ConnectPort X4H Local IO
From Digi Developer
Contents |
Digi ConnectPort X4H Local I/O
Models
The CPX4 (or X4 NEMA) has 4 internal I/O signals. It comes in 3 variations:
- Four analog inputs (standard stock model)
- Two analog inputs and two digital input/outputs (special order)
- Four digital input/outputs (special order)
In addition, changing XBee module type may result in a large analog signal error (up to 50%) since the ADC converts of different XBee embedded processors measure different voltage ranges. Thus you must purchase the correct CPX4 with the correct XBee technology installed.
Power
The standard CPX4H includes a built-in AC/DC power supply which converts 100-240VAC into 24VDC. The DC ground is fully isolated from the AC supply and chassis ground in the NEMA box.
Sensor Excitation Power
The 14-pin terminal block includes 5 screw terminals (1, 4, 7, 10, and 13) which are labeled as 24VDC output supplies. Each power terminals is limited to about 30mA. If you need more power (for example 24VDC 100mA for a radar sensor), you can tap that power directly from the CPX4H's AC/DC supply. The power available for your sensor use is limited to a total of 24VDC 150mA - use an external power supply if more power is required.
However the actual voltage is related to the direct DC power supplied to the CPX4. The 24VDC value labeled is derived from the CPX4H's built-in AC/DC power supply which converts 100-240VAC into 24VDC. Since the CPX4H itself can run on from 9 to 30VDC, you can also 'adjust' the voltage of the 5 power terminals from 9 to 30VDC by using a different AC/DC supply. So to obtain 15VDC, you would need to power the CPX4H with 15VDC.
This also means if you power the CPX4H from a 12VDC battery or vehicle system, then you will NOT see 24VDC on the power output terminals - there is no step-up or regulation provided.
Ground Design
The 14-pin terminal block includes 5 screw terminals (2, 5, 8, 11, and 14) which are labeled as GND. These all short together, plus are connected directly to the GND (negative) terminal from the DC power supply. There is no isolation between the four 4 I/O circuits, nor between the I/O circuits and the power supply.
The AC/DC power supply included in the standard CPX4 has an isolated design, so there is no ground path between the DC power ground and the chassis or AC Physical Earth ground.
If you use an external excitation power supply, make sure you properly tie the floating DC ground of the CPX4 to the ground for the loop power.
Analog Inputs
The analog signals are read by the CPX4's XBee coordinator, which makes them behave much as the analog signals in the XBee AIO Adapter.
Analog Modes
- 0-10 volt Mode
- Full Scale Range: 0VDC to 10.25VDC
- Safe Input Range: -0.5VDC to 11VDC
- Input Impedance: 28200 ohms
- Note: Signals near zero volts lose accuracy, so avoid measure signals less than 0.2VDC
- Current Loop (4 to 20 mA) Mode
- Full Scale Range: 0mA to 23.5mA
- Maximum Safe Range: 40mA
- Input Impedance: 51.1 ohms
- Common Details
- Returns a 10-bit value in the range 0 to 1023
- Accuracy varies based on XBee technology. ZB, ZNet and 802.15.4 offer 0.2%, others are 0.4%
- In the iDigi/Dia framework, use driver 'devices.xbee.xbee.xbee_devices.xbee_local_aio:XBeeLocalAIO' with channel_mode set to 'TenV' and 'CurrentLoop' respectively.
Loop Diagrams
The internal excitation power from the CPX4 is only designed to operate standard 4-20mA loops. The numbers listed are the terminals on the 14-pin removable terminal block, with pin#1 being closest to the edge of the PCB and marked with a white silk-screen dot on the PCB:
If you require more power than 30mA, you must use an external power supply. The numbers listed are the terminals on the 14-pin removable terminal block:
Troubleshooting
You see wild readings like 60 or 284 mA
Check your wire connections. This has been observed when (as example) the plastic insulation of one wire is crimped into a screw terminal, so no contact is made. What happens is the CPX4H's input is artificially pulled high up near the max of 30vdc, yet no current is flowing. The self-calibration routine in the CPX4H gets confused by this and a large scaler value is applied.
Externally, you see no current flow even though your loop is correctly wired
Confirm Dia or your Python application is running. After power-up, the analog inputs may default to 0-10vdc, and so no current will flow until an application changes the settings to current loop.
