Mod: Feedback wire for Bluebird BMS-385MAX (Completed)

[Kevin_Erik]

Stared work on the 385Max or just “Max” for short, to see if it is possible to add a feedback wire just like with the BMS-210.

Bluebird product info: https://www.blue-bird-model.com/products_detail/76.htm

Thus far, things are going well but I can say that the servos internal setup is a little bit different from the 210’s. Specifically the Potentiometer is positioned to the front of the Servo case and appears to be glued-in. (Can not remove it) Hence it seems that the only way to connect a wire is to attach directly to the point where the Potentiometer meets the PCB card. Overall though the Max’s internal arrangement allows it to use a larger motor and thus produce more torque. (Hopefully less likely to fail as a result)

[Kevin_Erik]

Case and motor.

Potentiometer from front.

Potentiometer from back with motor removed.

Feedback with soldered at point where Potentiometer meets PCB.

1.5 – 2mm hole for feedback wire.

Used hot glue to further secure wiring.

Assembled.

Gota love heatshrink!

[Kevin_Erik]

Did a quick “functional” check to make sure that the servo isn’t going to short circuit.
So far so good!

Will next add the feedback wire to the Copters RSSI input (remapped) and see if I can perform a tail tune using this setup. (Could not previously with the Max)

Kevin

[Kevin_Erik]

Success!!!

Video of functional test that includes the feedback wire.

[Kevin_Erik]

Fully assembled the Copter and performed a quick in-house test flight.

So far so good!

Will do an outside Tail-tune once the beeper arrives. (1-2 days)

[Kevin_Erik]

Feedback wire voltages verified, Left: 0.963V, Mid: 1.647V, Right: 2.346V

[Siclair]

Looks good.

Benefits of using this particular servo?

[Kevin_Erik]

Its a bit bigger, has a better motor (torque) and thus should be able to take a hit.
Weights about the same and uses the same voltage so not really a down side here.

[Author]

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