D3J0308 Modbus
8-input/4-output Modbus-RTU/RS-485 I/O module with relay or transistor outputs, local interlock and emergency braking.
🔍 Click to enlarge · 1/3Technical Specifications
| Type | ASIC-based Modbus-RTU/RS-485 digital input/output module (8 inputs + 4 outputs) |
|---|---|
| Default order code | D3J0308M111 (all-relay output, pulse unavailable, no wireless) |
| Product ID / default slave address code | 0x3308 |
| Input channels | 8 fully isolated digital inputs, plus 2 analog input channels and 1x 5V/100mA sensor supply output |
| Output channels | 4 fully isolated digital outputs (relay type or transistor type, selectable), plus up to 2 pulse PWM/PTO outputs |
| Communication interface | RS-485 (Modbus-RTU); USB port included; optional 2.4GHz wireless MODBUS-OTA |
| Default baud rate | 9600bps |
| Default data format | 8 data bits, even parity, 1 stop bit |
| Default slave address | 0x02 |
| Selectable baud rates | 300 / 600 / 1200 / 1800 / 2400 / 4800 / 7200 / 9600 / 14400 / 19200 / 28800 / 38400 / 56000 / 57600 / 76800 / 115200 |
| Selectable parity | None / odd / even (default even) |
| Selectable stop bits | 1 (default) / 1.5 / 2 |
| Slave address range | 1-247 (0x01-0xF7) |
| USB mode address | Fixed at 0x01 when USB is connected; RS-485 then switches to master mode |
| Input threshold | Approx. 3V (above = high level, below = low level) |
| Input counting | Each channel (DINnCNT) increments on rising edge, rolls over at 65535, resettable by write |
| Input filtering | Each channel (DINnFLT) has an independently adjustable debounce filter (0 = off), setting persists across power loss |
| Auto-reporting | Supports periodic or change-triggered reporting (AT format) over USB or RS-485; default off |
| Read/write function codes | 0x02 read discrete inputs; digital outputs (DOUTnDV) read/written via holding registers (0x03/0x06/0x10); also 0x04 read input registers, 0x16 mask write, 0x17 read/write multiple registers, 0x11 report device ID |
| Configuration protection | Write ASCII "UL" to the lock register before modifying sensitive registers (name/serial port/wireless); automatically re-locks after each write |
| Supply voltage | DC 11-28V |
| Supply ripple | < 1Vp-p |
| Supply current | < 1500mA |
| Communication terminal stress (normal) | DC 0-5V |
| Input terminal stress (normal) | DC 0-30V |
| Output stress, relay type (normal) | DC 30V or AC 0-220V, 8A |
| Output stress, standard transistor type (normal) | DC 12-48V, 8A |
| Output stress, high-speed transistor type (normal) | DC 12-24V, 8A |
| Communication isolation voltage (normal) | < 250V |
| Input isolation voltage (normal) | < 250V |
| Output isolation voltage, relay type (normal) | < 250V |
| Output isolation voltage, transistor type (normal) | < 130V |
| Operating temperature | -20 to 60 degrees C |
| Supply voltage (absolute maximum) | DC 28V |
| Fuse (one-time) | DC 250V, 3000mA, slow-blow |
| Communication terminal stress (absolute maximum) | DC 50V |
| Input terminal stress (absolute maximum) | DC 50V |
| Output stress, relay type (absolute maximum) | DC 30V or AC 0-220V, 8A |
| Output stress, standard transistor type (absolute maximum) | DC 55V, 10A |
| Output stress, high-speed transistor type (absolute maximum) | DC 40V, 10A |
| Communication / input isolation voltage (absolute maximum) | DC 1000V, 60s (type test) |
| Output isolation voltage, relay type (absolute maximum) | DC 1000V, 60s (type test) |
| Output isolation voltage, transistor type (absolute maximum) | DC 250V, 60s (type test) |
| Relay mechanical life | > 100,000 operations (> 10,000 under heavy load) |
| Storage temperature | -40 to 85 degrees C |
| ESD immunity | IEC 61000-4-2: 4kV discharge on all terminals - normal operation (A) |
| EFT immunity | IEC 61000-4-4: 2kV/5kHz/2min - normal operation (A); 4kV/5kHz/2min - no permanent damage (C) |
| Surge immunity | IEC 61000-4-5: 1kV to ground on all terminals - no permanent damage (C) |
| Creepage distance | > 6.5mm measured (requirement > 6mm), pollution degree 3, material group IIIa/IIIb |
| Electrical clearance | > 2.2mm measured (requirement > 2mm) |
| Input/output response time | Typical 20ms |
| Serial command reply time | Maximum 25ms |
| Module dimensions | 107 x 88 x 59mm (tolerance +/-5%) |
| Terminal pitch | 5.08mm |
| Terminals | 26 screw terminals, plus indicator LEDs, 1 USB port and 2 internal analog input leads |
Overview
The D3J0308 is an 8-input/4-output Modbus-RTU/RS-485 digital I/O module built around an ASIC core, for engineers who need one device to both read a bank of switches, limit sensors or alarm contacts and drive relay or transistor loads from the same RS-485 bus. It combines 8 fully isolated digital inputs with 4 fully isolated digital outputs on a single board, so a controller can poll input states and command outputs without wiring separate input and output modules.
The module runs on DC 11-28V supply, communicates by default at 9600bps/8-even-1 over RS-485 Modbus-RTU with a slave address range of 1-247, and each output channel can be ordered as relay type (DC 30V or AC 0-220V, 8A) or open-drain transistor type (DC 12-48V, 8A, with a built-in 10A freewheeling diode). It also ships with a USB port supporting MODBUS-ASCII and AT commands, plus 2 bonus analog input channels, up to 2 high-speed PWM/PTO pulse outputs, and a 1-channel 5V/100mA sensor supply, with an optional 2.4GHz wireless MODBUS-OTA.
Features & Benefits
Two Modules' Worth of I/O in One 107mm Body
8 fully isolated digital inputs and 4 fully isolated outputs share one ASIC core, one RS-485 drop and one 26-terminal housing measuring 107 x 88 x 59mm. A separate 8-point input card plus a 4-point output card would need two DIN slots, two power feeds and two bus addresses - this is one of each, so you save panel width, wiring hours and per-point cost at the same time.
Relay or Transistor Output - Same Part, Chosen at Order Time
Order code [ddd] 1st digit picks the output stage: relay type switches DC 30V or AC 0-220V at 8A with contact isolation under 250V, while transistor type is open-drain at DC 12-48V / 8A with a 10A freewheeling diode already on board - so it drives solenoid valves, contactors and DC motors directly without an external flyback diode or interposing relay.
Keeps Running When the Host Doesn't
Each output can be bound to its matching input (output n follows input n) and a limit or e-stop signal can force outputs to a preset safe state through the BRKFLG brake flag, which outranks even host port forcing. If the PLC crashes or the RS-485 cable is cut, the interlock and e-stop still act in a typical 20ms - the safety logic lives in the module, not in the network.
On-Board Timing, Counting and Filtering Offload the Host
Outputs have 5 jog/delay modes that build local sequences (energise on trigger, drop out after a configurable delay) with no ladder code. Every input carries its own DINnCNT rising-edge counter that rolls over at 65535 and its own DINnFLT debounce filter, adjustable per channel and retained through power loss - so a bouncing limit switch is cleaned up in hardware instead of eating scan time on the master.
Analog Inputs, Pulse Outputs and Sensor Power Included, Not Extra
Every unit ships with 2 wide-range analog voltage inputs, a 5V / 100mA sensor supply and up to 2 high-speed PWM/PTO pulse channels (order code [ddd] 2nd digit = 3 or 4). A greenhouse node can power a soil-humidity sensor, read its voltage, run a fan at speed via PWM and switch irrigation on relay outputs - from one module, with no analog card and no separate 5V brick.
Plugs Into Any Modbus Network - and Into None at All
Standard Modbus-RTU over half-duplex RS-485 A/B, default 9600bps 8-even-1, baud selectable 300 to 115200bps, parity none/odd/even, stop bits 1/1.5/2 and slave address 1-247, so dozens of units daisy-chain on one twisted pair and any PLC, HMI or SCADA talks to them out of the box. MODBUS-ASCII suits touchscreens, AT commands suit quick jobs, and optional 2.4GHz MODBUS-OTA covers points you cannot cable to.
Commission It on a Laptop Before the PLC Exists
The included USB port takes over as address 0x01, flips the RS-485 side into master mode and doubles as a USB-to-serial converter - so one laptop plus the supplied PC software can configure the module, drive its outputs and even poll other 485 slaves on the bus. Auto-reporting can push input changes on interval or on change, and sensitive registers stay protected behind an ASCII "UL" unlock that re-locks after every write, so a wrong keystroke cannot lose your serial settings.
Built for the Panel, Not the Bench
EFT immunity is 2kV - double the 1kV that IEC 61000-6-2-2016 asks of industrial gear - alongside 4kV ESD and 1kV surge, with reverse-polarity, overcurrent, surge and automotive load-dump protection on the DC 11-28V supply and a 3000mA slow-blow fuse. The PCB is slotted for creepage: >6.5mm measured against a >6mm requirement, clearance >2.2mm against >2mm. Relays last over 100,000 operations, and for sites with brutal EFT the input-strengthened "XS" version is a suffix away.
Applications
Models & Ordering Information
Base Model
How to Select
- Choose the D3J0308 (8 inputs / 4 outputs) for mid-size machines and distributed stations needing about 5-8 acquisition points and 3-4 drive points, balancing point density with per-point cost in a 26-terminal, ~107mm-long module.
- For fewer points, step down to the D3J0304 (4-in/2-out) or D3J0302 (2-in/1-out); for larger panels needing more than 8 inputs or 4 outputs, step up to the D3J0312 (12-in/8-out).
- Choose transistor output for inductive or high-current DC loads; choose relay output for standard AC loads or where physical contact isolation is preferred.
- When networking multiple modules on one RS-485 bus, set a unique slave address (1-247) on each unit.
- For sites with frequent electrical fast transients (EFT), order the input-strengthened version (order code suffix "XS").
📘 Need the full method? NPN vs PNP Sensor Outputs Explained
When NOT to specify the D3J0308 — and what to use instead
Your panel has more than 8 points to read or more than 4 loads to switch
Why not: D3J0308 tops out at 8 fully isolated digital inputs and 4 digital outputs.
Use instead: Move up to D3J0312 (12-in/8-out), the largest model in the D3J03 family.
You only need to monitor 8 points with nothing to switch, or only switch 4 loads with nothing to read
Why not: D3J0308 always bundles 8 inputs with 4 outputs on its 26-terminal board; a monitoring-only or switching-only application pays for and wires channels it will not use.
Use instead: Use the pure-input D3J0108 or the pure-output D3J0204 module instead.
You are relying on the 4 input-linked outputs plus the BRKFLG brake as a certified safety interlock across several machine zones
Why not: None of D3J0308's outputs are OSSDs and neither the linkage nor the brake (typical ~20ms response) carries a Type/SIL/PL rating. Both run locally on the module without the host, which is exactly why they get mistaken for a safety function, but they are not one.
Use instead: Use a DA31 Emergency-Stop Safety Relay Module or DQSRN Safety Relay Module for any zone that actually needs a rated safety circuit.
Any of the 4 outputs will drive a load over 8A, or an AC voltage above 0-220V
Why not: Both output types are rated for 8A continuous (relay: DC 30V/AC 0-220V; transistor: DC 12-48V normal or DC 12-24V high-speed), with only a 10A absolute-maximum transistor rating even with its built-in flyback diode.
Use instead: Insert an appropriately rated contactor or relay between the D3J0308 output and the load.
Your process needs the 4 outputs to respond to combined or sequenced conditions across the 8 inputs, not the fixed output-n-to-input-n pairing
Why not: D3J0308's onboard logic is limited to that direct linkage, 5 jog/delay modes, and per-channel DINnCNT/DINnFLT counting and filtering - it has no user-programmable logic engine for cross-channel conditions.
Use instead: Use the D4G0206 micro-PLC where genuine programmable logic across many points is needed.
Your SCADA/PLC network runs a fieldbus other than Modbus-RTU
Why not: D3J0308 speaks RS-485 Modbus-RTU by default (9600bps/8-even-1, address 1-247), with Modbus-ASCII, AT commands and an optional 2.4GHz Modbus-OTA wireless link as the only alternatives.
Use instead: Choose an I/O module or gateway native to your fieldbus instead.
Specifications we do not publish yet
We only publish a figure once we are confident it is true. The items below are still being validated through further testing and real-world customer feedback, so for now we would rather leave them open than guess. If one of them matters to your design, ask us for the latest validated status.
- Mean time between failures (MTBF) for the module - not published
- Ingress protection (IP) rating of the enclosure - not stated in the source manual
- Full EMC compliance (radiated/conducted emissions, RF immunity) beyond the documented ESD/EFT/surge results - not published
- Resolution, accuracy and input voltage range of the 2 analog input channels - only described as voltage measurement, no numeric spec given
- PWM/PTO pulse output frequency range and step/pulse-count limits - no numeric value documented
- Wire gauge accepted by the 26 screw terminals - not stated
- Maximum number of RS-485 nodes per bus segment and maximum cable length - not stated
- Module weight (only L x W x H = 107 x 88 x 59mm is given) - not documented
Frequently Asked Questions
What does the D3J0308 do?
What's the difference between the relay and transistor output types?
Can the outputs respond to the inputs without a host controller?
How do I use the PWM/PTO pulse output?
How does input counting and filtering work?
How do I unlock the module to change protected registers?
Does the D3J0308 meet industrial EMC requirements?
Works Well Together
On the same machine or line, D3J0308 is typically ordered together with: Proximity Sensors · Photoelectric Sensors · Laser Distance Sensors
D6.5 Series Inductive Proximity Sensors (Ultra-Short 18mm / Y-Type / 35mm / 45mm)
6.5mm-diameter inductive proximity sensors for tight-clearance mounting where M8 sensors won't fit.
BGS-CX441 / BGS-CX442 Background Suppression Photoelectric Sensor
Wire-adjustable BGS sensor with 2 mm or 15 mm spot, 10-300 mm range, published black/white differential distance.
DDA-Y & DDB-Y Industrial Laser Distance Sensor (Phase-Shift)
Phase-shift laser distance sensors: 0.2-100 m range, millimeter accuracy, RS485 Modbus RTU, switching or analog output.
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