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.

In the previous article we already presented the possibility to control up to eight servos via a USB interface using a joystick or gamepad, a PC and a PiKoder/SSC. Here is now described how a wireless model remote control can be realized with a PiKoder – receiver, the PiKoder/SSC RX. Bluetooth for command transmission.

Setup

First, the PiKoder/SSC RX must be connected to the PC at the operating system level. For this purpose, you first search for new Bluetooth devices in the device control.

After a short time, the Bluetooth module of the receiver should be offered. The PIN is “1234”.

With the selection “Connect” the coupling (pairing) takes place on system level.

As the following view from the device manager shows, the coupling of the system also establishes two virtual serial interfaces, which we access later in the program for establishing a connection.

This completes the setup and the JoystickRC program can now be started as described in the previous post.

This tester reproduces the output of the receiver 191/S – a relay with a switching contact – with a corresponding button. Thus, the function of the rowing machine, which depends on the control panel used, can then be tested.

In my case, the control panel 1 is inserted; the following switch rhythm is realized according to the user manual:

• Transmitter key pressed: Rudder left as long as button remains pressed
• Press the transmitter button briefly (approx. 0.4 seconds), release briefly (approx. 0.4 seconds) and hold down: Rudder on the right, as long as the button is pressed the second time.
• After letting go of the transmitter button, the rudder always goes neutral by itself.

In the setup presented here, of course, the transmitter button corresponds to the button.

The tester can be easily mounted on a laboratory circuit board and the wiring effort is minimal. As can be seen in the picture, I realized the required 7-pin plug for connection with the rowing machine by inserting soldering nails into a 7-pin tube socket.

The servo tester presented here is equipped with a PIC controller to provide for very accurate pulse generation (pulse width: 1 ms – 2 ms) especially in comparison with a simpler construction with RC links. For this purpose, the internal oscillator is used, which is specified in the selected range of the supply voltage with an accuracy of 1 %.

Furthermore, the servo tester is characterized by the fact that, in contrast to other simpler digital devices, the supply voltage range is specified form 4.8 V – 6 V. With this, the servo tester can also be connected to the BEC connection of a speed controller. The polarity of the pulse for servo control can be adjusted by hardware (jumper setting).

In addition, the Servo Tester enables the use of servos for other applications, such as for rotating and panning surveillance cameras.

Circuit

The circuit is based on the PIC12F675, which controls the servo tester. The supply voltage of the controller is lowered to 3.3 V by a corresponding controller; this ensures the highest accuracy of the internal oscillator on the one hand and the large supply voltage range of the tester on the other hand.

However, this approach requires a driver transistor Q1, which performs the level adjustment to control the servo. The supply voltage of the servo is directly looped through, so that servos or motor controllers can be tested either with the already existing battery / BEC supply by the speed controller or by means of an additional power supply (in this configuration it must be ensured that no power is provided via the servo plug).

The jumper JP3 determines the polarity of the control pulse for the servo. Please note that the LED is a bi-color LED.

Operation

The operation is simple and intuitive. The servo tester has two different operating modes: the manual mode, in which the servo is controlled by a rotary knob P1 and the neutral position can be adjusted and the exercise mode, in which the servo is continuosly moving between the end points. The change between the two operating modes is carried out by pressing the button S1. The LED will indicate the active mode of the servo tester.

After switching on, the device is in manual mode and the servo position is adjusted by rotation of the potentiometer P1. In the pulse area outside the window of 1.45 ms and 1.55 ms, the LED lights up in green. To move the servo to the neutral position, the color of the LED within the window of 1.45 – 1.55 ms changes to yellow or both colors of the LED light up and when the neutral position of 1.5 ms is reached, red is finally displayed; no button has to be pressed and both hands are free to perform adjustment work if necessary.

The Exercise Mode offers two speeds to choose from. The LED flashes red in this mode and shows which speed was selected via its flashing frequency (0.25 s corresponding to 2 x flashing/second or 15 s (correspondingly once 2 s on, then 2 s off) from final rash to final rash). The speed is switched by turning the potentiometer: if a pulse length greater than 1.5 ms is set, then the Exercise Mode is selected at high speed, otherwise the servo is controlled slowly.

Software Download

The firmware for the servo tester (Release 1.0) is freeware, which can be used without restrictions for private, non-commercial purposes according to the underlying End User License Agreement (EULA).

Servotester kit and components

In my shop you will find a complete kit for the tester.

Soll WLAN als Übertragungsweg genutzt werden, dann kann ein solcher Kanal senderseitig mit einem ESP8266-01 Modul realisiert werden; als Empfänger kommt ein PiKoder/SSC wRX zum Einsatz.

In diesem Fall werden neben den Basiskomponenten wie Steuerknüppeln, Schalter, etc., die zum Aufbau des arduinodtx-basierten Fernsteuersenders erforderlich sind, ein Logic Level Umsetzer von 5 auf 3,3 Volt, zwei Jumper zur Umschaltung der seriellen Kommunikationsschnittstelle (UART-Multiplexer) und ein ESP8266-01 Modul benötigt wie im Beitragsbild dargestellt. Die Verdrahtung entnehmen Sie dem folgenden Schaltbild (die Signale mit gleicher Bezeichnung müssen verbunden werden, Signale in blauer Schrift sind mit den entsprechenden Arduino-Signalen zu verbinden):

Der Aufbau ist relativ einfach und sollte problemlos auf einem Prototyp-Board erfolgen können.  

Im nächsten Schritt ist der ESP8266-01 als Access Point mit seriellem Ausgang zu programmieren – die Beschreibung hierzu finden Sie im Blog ESP8266-01 Sketch für den PiKoder/SSC wRX. Wollen Sie den ESP8266-01 im “eingesetzten Zustand” programmieren, dann müssen Sie die dargestellte Schaltung um einen Programmierteil erweitern:

Bitte beachten Sie auch die Jumperstellung für D0/D1. Zusätzlich sollte bei jeder direkten Kommunikation mit dem ESP8266-01 der Arduino “stillgelegt” werden (RESET Leitung auf GND legen), so dass die Datenübertragung nicht gestört wird.

Mit dem erfolgreichen Abschluss der Programmierung des ESP8266-01, dem Umstecken der Jumper, Aufwecken des Arduino und einem Reboot ist die Modellfernsteuerung betriebsbereit.