BECs & ESCs

[Paul Drone]

I am building my first hexacopter (Tarot T-960) and have purchased 6 HobbyWing Platinum Pro ESCs with BECs (thought at the time it was better to have BECs than not) to power 6 T-Motor MN4014s. My question is if I remove the red center pin from the servo cable on the ESC, will this have any negative effect on how they perform or would it be just like if I had purchased OPTO ESCs. These will be connected to a DJI A2 FC.

Thank you

Paul

 

[Mike]

Unless you have ESC's that can switch between BEC and OPTO, the short answer is no. Based on this, I don't think you do:

http://www.hobbywing.com/uploadfiles/sx/file/manual/HW-01-PL.pdf

The following is a very good read (scroll down to BEC vs OPTO)

http://aircraft-world.com/prod_datasheets/ac-esc.htm

The BEC just cuts down the voltage to your board/receiver so you can run everything off of your main battery without supplying too many volts. OPTO makes the connections optically to eliminate noise and give a cleaner signal between the ESC and the board/receiver, so to get power to the receiver with OPTO, you would need to either run power from your main battery to your own BEC, then to your receiver/board, or you need to run a separate battery altogether. Some say if you don't run a separate battery with OPTO, you won't get the noise eliminating benefits.

You'd need to read your board manual to get information on how to connect your ESC's with built in BEC to the board, but in a lot of cases, you'd remove all of the red wires to from the ESCs to the board, except for one to supply sufficient power. Also, your board will pass power to your receiver. Some boards have built in BEC's, so removing wires may not be necessary, but it varies. Also, if you have OPTO ESC's, you will normally leave the red wires all intact because in the case of OPTOs, the red wire typically draws power from the board/receiver.

In the end, it doesn't look like you'll be running OPTO with those ESCs, but it gets more interesting because the A2 has a separate power supply unit - so if you're using that, you will likely need to remove all of the red wires from the ESCs to the board so you don't damage the board. Check the manual/instructions to be safe though. I'm guessing it would give explicit instructions on how to connect them. Just make sure you remove the pins and wires cleanly in case you need to add them back for whatever reason.

 

[Paul Drone]

Thanks for the info. I think just to be safe, I'm going for return the BEC ESCs and exchange them for the OPTO equivalent. I'll save about $20 per ESC to boot.

 

[Mike]

Probably a good idea. OPTO is the better technology anyway if you're not considering the weight of having another battery. But if you're already running the power supply for the board, it doesn't matter.

 

[Paul Drone]

mm,

So I went ahead and returned the BEC ESCs and Helipal is sending out the OPTO replacements today. On a separate topic, I have been reading conflicting ideas about the length of the motor wires vs battery wires to the ESC. Some say shortest possible to the ESC from the motor and some say shortest to the battery from the ESC. They both can't be right. My thinking, with the motors I bought anyway (T-Motor 4014 400kv) come with very long (600+ mm) wires with gold bullet plugs. If they didn't think you needed long wires, why would they make them so long. So I mounted the motors in a way that has no exposed wires anywhere, and will place the ESCs on a CF board below the main deck and feed the motor wires out the bottom center of the main deck to the ESCs. See photos below.

In your opinion, will this be advantageous or cause issues.

 

[Mike]

Both scenarios have their downsides. To summarize - longer wires from the battery to ESC can damage the ESC over time. Longer motor wires may see some increased radio interference. The good thing is that you can solve the interference issue for the most part on long motor wires by twisting them (the three wires). If using longer battery to ESC wires, you'd want to add some capacitors:

http://www.matthias-schulze-elektronik.de/guide/gfutc-de.pdf

So ultimately, longer motor wires is the better choice.

That's a beautiful build so far. Very good quality frame based on those close ups.

 

[Paul Drone]

I did read that twisting the wires helps reduce interference so I did twist them and zip tied them every 6 inches or so before inserting down the CF arms. I used a vacuum to "suck" a lead string through the arm and then pulled the twisted wire harness back down and out into the main frame of the T-960. The folding arms are a little harder as there is only a small opening on the side of the tube arm, whereas the fixed arms are simply open on the ends.

 

[Mike]

You should be good then. Honestly, not twisting them likely would not have caused any noticeable issues, but it's always better to be on the safe side. Good luck!