DC Load Device - MP71077x Driver

Electronic DC load control library using SCPI protocol over UDP.

Device Info

• Model: MP71077x series DC Electronic Load
• Interface: Ethernet (UDP Socket)
• Default Port: 3000
• Protocol: SCPI (Standard Commands for Programmable Instruments)

Installation

The MP71077x driver is part of the dcload_device package:

from dcload_device import MP71077x

Quick Start

from dcload_device import MP71077x

# Connect to load
load = MP71077x("192.168.1.80")

# Set CC mode current
load.set_ci_current(1.0)

# Enable input
load.input_on()

# Read back current setpoint
print(load.get_ci_current())

# Disable input
load.input_off()

API Reference

Initialization

load = MP71077x(ip, port=3000, timeout=2)

Parameters:

• ip (str): Device IP address
• port (int): UDP port (default: 3000)
• timeout (float): Socket timeout in seconds (default: 2)

Input Control

input_on()

Enable load input.

load.input_on()

input_off()

Disable load input.

load.input_off()

get_input_state() -> str

Query current input state.

state = load.get_input_state()  # "ON" or "OFF"

Voltage Settings (CV Mode)

set_cv_voltage(voltage: float)

Set constant-voltage setpoint.

load.set_cv_voltage(5.0)

get_cv_voltage() -> float

Read CV voltage setpoint.

set_upper_voltage_limit(limit: float)

Set upper voltage protection limit.

get_upper_voltage_limit() -> float

Read upper voltage limit.

set_lower_voltage_limit(limit: float)

Set lower voltage protection limit.

get_lower_voltage_limit() -> float

Read lower voltage limit.

Current Settings (CI Mode)

set_ci_current(current: float)

Set constant-current draw.

load.set_ci_current(2.0)  # draw 2A

get_ci_current() -> float

Read CI current setpoint.

set_upper_current_limit(limit: float)

Set upper current protection limit.

get_upper_current_limit() -> float

Read upper current limit.

set_lower_current_limit(limit: float)

Set lower current protection limit.

get_lower_current_limit() -> float

Read lower current limit.

Power Settings (CP Mode)

set_cp_power(power: float)

Set constant-power draw.

load.set_cp_power(10.0)  # draw 10W

get_cp_power() -> float

Read CP power setpoint.

set_upper_power_limit(limit: float) / get_upper_power_limit() -> float

Upper power protection limit.

set_lower_power_limit(limit: float) / get_lower_power_limit() -> float

Lower power protection limit.

Resistance Settings (CR Mode)

set_cr_resistance(resistance: float)

Set constant-resistance mode value.

load.set_cr_resistance(10.0)  # 10 Ohm

get_cr_resistance() -> float

Read CR resistance setpoint.

set_upper_resistance_limit(limit: float) / get_upper_resistance_limit() -> float

Upper resistance protection limit.

set_lower_resistance_limit(limit: float) / get_lower_resistance_limit() -> float

Lower resistance protection limit.

Low-Level IO

For advanced usage or custom SCPI commands:

write(cmd: str)

Send command to device (no response expected).

load.write(":INP 1")

query(cmd: str) -> str

Send command and retrieve response.

response = load.query(":CURR?")

REST API

Flask-based HTTP interface for remote access.

Starting the Server

cd dcload_device
python -m flask --app flask_app run --port 5000

Server runs on http://localhost:5000

API Endpoints

POST /input

Enable or disable load input.

Request:

{"state": true}

Response:

{"ok": true}

POST /set/voltage

Set CV voltage and/or voltage limits.

Request:

{"cv": 5.0, "upper": 30.0, "lower": 0.0}

POST /set/current

Set CI current and/or current limits.

Request:

{"ci": 2.0, "upper": 10.0, "lower": 0.0}

POST /set/power

Set CP power and/or power limits.

Request:

{"cp": 10.0, "upper": 200.0, "lower": 0.0}

POST /set/resistance

Set CR resistance and/or resistance limits.

Request:

{"cr": 10.0, "upper": 1000.0, "lower": 0.1}

GET /get/voltage

Read voltage setpoint and limits.

Response:

{"cv": 5.0, "upper": 30.0, "lower": 0.0}

GET /get/current

Read current setpoint and limits.

GET /get/power

Read power setpoint and limits.

GET /get/resistance

Read resistance setpoint and limits.

GET /input/state

Read input on/off state.

Response:

{"state": "ON"}

Common Patterns

CC Load Test

load = MP71077x("192.168.1.80")

load.set_ci_current(2.0)
load.set_upper_current_limit(5.0)
load.input_on()

Sweep Current

import time

for i in [0.5, 1.0, 1.5, 2.0, 2.5]:
    load.set_ci_current(i)
    time.sleep(1.0)

load.input_off()

Test with PSU

Verify PSU output and regulation under load:

from dcload_device import MP71077x
from psu_device import MP711001
import time

psu = MP711001("192.168.1.100")
load = MP71077x("192.168.1.80")

psu.set_voltage(1, 5.0)
psu.set_current(1, 3.0)
psu.output_on(1)

load.set_ci_current(2.0)
load.input_on()

time.sleep(1)

result = psu.measure(1)
print(f"Voltage under load: {result['voltage']}V")
print(f"Current drawn: {result['current']}A")

load.input_off()
psu.output_off(1)

Error Handling

The driver automatically reconnects on socket errors.

try:
    load.set_ci_current(2.0)
    load.input_on()
except Exception as e:
    print(f"Error: {e}")

Performance Notes

• Transport: UDP (connectionless); lower overhead than TCP
• Timing: 0.1-0.15s delay between commands for stability
• Reconnection: ~0.5s delay on error recovery

Troubleshooting

"Command response timeout"

• Check device IP address and that port 3000 is reachable
• Try increasing timeout parameter

Values not applying

• Confirm units match device expectations (V, A, W, OHM)
• Check that protection limits are set wide enough to allow the setpoint

See Also

• Main documentation: ../README.md
• PSU device: ../psu_device/README.md
• Multimeter device: ../multimeter_device/README.md