Separating power supply

[Eric Hartley]

Hi
Whilst I have been used to electric flight for some years in both planes and quads I know very little about helicopters. At present I power my Align 450 plus with a 3s Lipo which I plug in via the ESC like any other electric model. I am presently converting an HK450 to fbl.The APM 2.6 board I have for the stabilisation system requires power for the Rx via a power module which is straight forward however the motor and servos require a separate power supply.As the receiver uses very little power would it be ok to rig a sort of Y connector from the Lipo as due to weight and space I don't think it practical to use two batteries.

[Allan Bennett]

I was hoping someone with APM 2.6 experience would chip in on this, but since they haven't, here's my take on it:-

The APM "power module" is essentially the same as a stand-alone BEC which we might use for receiver and servos. It supplies 5.37v at up to 2.25A to the APM. Note that, according to this page, it can also supply power to the receiver, but not the servos -- presumably due to its limited current capability.

Then reading on, we see that the "output" side of the APM uses a separate +ve line from the "input" side, which can be connected to that of the "input" side by a jumper, or can be powered separately with another BEC to supply power to the servos. Alternatively, and I quote from my link, "But if a sufficiently large external BEC is used it can supply power for both via the OUTPUT connector". Seems to me that's the simplest way to do it -- put the jumper in, and then use an adequate BEC to supply power to everything.

Maybe you've figured that part of it out already. So, in answer to your question, yes you can simply Y-lead the input wires of the APM power module and the input wires of your ESC/BEC so that they both take their supply from your 3S LiPo.

[Eric Hartley]

Hi Allan

Thanks for the info.

I am proposing to use a Turnigy plush 40A esc with BEC 3A/5V do you think this will be ok instead of using a separate BEC. Incidentally I have a 5A UBEC still in its wrapper - would this be a better spec than the esc? Ideally I would prefer to use the esc as I have never used a separate UBEC before.

[Allan Bennett]

I would definitely NOT use the BEC in the ESC, for it's a linear one, and it's rated for less amps than your UBEC. Your UBEC should be a switching BEC, which can handle higher input voltage and higher current without generating as much heat as a linear one does. Check the make and model on the internet to make sure it's described as "switching".

Using a stand-alone BEC alongside the ESC is quite simple: You connect its incoming power wires to the ESC's power wires, usually at the plug that goes to the battery. Then you disable the ESC's BEC by pulling the middle pin, with the red wire, out of its plug that goes to the receiver. Use a pointy knife blade to pry up the little tab that holds the pin in the plastic plug, then pull the red wire out. Tape it back on itself so it can't accidentally touch anything, and you can then reinsert it if you want to use it in the future. Then the ESC goes to the throttle channel in the receiver, as normal, so it can get the throttle signal, and the BEC's output goes to any spare channel in your receiver. It can be Y-leaded into the throttle channel with the ESC if you don't have any spare slots.

Just out of interest, what made you choose the APM board instead of a "conventional" flybarless controller such as the MicroBeast? Will it be able to hold position, fly itself, and return to base with that board?

[Eric Hartley]

Hi

The UBEC I have is the Hobbywing(from Giant Shark) 5A MAX 7.5A which apparently is the switching type and therefore if I leave the 'jumper' connection in place on the APM 2.6 board I will no longer require to use the power module?

I opted to use the APM on the helicopter as I have used one on a quadcopter and it works fine. The loiter mode is useful for camera use and the 'return to base' switch is useful in case of orientation and will return the drone back to base.

[Allan Bennett]

Posted by Eric Hartley on 07/03/2014 08:53:26:

Hi

The UBEC I have is the Hobbywing(from Giant Shark) 5A MAX 7.5A which apparently is the switching type and therefore if I leave the 'jumper' connection in place on the APM 2.6 board I will no longer require to use the power module?

I opted to use the APM on the helicopter as I have used one on a quadcopter and it works fine. The loiter mode is useful for camera use and the 'return to base' switch is useful in case of orientation and will return the drone back to base.

Your stand-alone BEC ("UBEC" is a trade name for a specific brand) sounds okay to me, provided you're doing gentle flight which doesn't exercise the servos too much. And what you say about the jumper is the way I read the APM instructions. I must stress here that I've never used one though, so don't take just my word for it.

Also, are you sure that something that works on a quad is going to also work on a heli? On a quad the controller is juggling four ESCs to keep the thing level, but with a heli it's a completely different control method, with programmed mixes between the three swash servos, plus the tail servo working independently.

[Eric Hartley]

Hi

Yes according to the Arducopter website instructions the APM 2.6 will work ok with a normal helicopter. In the firmware on the mission planner there is an option for installing the data for helicopter. However it is recommended that your Tx is set up for aero. rather than heli!

[Allan Bennett]

Good luck. Let us know how it goes. Hopefully someone with APM experience in a heli will be around if you need further help