Author: Gregor

Although the servo output of an RC receiver provides all the information required to control an L298N or IBT-4 motor driver, the signal must be appropriately decoded and re-encoded, since the control logic of a motor driver is fundamentally different from that of an RC servo.

This task can be performed by the RCRX2Bridge II module.. This is a single-chip solution that processes one channel and uses it to control one motor via an L296 bridge or an IBT-4 motor driver. The device expects a standard PWM signal for analog servos, with a pulse width ranging from 1,000 µs to 2,000 µs, a neutral position at 1,500 µs, and a repetition period of approximately 20 ms.

With the new version of the module, the width of the range in which the motor is not driven — the hysteresis — can now be adjusted via a trimmer on the circuit board (see image). This now also allows support for simpler remote control receivers whose pulse widths fluctuate by more than 5 µs in the neutral position (up to a maximum of 100 µs with the trimmer turned fully to the left).

The circuit is very simple, and the breakout board already comes populated with all SMD components, so only the pin headers still need to be soldered. The assembly is both electrically and mechanically backward compatible with the first version of the RCRX2Bridge.

RCRX2Bridge II continues to support the two common but different control schemes used by L298N bridges: models with 2/4-phase control and models with two logic inputs and one speed input, as well as the IBT-4 motor driver.

Control of bridges with two inputs

The RCRX2Bridge II module is connected to the receiver on the input side, as shown in the featured image. The input pins of the motor driver IN1 and IN2 are connected to the output pins of the breakout board as shown in the featured image. If a second motor is to be controlled, then a second RCRX2Bridge II -module is required..

Control of bridges with three inputs

 

For this application, the RCRX2Bridge II module is configured for the changed logic using a solder bridge at “MODE” and then also connected to the receiver on the input side, as shown in the featured image.

The input pins of the motor driver ENA, IN1, and IN2 are connected to the output pins of the breakout board as shown in the image to the right. If a second motor is to be controlled, then a second RCRX2Bridge II -module is required.

Controlling the IBT-4 Motor Driver

The IBT-4 motor driver is controlled via the two inputs IN1 and IN2. The required signals are identical to those used for the bridge with two inputs, so no solder bridge or any other modification is required (see above).

The required connections are shown in the following diagram:

The kit for the breakout board with the RCRX2Bridge II controller is available in the store.

Although the servo output of an RC receiver provides all the information required to control an L298N motor driver, the signal must be evaluated and recoded in a suitable manner, as the control logic of the motor driver is fundamentally different to that of an RC servo.

This task can be performed by the RCRX2Bridge module. This is a single-chip solution that evaluates one channel at a time and thus controls one motor of the L296 bridge. The circuit is very simple, and the module is quick to assemble with the breakout board.

 

RCRX2Bridge supports the two common, but different control modes of L298N bridges: Models with 2/4 phases and models with two logic inputs and one speed input.

Control of bridges with two inputs

 

The RCRX2Bridge module is connected to the receiver on the input side, as shown in the picture. The input pins of the motor driver IN1 and IN2 are connected to the output pins of the breakout board as shown in the picture. If a second motor is to be controlled, a second RCRX2Bridge module is required.

Control of bridges with three inputs

 

For this application, the RCRX2Bridge module is configured for the changed logic using a solder bridge at “MODE” and then also connected to the receiver on the input side in this case, as shown in the article image.

The input pins of the motor driver ENA, IN1 and IN2 are connected to the output pins of the breakout board as shown in the picture. If a second motor is to be controlled, a second RCRX2Bridge module is also required here.

 

The kit for the breakout board with the RCRX2Bridge controller is available in the store.

 

Overview

In the field of robotics, it is often necessary to control several servos by wire, e.g. when realizing a robot arm or an underwater ROV. In this case, operation with a gamepad or joystick is ideal because the large number of axes / degrees of freedom enables efficient control of many channels.

This blog describes the setup for controlling eight servos by wire using the free Windows APP JoystickRC.

The mapping of the axes and switches to the servo channels is done flexibly in the software. The actual pulse generation for the servos is performed by a PiKoder Serial Servo Controller (PiKoder/SSCng), which is connected to the PC via its USB interface.

Setup

The setup is ideally carried out with the aid of a PiKoder/SSCng –development board and with a standard USB cable. The PiKoder is supplied with power via the USB port. As the USB interface cannot supply enough power to operate the servos, they must be supplied with an independent power source via the terminal strip. In order to prevent balancing currents that could damage the PC, the jumper must not be plugged into the PiKoder circuit board under any circumstances. More detailed information can be found in the PiKoder User Manual.

Software

The JoystickRC program is available free of charge from the Microsoft Store. You can find more instructions on how to use the program on the program’s website.