Terminal 1
Terminal 1 provides power input, serial communication (RS485 and RS232), and isolated digital outputs.
Power Supply Input
Specifications
| Parameter | Minimum | Maximum | Unit |
|---|---|---|---|
| Input Voltage | 10 | 30 | VDC |
| Surge Protection | - | 60V for 20ms | - |
| Fuse Protection | - | 4A replaceable | - |
Wiring
Connect DC power supply to Terminal 1:
- + terminal: Positive voltage
- - terminal: Ground/negative
No earth connection is required.
Fuse Protection
The power input is protected by a 4A fuse on the internal board. If the device fails to power up:
- Check power supply voltage (must be 10-30V DC)
- Inspect the 4A fuse on the internal board
- Replace fuse if blown
Surge protection handles transient overvoltages up to 60V for duration of 20ms.
Isolated RS485
Specifications
| Parameter | Value |
|---|---|
| Maximum Baud Rate | 500 kbps |
| Isolation Voltage | 5000 Vrms |
| Direction Control | Automatic |
| Device Mapping | /dev/ttyACM0 |
Wiring
Minimum connection (2-wire):
- A - RS485 A signal (positive differential)
- B - RS485 B signal (negative differential)
Recommended connection (3-wire):
- A - RS485 A signal
- B - RS485 B signal
- 485-GND - Ground reference (improves noise immunity)
Termination Resistor
A 120Ω termination resistor is available via internal DIP switch.
When to enable termination:
- Device is at the end of the RS485 bus
- Both ends of the bus should have termination enabled
When to disable termination:
- Device is at an intermediate position on the bus
Isolation
The RS485 interface is isolated from:
- System ground
- Other terminals and interfaces
Isolation rating: 5000 Vrms
Isolated RS232
Specifications
| Parameter | Value |
|---|---|
| Maximum Baud Rate | 120 kbps |
| Isolation Voltage | 3000 Vrms |
| Device Mapping | /dev/ttyACM1 |
Wiring
3-wire connection:
- Tx - Transmit data
- Rx - Receive data
- 232-GND - Ground reference
Isolation
The RS232 interface is isolated from:
- System ground
- Other terminals and interfaces
Isolation rating: 3000 Vrms
Isolated Digital Output
Specifications
| Parameter | Minimum | Maximum | Unit |
|---|---|---|---|
| Output Voltage | - | 50 | V |
| Output Current | - | 500 | mA |
| Isolation Voltage | - | 1500 | Vrms |
Characteristics
Output type: Dry contact (solid state relay) Load compatibility: DC or AC loads Control logic: Active HIGH Number of channels: 4 (DO0, DO1, DO2, DO3) Isolation: Each channel isolated from system and from other channels
GPIO Mapping
| Output | GPIO Pin |
|---|---|
| DO0 | GPIO23 |
| DO1 | GPIO24 |
| DO2 | GPIO25 |
| DO3 | GPIO26 |
Wiring
Each digital output provides two terminals for dry contact switching:
- Connect load between the two terminals for each output
- Polarity does not matter (AC or DC loads supported)
- Maximum ratings: 50V, 500mA per channel
Example - Controlling a 24V DC relay:
DO0 Terminal 1 ----[+24V DC Power]
DO0 Terminal 2 ----[Relay Coil]----[GND]
When GPIO23 is HIGH, the solid state relay closes and activates the load.
Common Mistakes
Power Input Issues
- Using voltage outside 10-30V range - May damage device or fail to power up
- Exceeding surge limit - Fuse will blow to protect circuitry
- Ignoring blown fuse - Device will not power up via Terminal 1 if fuse is blown
RS485 Communication Issues
- Not connecting GND reference - Can work but reduces noise immunity
- Incorrect termination - Enable only at bus endpoints, not intermediate nodes
- Swapped A/B signals - Reverse polarity causes communication failure
Digital Output Issues
- Exceeding 50V or 500mA - May damage solid state relay
- Expecting common ground - Outputs are isolated; each channel is independent
Source(s):
- IRIV PiControl CM4 User Manual, Rev 1.3, Nov 2025, Sections 2, 4, 5.1