EDF/UNO R2 help needed.

Hi @pilot-major,

   I am sorry, but I am not experienced with EDF controllers, so I cannot offer any direct detailed advice, but hopefully others will be forthcoming.

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However, I am somewhat confused as to the situation and difficulty you describe. My oversimplified impression, is that each EDF controller will have a fairly simple (from an electrical viewpoint) pulse modulation interface, based on driving servos, that is normally connected to a radio control system.

If my impression that the EDF controller interface is similar to a 'conventional' servo used in radio control applications, is essentially correct, then the electrical connection of each controller, will be similar to that of connecting a servo, which is a topic that is discussed widely on the web, including by Bill (@dronebot-workshop) who kindly provides this forum. 

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The only manual I have found for ZTW Beatles controller (a single sheet style PDF at
https://d3if9wubzr0anm.cloudfront.net/manuals/ZTW3050211-1.pdf), appears to show 4 'groups' of connections:

1. Throttle Signal wire ... three wires in a group, similar to servo discussed below
2. Reverse signal wire
3. Battery connection ... pair of wires, probably red and black
4. Group of three wires to connect to a motor

Unfortunately, I can't see any further description, so I'll have to make some guesses. Apologies if any are wrong.

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Starting with consideration of 1.  'Throttle Signal wire', I am guessing this is the same as a 'conventional' radio control servo.

https://dronebotworkshop.com/servo-motors-with-arduino/ discusses connecting a single servo, including diagrams, such as:

  (click on picture to enlarge)

which shows, the control connection is a single wire from an Arduino GPIO output (plus earth return) to the servo.

The Arduino pin (number) must be chosen to meet the requirements of the task, which in turn is dependent upon the Arduino software that is controlling the output 'messages' (using PWM encoding) sent to the servo.

In this particular article, the code sample accompanying the wiring includes:

void setup() {
myservo.attach(9); // attaches the servo on pin 9 to the servo object
}

which defines the GPIO pin used to drive the servo, namely pin 9. Examination of the wiring diagram above, shows the orange wire connects the servo control input to GPIO pin 9 on the Arduino.

The Arduino could control more servos, similarly, with a separate suitable GPIO pin being chosen for each servo, and the software program being extended to match.

I am guessing the Arduino power and ground, would be connected to the other two wires in the group to the EDF controller. Note that in this servo example, the power is supplied by an external source, with 0V linked to Arduino 0V, because the power is driving the servo motor. With the EDF controllers, the power source for the motor is a separate connection to the battery, and I am guessing the power in this group of wires only supplies some electronics within the EDF controller, which can probably be supplied from the +5V output from the Arduino.

Unfortunately, I haven't found any specification, so I can't be sure of the above suggestion. Perhaps you can find something, or try emailing ZTW, to check ? The +5V output from the Arduino only has a limited current capability, so I am concerned that the power draw from 3 ZTMs might be excessive. I am also guessing that 5V is a suitable voltage. Please try to check these aspects. 

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Of course, practical experience, which I do not have, may show I have misunderstood or missed some important issues, but my impression is that the electrical wiring for 3 or 6 servos (and hence 3 or 6 EDF controllers) is actually fairly simple, essentially being one control wire, plus low current power and ground, per EDF controller.

Note, the EDF controller will be controlling much higher currents than this servo example, so you will need to be careful with the higher power wires between the battery and the controller. Check out some of the other articles that Bill has posted on controlling higher power motors and servos to appreciate this issue.

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The three motor wires from the controller to its respective motor appears to be obvious, ensuring you use wire of sufficient thickness, if they need to be extended.

Note, as per the ZTW sheet referenced above, if the motor spins in the wrong direction, swap two of the wire connections.

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2. Reverse Signal Wire

I haven't found any technical specification, so this is a wild-ish guess. 
As a servo drive control line can only send a message that 'means' 0% to 100% of 'something' ... e.g motor speed. It cannot send 'reverse direction'.

Hence, I guess this line will provide this capability. I would also guess that this would be suitable for connecting to a GPIO pin, but I don't know if it would be 'short to ground' for reverse, or drive to 3.3/5V or reverse, or possibly something I haven't thought of. 

If you only need the motor to run in one direction, then I would guess you could ignore this wire ... just make sure it can't accidentally make contact with another circuit. If you need it, then preferably find some further information, or at your own risk, try connecting to ground. If, that fails, try connecting to 3-5V source.

Assuming, you can determine the required drive type, and show it is compatible with 'logic' level control, then it should be possible to allocate an Arduino GPIO pin to the task, and programme it suitably.

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All of the above is a kind of speculative road map of how I would approach your problem, if I were faced with it. I would start with a single Arduino, controller and motor. Perform a number of experiments to get familiar with the system. Only when I think I completely understand how to power and control a single motor properly, would I even contemplate the issues of scaling it up to 6 motors, etc.

The code sample referred to above can easily be adapted to drive a single motor, demonstrating the ability to set the speed to any desired value. Extending it to drive a second pin, for reverse, would also be trivial.

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Simplistically, extending it to 3 or 6 motors, might be basically a copy and paste operation, taking care to match the GPIO pin number to the physical connection.

I note that the code includes the comment "// twelve servo objects can be created on most boards", suggesting that all GPIO pins can be utilised in this way, but be aware that not all GPIO pins, on all board types, are created equal, so sometimes library functions, like Servo in this example, may be limited to certain pins. Hopefully, this will not be a problem, but this can be checked out as part of the one motor testing.

However, this ignores any need for synchronising and coordinating the drive to 6 motors at the same time. This will largely affect the software design, after you have connected all motors, and checked they can be individually controlled by the Arduinos. It may include some means of linking the two Arduinos to ensure they are coordinated.

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Sorry this is a sermon, not a simple answer to your request, but I hope it gives you a place to start. Feel free to ask further questions, but I don't think I can help on a webchat.

Please keep safety in mind ... your motors will have a considerable amount of mechanical and electrical power that they could misuse, if not treated with respect and care. If you haven't used servos before, I suggest you take a short break, and repeat some of the experiments described by Bill.

In addition, I emphasise that much of the above includes guesswork ... there maybe (probably will be!) errors ... for which I take no responsibility. 

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Good luck ... I wish you well with your project.

Best wishes, Dave