EX-MotorShield8874

ATTENTION UK, EU, Australia, and New Zealand users: You may be able to save time and shipping costs by ordering from the suppliers listed here:

• EU - MRW Electronics in Austria
• UK - Chesterfield
• AU/NZ - Millennium Engineering
• Canada - Narrow Gauge Model Railway Supply Canada
• USA/Canada alternate source - Smart Hobby

TARIFF NOTE: The tariff tax has increased our prices by 60%. We will try to not raise prices, but the uncertainty of this tax changing on a whim makes it difficult to plan. We will keep you posted if there are any changes.

IMPORTANT OLED NOTE: OLED Header does not include the actual display, it is just a connector for an optional display. Also, if you stack a board on top of the 8874 (like a WiFi shield) it will block the OLED header. There are several ways to connect I2C devices to the EX-MotorShield8874. There is a Qwiic/Stemma QT/JST (all the same thing) side facing connector, an 8 pin male header that can connect 2 devices, and the optional OLED header. The OLED header is just a convenience for people who want to stick a display on top without having to use jumpers on command stations where a 8874 can be the top board. CRITICAL: make sure optional the display you purchase has pins that are in the correct order. For some crazy reason, most .96" OLEDs are wired with the GND pin first and will work, while most (not all) 1.3" OLEDs usually have the Vcc pin first which will release smoke! Make sure you purchase the OLED with the pins in the correct order.

Overview

The EX-Motorshield8874 is pin compatible with the original Arduino Motor Shield Rev3 but provides significantly improved electrical performance for driving higher loads, and improved usability.

• Rated for 5 Amps of continuous output current
• 2 outputs (Main and Programming Track or 2 Mains)
• Single power supply input powers the shield, the Arduino, and the track (motor output)!
• 5V and 3.3V compatible
• Virtually no voltage drop, even at high currents
• I2C header for connecting accessories
• Reverse polarity protection
• Fault detection in addition to overcurrent reporting for extra safety
• Alternative power in and out solder pads for different connector types
• Stackable (Support multiple Power Districts)

The EX-Motorshield8874 is based on two DRV8874 H-bridge motor drivers with integrated current sensing from Texas Instruments (TI). It is used to drive inductive loads like relays, solenoids, DC and stepping motors, as well as provide the DCC signal and power to the model railroad tracks.

Powering of Arduino boards is possible due to the on board DC/DC buck converter, supporting a wide input supply range from 9 to 30V. The reverse polarity protection prevents damage to the circuit and its components in case the power supply is accidentally connected backwards.

The board's 5V and 3V3 friendly design makes it suitable for a broad range of Arduino compatible platforms, with an override that compensates for designs with incomplete support (such as an incorrect IORef voltage).

This Shield features a status LED for supply, which provides a visual indication of the power supply status.

Why did we make it?

EX-Motorshield8874 is specifically designed for use with DCC-EX Command Station for controlling model railroads, but can also be used as generally better replacement for Arduino Motor Shield R3 in any device that needs to control a motor. We needed higher current capacity to power more motors/trains and have little to no voltage drop due to advanced MOSFET driver technology.

Where can I find out more?

For more detailed information follow the link to the EX-Motorshield8874 on Github. It also includes the schematic and the KiCad project files.

NOTE: US boards can be blue or green with included, matching pluggable screw terminal connectors and a barrel power input connector. Other 2.54mm connectors are available upon request to replace any of these, or you can purchase the board as a kit and solder on your own connectors.

Reference

• Schematic
• DRV8874 Datasheet
• Documentation