NPN and PNP are directional attributes of solid-state transistors. These transistors have current amplification capability and are used as switches in a PLC. Devices connected to the PLC must be specified as NPN or PNP. More and more devices today are of the NPN category as they are easier to manufacture and perform better under most conditions.

NPN I/O only         F2424, All T100MD+, Exp4040, E10-npn+, T22H-npn, T28H-Relay, T44H-npn
PNP I/O only         E10-Relay+, T44H-pnp
Both NPN & PNP     F1616-BA, All T100MX+, T40H-Relay, T64H-Relay, EXP1616R

The EXP1616R installation guide has wiring diagram for both NPN and PNP I/O inteface which is applicable to other PLCs as well. You can download it here: http://www.tri-plc.com/inst-exp1616r.pdf for a quick reference. 

A transistor output is a solid-state device that handles small to medium amount of current. Most transistor outputs in our PLC range can only handle DC current up to the power supply voltage of the PLC. (i.e. either 12VDC or 24VDC).

A relay is an electrically operated switch. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contacts. This means that relays allow one circuit to switch a second circuit which can be completely separate from the first. If you need to switch AC voltages such as 24VAC, 110VAC or higher, you need to select a PLC with RELAY output.

The following TRI PLCs and Expansion boards incorporate relays in their output:

F1616-BA, EXP1616R, T100MX3224R+, E10-Relay+, T28H-Relay, T40H-Relay and T64H-Relay.

F-series       You can add digital I/O expansion board to any of the F-series PLCs via the EXP1616R, the EXP4040 or both. Multiple expansion boards can be cascaded to increase the number of digital I/Os up to the maximum limit. By default, all F-series PLCs can be expanded up to 128 inputs and 128 outputs.

T100MD+     You can add digital I/O expansion board to any of the T100MD+ PLCs via the EXP1616R, the EXP4040 or both. Multiple expansion boards can be cascaded to increase the number of digital I/Os up to the maximum limit.  By default, all T100MD+ PLCs can be expanded up to 96 inputs and 96 outputs. T100MD+ CPU with firmware  version r47 or later supports up to 128 inputs and 128 outputs using the SETSYSTEM 16,16 to override the default limits.

T100MX+     The current T100MX+ PLC comprises two models: T100MX3224R+ and T100MX4832+ and they are not expandable.

E10+           The E-series is intended to be a small application controller and as such is not designed for expandability.

H-Series     The H-series has sufficient models for I/O range up to 64 and is sufficient for most applications; no expandability has been designed in.

How can I connect REMOTE Digital  I/Os to TRi PLCs?All F-series and M-series Super PLCs (i.e. F2424 & F1616-BA, All T100MD+ & T100MX+) can act as a communication master to other TRi PLCs or to third party devices that support RS485 communication protocol such as Modbus. As such, the F-series/M-series Super PLC can easily use any other F-series, M-series, H-series or E10+ PLCs as its remote I/O. The E10+ being small and low cost are ideal to be deployed in a wide area network as remote I/Os as shown below:

The TBASIC language incorporates a special command "NETCMD$" which can be used to monitor/control any device that employ ASCII based protocol (including all TRi PLCs' native hostlink command). TBASIC also has built-in READMODBUS and WRITEMODBUS commands which can be used to interface to any RTU that supports Modbus RTU protocol.

A DIGITAL signal is a simple signal that is usually just ON or OFF.

An ANALOG signal has variations that are meaningful such as inputs or outputs relating to level of temperature, light, sound, pressure, position, etc.

Most sensors produce very weak signal which needs to be amplified by special purpose instrumentation amplifier called "Signal Conditioner" and the outputs from the signal conditioner can then be connected to the PLC's analog inputs.

A Pulse Width Modulated (PWM) signal is a special method that produces a variable voltage using an ON/OFF type digital I/O. It is neither a pure digital nor a pure analog I/O and is discussed in the following FAQ question.

A Pulse Width Modulated (PWM) signal uses the duty cycle of a rapidly switching digital I/O to represent a time-average variable. For example, if you turn ON a digital output for 10ms, then turn it OFF for 90ms, and repeat this cycle indefinitely, what you produce will be a rapidly pulsating waveform with a 10% ON duty cycle. If you use a volt-meter to measure the output voltage of this waveform, what you will get is a time-average reading which is equal to 10% of the peak voltage output when the digital output is fully turned ON.

Likewise, you can measure a PWM input signal by measuring the ON time of the incoming pulses (the PULSEWIDTH), then divide it by the period of the pulses (the PULSEPERIOD) to obtain the duty cycle. The actual measured quantities = duty cycle x Full-Scale value.

The applications that need analog I/Os range widely, but some of the more common ones in industry relate to the measurement and control of temperature, air/fluid flow and motor speeds.

For example, if you are trying to determine if something is present or absent, you only need a digital input. But if you are trying to measure the temperature in your room, you will need an analog input to the PLC.

Likewise, if your only means of controlling a heater is to turn it ON or OFF, then you just need a digital output. But if you have the ability to control the speed of a motor by applying a variable voltage of say between 0 to 5V DC, then you need an analog output from the PLC.

All the F-series Super PLCs include built-in 4 channels of PWM output and a number of analog I/Os as shown in the following table:
The F1616-BA has 12 Analog I/Os :
- 8 x AI - 12-bit 0-10V
- 4 x AO - 10-bit 0-10V
The F2424 has 12 Analog I/Os :
- 8 x AI - 12-bit 0-5V
- 4 x AO - 10-bit 0-5V

All the M-series Super PLCs include built-in 2 channels of PWM output and a number of analog I/Os as shown in the following table:
The T100MD1616 has 5 Analog I/Os :
- 4 x AI - 10-bit 0-1V x2 and 0-5V x2
- 1 x AO - 8-bit (0-20mA)
All the other M-series PLCs have 8 Analog I/Os :
- 6 x AI - 10 bit, 0-5V
- 2 x AO - 8 bit, 0-5V

None of the H-series and E10 PLCs has analog I/Os and they also have no means of interfacing to third party analog I/Os.

You can use a second, third or more T100MD888+ PLC to provide additional low cost analog I/Os and 2 channel of PWMs per PLC to a master F-series or M-series Super PLC. The master and slave PLCs communicate using their built-in RS485 interface over a low cost two-wire bus. There are built-in TBASIC commands to facilitate master/slave communications. Please see the following webpage for more details: http://www.tri-plc.com/ioboard.htm#mstslave

If you require higher resolution analog I/Os, TRi carries a range of I-7000 series Analog I/O modules  that provides multiple channel of 16-bit analog inputs as well as 12-bit or 14-bit of analog output.