Introduction

In outdoor industrial IoT scenarios, wireless data radios face extremely harsh survival challenges: torrential rain soaking, scorching sun exposure, freezing cold, and dust and sand intrusion. Ordinary data radios often fail quickly in such environments, leading to communication interruptions and data loss, causing significant losses to engineering projects.

However, the traditional solution of "adding a waterproof enclosure" not only increases costs but also affects antenna signal quality and installation convenience. For outdoor applications such as agricultural irrigation, photovoltaic monitoring, and industrial meter reading, the market urgently needs a waterproof wireless data radio that can be directly exposed to harsh environments while still operating stably.

The E91-DTU(xxxSL30) series and E91-DTU(400SL37) launched by Chengdu EBYTE Electronic Technology Co., Ltd. are purpose-built to address this core pain point. They are EBYTE's next-generation LoRa waterproof wireless data radios, featuring IP67 waterproof rating, industrial-grade wide temperature range, and high-power long-distance communication — allowing wireless communication to fear no weather

Product Overview 

The E91-DTU series is EBYTE's next-generation LoRa waterproof wireless data radio, developed based on Semtech high-performance RF chips. They feature an IP67 waterproof plastic housing with silicone ring sealing and internal potting, capable of withstanding short-term submersion and long-term rain exposure.

The E91 series currently includes the following models:

Core Selling Points:

• IP67 Waterproof and Dustproof: Can be directly submerged in 1 meter of water for 30 minutes — no additional waterproof enclosure required.

• Industrial-Grade Wide Temperature: -40°C to +85°C operating temperature, adaptable to environments from the Arctic to the desert.

• Wide Voltage Input: Supports 8~28V DC (400SL37 supports 10~28V), compatible with solar power, batteries, and various other power supply methods.

• RS485 Communication Interface: Uses M12 waterproof aviation connector, simple and reliable.

 Features and Model Comparison

Common Features of All Three Models

• IP67 Waterproof Rating: Triple waterproof protection — flame-retardant plastic waterproof housing + silicone ring sealing + internal potting treatment.

• High Power Transmission: 400SL30 and 900SL30 at 30dBm (1W); 400SL37 at 37dBm (5W).

• Wide Voltage Power Supply: 8~28V DC wide voltage input (400SL37: 10~28V), compatible with solar power, batteries, switching power supplies, and other scenarios.

• Dual Command Systems: Supports both HEX commands and AT commands for configuration, flexibly adapting to different user preferences.

• Multiple Operating Modes: Supports Transmission Mode (transparent transmission), WOR Mode (air wake-up), Configuration Mode, and Sleep Mode.

• Relay Networking: Supports multi-level relay for ultra-long distance communication.

• Communication Encryption: Supports user-defined communication keys that cannot be read, ensuring data security.

• LBT Function (Listen Before Talk): Monitors channel ambient noise before transmission, improving communication success rate in harsh environments.

• RSSI Signal Strength Indication: Used for evaluating signal quality and optimizing antenna installation.

• Wireless Configuration: Supports sending command data packets wirelessly for remote parameter configuration or reading.

• Modbus Protocol Transmission: Supports Modbus RTU protocol transparent transmission.

Comparison of the Three Models

Quick Selection Guide

 Technical Specifications

Core RF Parameters Summary

Electrical Parameters Summary

Factory Default Parameters

Application Scenarios — Scenarios That Cannot Do Without the E91-DTU

Scenario 1: Smart Agricultural Irrigation and Environmental Monitoring

• Requirements: Sensors and control valves are distributed across vast farmland. Heavy rain and direct spray from irrigation guns are commonplace — equipment must be fully waterproof.

• Solution: The IP67 waterproof and wide temperature (-40~85°C) characteristics of the E91-DTU(400SL30) allow it to be installed on cement posts in the field. The 8km communication range covers large farmland areas without the need for relays.

Scenario 2: Photovoltaic Power Station Monitoring

• Requirements: Solar panel arrays are exposed to direct sunlight. Summer surface temperatures can reach 70°C, while winter temperatures may drop to -30°C. Equipment must withstand extreme temperature differences and have rain and dust resistance.

• Solution: The wide temperature range of the E91-DTU(400SL30) perfectly adapts to the photovoltaic station environment. The wide voltage input (8~28V) is compatible with solar panel + battery power supply configurations.

Scenario 3: Water Source and Pump Station Monitoring

• Requirements: Equipment is installed in humid well rooms, riverbanks, and reservoir sides, with extremely high humidity and continuous water vapor erosion risk.

• Solution: The IP67 potting waterproof process ensures that water vapor cannot enter the internal circuitry. The 5W version (400SL37) can cover ultra-long distances of 25km from the water source to the main control room.

Scenario 4: Building Automation and Heating Pipe Network Monitoring

• Requirements: Sensors are deployed in underground pipe galleries and damp pipe wells — harsh environments with inconvenient maintenance.

• Solution: The E91-DTU(900SL30) is suitable for European and American markets. Its compact size (90×53×42mm) makes it easy to install in narrow pipe wells.

Scenario 5: Urban Waterlogging Water Level Monitoring

• Requirements: Equipment needs to be installed in low-lying areas and near drainage outlets, and may be briefly submerged by rainwater.

• Solution: The IP67 protection rating allows the device to still communicate normally after short-term underwater submersion — a perfectly matched solution for waterlogging monitoring scenarios.

EBYTE Core Advantages

IP67 Waterproof + Industrial Wide Temperature

This is the most important differentiating advantage of the E91 series. Unlike ordinary DTUs (which can only be installed in electrical control cabinets), the E91 can be directly exposed to outdoor environments without the need for an external waterproof enclosure, significantly reducing installation complexity and cost.

M12 Waterproof Aviation Connector

The wiring port uses a 5-pin M12 waterproof aviation plug, ensuring that the connection point is also waterproof — providing seamless protection with no weak points.

Multiple Operating Modes and Dual Command Systems

Supports four operating modes: Transmission Mode, WOR Mode, Configuration Mode, and Sleep Mode. Supports both HEX and AT dual command systems, allowing users to flexibly choose based on their development preferences.

Relay Networking and Communication Encryption

Supports multi-level relay networking. Multiple independent networks can operate in the same area. The communication key function ensures data transmission security.

Complete Product Portfolio

Three models — 400SL30 (1W/8km), 900SL30 (1W/8km/international band), 400SL37 (5W/25km) — covering a range of distance requirements from 8km to 25km.

Rich Supporting Documentation

Provides product specifications, user manual, AT command list, register configuration guide, antenna recommendations, FAQ, and a full set of technical documentation.

Frequently Asked Questions (FAQ)

Q1: The actual transmission distance is far lower than the rated 8km or 25km. What should I do?

A: The rated distances (8km/25km) are tested under ideal conditions (clear open area, antenna height 2.5m, air data rate 2.4kbps, high-gain antenna). Attenuation factors in practical applications include:

• Obstacles: Trees, buildings, hills, etc., significantly attenuate signals. The 900MHz band has weaker diffraction capability.

• Antenna quality: Use high-quality high-gain antennas (5dBi or higher recommended). Ensure there is no metal obstruction around the antenna.

• Supply voltage: Ensure the supply voltage is within the recommended range. Low voltage reduces transmission power.

• Air data rate: Lower rates (e.g., 2.4kbps) provide longer range.

• Antenna height: Increasing the antenna installation height effectively extends communication distance.

Q2: How do I wire the device correctly? What is the 485_A and 485_B pinout?

A: The E91-DTU uses an M12 5-pin aviation connector. The wire color definitions are as follows:

Note: If communication issues occur when multiple devices are connected but work fine with a single device, connect a 120Ω termination resistor in parallel between the 485_A and 485_B terminals.

Q3: Multiple devices have communication issues. How do I troubleshoot?

A: Follow these steps to troubleshoot:

1. Check wiring: Confirm whether the 485_A and 485_B wires are reversed.

2. Check parameters: Confirm that the air data rate, network address (NETID), channel, and communication key are consistent across all devices.

3. Check address: The module addresses of communicating parties should match. For broadcast, set to FFFF (the module will not perform address filtering in this case).

4. Termination resistor: As mentioned above, a 120Ω termination resistor should be connected in parallel on the 485 bus.

5. Power quality: Check if the power supply ripple is too large. A regulated power supply is recommended.

Q4: How do I enter configuration mode?

A: The E91-DTU(xxxSL30) series uses software mode switching via AT commands:

• AT+MODE=0: Transmission Mode (transparent transmission, factory default)

• AT+MODE=1: WOR Mode (supports air wake-up)

• AT+MODE=2: Configuration Mode (access registers via serial port)

• AT+MODE=3: Deep Sleep Mode

Q5: What are the main differences between E91-400SL30 and E91-400SL37?

A: The core differences are in transmission power, supply voltage, and reference range:

The 400SL30 is suitable for most scenarios. The 400SL37 is designed for extreme scenarios requiring ultra-long distance coverage.

Q6: How do I configure the channel?

A: Use the AT command:

• 400MHz band: AT+CHANNEL=<ch> (ch range: 0~83, actual frequency = 410.125 + ch × 1MHz)

• 900MHz band: AT+CHANNEL=<ch> (ch range: 0~80, actual frequency = 850.125 + ch × 1MHz)

Q7: What air data rates does the module support? How do I choose?

A: Supports multiple adjustable rates from 2.4K to 62.5Kbps (400SL37 supports 0.3K to 62.5Kbps). Set via the AT+RATE=<rate> command.

Selection principle: Lower air data rate → longer communication distance; higher air data rate → lower latency. For distance-priority scenarios, 2.4Kbps is recommended. For throughput-priority scenarios, adjust to 62.5Kbps.

Q8: What is the WOR (Wake-on-Radio) mode? How does it save power?

A: WOR mode allows the receiving module to periodically wake up, listen for a preamble signal, and return to sleep if no signal is detected. This significantly reduces average power consumption for battery-powered receiving nodes. Use AT+MODE=1 to enable WOR mode. The wake-up interval can be configured to balance power saving and response latency.

Q9: How does the LBT (Listen Before Talk) function work?

A: When LBT is enabled, the module monitors the channel's ambient noise level before each transmission. If the channel is occupied (noise exceeds the threshold), the module delays transmission and retries after a random backoff period. This is particularly useful in environments with multiple radio systems operating nearby, reducing packet collision rates.

Q10: Can I configure the module wirelessly without physical access?

A: Yes. The E91-DTU series supports wireless configuration. You can send command data packets wirelessly to remotely configure or read parameters. This is extremely useful for devices installed in hard-to-reach locations such as high poles, underground pipe wells, or remote field sites.

Q11: Does the module support Modbus RTU protocol?

A: Yes. The E91-DTU series supports Modbus RTU protocol transparent transmission. The RS485 interface allows direct connection to Modbus RTU devices such as PLCs, sensors, and actuators. The module transparently transmits Modbus frames over the air, making it compatible with existing Modbus-based SCADA systems.

Q12: What antennas are recommended for this series?

A: The module uses an SMA-K (female pin, male hole) connector with 50Ω impedance. Recommended antennas:

• For 400SL30/400SL37 (410-493MHz): Use a 433MHz or 470MHz antenna. A quarter-wave whip antenna (approximately 17cm for 433MHz) or a high-gain fiberglass antenna (5-8dBi) for maximum range.

• For 900SL30 (850-930MHz): Use an 868MHz or 915MHz antenna. A quarter-wave whip antenna (approximately 8cm for 868MHz) or a high-gain directional antenna.

Important: Always connect an antenna before transmitting. Never transmit without an antenna — doing so can damage the power amplifier.

Q13: What is the default communication key? How do I set a custom key?

A: The default communication key is typically all zeros (no encryption). To set a custom key, use the AT command: AT+KEY=<key_value>. The key is stored in the module's non-volatile memory and cannot be read back for security reasons. All devices in the same network must use the same key to communicate.

Q14: Can the E91-DTU series be used for satellite communication?

A: No. The E91-DTU series is designed for terrestrial LoRa communication in the Sub-GHz ISM bands (410-493MHz or 850-930MHz). It does not support satellite frequency bands. For satellite communication needs, please consult EBYTE for appropriate product recommendations.

Q15: What certifications do these products have?

A: EBYTE products comply with RoHS and REACH standards. The E91-DTU series uses lead-free production processes and undergoes rigorous testing. For specific regional certifications (FCC, CE, SRRC, etc.), please contact EBYTE directly for the latest certification status for each model.

In summary, the E91-DTU(400SL30/900SL30/400SL37) series is EBYTE's IP67 waterproof LoRa data radio family, tailor-made for harsh outdoor environments. With the core selling point of "waterproof design that requires no protective enclosure", combined with industrial-grade features such as wide temperature range, wide voltage input, and high power output, they precisely address the core pain point of "harsh outdoor wireless communication environments" in fields such as agriculture, photovoltaics, water utilities, and industrial parks.