Utilising both BECs in the FT Cruiser

by hotwax | May 3, 2013 | (9) Posted in Tips

If you are using ESCs with switched BECs, or if you are not shure wether one BEC alone can power all the servos in your FT-Cruiser, you may be interested in my solution.

(caution: bad german english perfectly spoken)

You power one half of your RC Gear with one BEC and the other half from the other without connecting both circuits.

Note: Spektrum users must always power the Rx from the throttle channel

The ESCs I use have 3 linear regulaters each. They can handle 2 - 4 Cells. The BECs are ratet at 3 A. As a rule of thumb the 3 A are delivered only if using 2 Cells. At 3 Cells there will be 1.2 A and at 4 Cells only 0.7 A available. The reason is, that linear regulaters get hotter when the voltage difference raises. So if you beef up your plane, you weaken your power supply. Dividing the load will help preventing brownouts.

Combining thottles is one VMIX (Channel 3 Master, Channel 8 Slave). Mixing Rudder to the ESCs is made by two VMIXes in my Futaba. Channel 4 Master Channel 1 and Channel 8 Slave.

COMMENTS

Pauloar on May 6, 2013
Echt sehr Gut!!!! Können Sie ein Zeichnung oder Bilder für Ihre Template her laden?

Alles Gutes,
Paulo.
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hotwax on May 7, 2013
done
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OutcastZeroOne on May 8, 2013
And I thought my article about custom making a stand alone BEC was complicated...
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hotwax on May 8, 2013
If your profession is german taxes, nothing is complicated ...
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apache64 on May 8, 2013
Sehr Gut Idee, a more simpler idea, but could you not just connect the two 5volts together as they are linear Regulators, they wont let back voltages through, and thus share the load better? Otherwise if one bec goes you loose half of the equipment, but it is then 50/50 which half, Rx or just servos.
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hotwax on May 8, 2013
Simply connecting all BECs means in my example 6 7805 regulators im parallel without synchronisation. This may work well, this may become hot and weak depending how similar the 7805s are. Differencial use of the ESCs will worsen the situation. Using switched BECs, connecting is just not working.
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hotwax on May 8, 2013
But you are right, if one circuit fails, the plane goes down. This should be avoided at any costs.
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danallen82 on May 16, 2013
So its okay to share the ground between the BECs?

I wonder if there is a way to properly combine the 5v outputs as a backup for the receiver.
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Kurt0326 on September 20, 2015
I really enjoyed your diagram. I don't know how I missed this article. Now I am starting on an advanced ft cruiser build and I was wondering if you might be able help out with the wiring. Can you help, please?
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Utilising both BECs in the FT Cruiser