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Graupner GR-24 12ch receiver

PWH-DXB

Junior Member
#1
Hi guys, I am running the MZ-24 and GR-24 Hott system in a big scale scratch build balsa P-38. With a multitude of servos, multiple on same channels via Y-leads, and 3 power-hungry electric retracts, am I in danger of overloading the receiver? It seems like a lot of amp draw thru that little box. Any ideas?

Thanks,

Pete
 

Foam Addict

Squirrel member
#2
First off, Welcome to the forum!

Yes, that's a lot of current through those little traces.

I would set it up so that the receiver has a separate UBEC to the Batt port, then run just the the + and - leads to a massive UBEC to run the servos and retracts, and finally run the signal and a second set of ground wires to the rx so power isn't running through it, just the ppm signal. Someone will have a better idea, but I'm using this on my Dehavilland Mosquito with great success.
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#3
Hey Pete, Welcome to the forum!

I'd worry far more about your UBECs not being up to the task and either the receiver browning out or the servos not having the oomph to move as far as they need to.

You're almost certainly OK, but if you're concerned enough to do something about it, you can always create a separate power/ground rail to connect all of the servos to, then connect the signal lines to the RX -- the power rails can even be split among UBECs to distribute the load between them, but you'll need to keep a common ground for everything. You'll need one power and ground connection on the RX, but if you only have one, there's no way it can be used as a power bus and burn out.

BTW, don't be bashfull about posting pic's of your beauty -- we all love a good look at a classic model ;)
 

PWH-DXB

Junior Member
#4
Fantastic forum!

Thank you Foam addict and Crafty Dan for your quick replies. At the moment I am still trying to figure out the drive line setup, but the motors are O.S engine OMA 5025-375, ESC's are O.S. OCA 280, with a pack of 6s 4500mah 50C each. Props are Master Airscrew 14/9*3.

None of it is connected yet, as I still have a lot of reading to do, with regards to how it all goes together. This is my first venture into electric flight, so I better get it right. The idea of a separate power rail is what I had in my minds eye, I just needed your input on how to do it, so thank you very much indeed.

I am about to upload a photo of the whole thing, but as it is my first attempt at doing so, bare with...

Thanks again :) IMG_7632.JPG
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#5
Now isn't she just a beauty in the making!

I take it elevator goes down one boom and rudder goes down the other? 2 servos for ailerons in wings or one in the main fuse?

Flaps? single/dual servo?

Planning a single battery pack in the center fuse, or one in each boom?

UBECs in the ESCs or an external BEC to power servos?

Sorry for the detail questions -- there are easier ways than others to lay out the electronics and they vary a bit depending on what goes where.
 

PWH-DXB

Junior Member
#6
The plan is ubecs and separate battery packs, one in each boom. There's 2 servos in each boom, 1 for rudder and 1 for elevator. 1 servo in each wing for ailerons. No flaps at the moment. Looking at an AUW of 6000g. Servoless electric retracts, with nose wheel steering. I'd like to program the setup in a way that the nose wheel and rudders work together,but as soon as I hit retract the nose wheel centers and disconnects. Lots to learn! I am looking at making gear door switch micro servos and 3 individual door sequencers. Will see how I feel about it later.
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#7
Seems like a shameless plug, and not *quite* what you're doing, but the idea can be extended:

http://flitetest.com/articles/simplified-twin-control-harness-for-the-kraken

The first row on that can be repeated three more times with a second servo extension to move up to 5 signal lines from one nacelle to the other. Need more? Keep adding rows. Just be careful to not bridge the power buses together -- space will get a little tight, but it should all be manageable.

The beauty is it creates a nice power bus on the slave pod (non-RX side). That design has the master pod using the RX for the power bus, but it can just as easily have another harness block on that side, so long as you break off a pigtail of power and ground for the RX. You'll also need to run a harness to the center fuse to run the nosegear, and with it also power and ground.