4 – 20mA input because the input circuitry was
designed such that a DC input voltage of 5V results in 20mA of input current.
2.1.5 RS485 Communication ( Remote Inputs )
Inter-board communications between the SB25 and other OEM Controls, Inc. SB family
boards such as the SB10 or Digiplexor is accomplished with the RS485 communication
port. Typically, Digital Inputs on a remote board, such as the SB10 or Digiplexor, are
used to control Digital Outputs on the SB25 through the RS485 communication port.
2.2 Outputs
2.2.1 Output Protection
SB25 PWM and Digital Outputs utilize “smart” FET based power transistors that provide
excellent protection against electronic hazards inherent to mobile applications. These
outputs have over voltage, overload, over temperature and short circuit protection. In
addition, they are protected against limited ESD (Electro Static Discharge) and reverse
battery events.
2.2.2 PWM Outputs
Outputs can be configured to drive proportional PWM inductive loads. A PWM Output
will cycle from ON to OFF at a predefined rate (frequency) required by the PWM load.
The percentage of time that the PWM Output is ON is referred to as the Duty Cycle. The
Duty Cycle is varied to control the load. Typically, the Digisensor rotary input sensor
provides the input for one (unidirectional) or two (bi-directional) PWM Outputs.
2.2.2.1 Diode Clamping
A diode clamp is used to limit the back EMF of an inductive PWM load to one diode
drop below ground. This type of clamping is typically used for high current PWM loads
2.2.2.2 Zener Clamping
Certain inductive PWM loads require a very negative back EMF level. A Zener
Clamping configuration is available for all PWM Outputs.
2.2.3 Digital Outputs
Loads that attain an ON or OFF state due to the state of one or more inputs are referred to
as Digital Outputs. Digital Outputs do not cyclically change state but are typically
controlled by inputs. Inductive loads connected to Digital Outputs are clamped and do
not require additional external clamping.
2.2.4 Analog Outputs
Low current analog voltage outputs can be configured to drive high impedance loads that
require voltages in the range of 0-10VDC.