Digital tail servo on non-digital gyro

[joskibob]

Doesnt using a digital tail servo with a NON-digital gyro burn out your servo?

Or does it not make a difference.......

I have a s285 that i would like to use on my falcon 3d tail

[vera]

It's the other way around... if a digital gyro thinks it's talking to a digital servo but it's not a digital servo then it will likely burn out the servo. A digital servo on a non-digital gyro is not a problem. The advantage of a digital gyro and a digital servo together is that the gyro can update the servo much more often. The GY401, for example, is able to talk to a digital servo or a non-digital servo, but you have to set a switch on the gyro to tell it which servo it's dealing with.

[joskibob]

sweeeeeeeeet so i can throw that servo on in place of my bunk ass tail servo, and the 2 cyclic servos :) :) :clappp :clappp :clappp :clappp :clappp :clappp

[Iceman140]

vera-

hey at what point does the current carrying capacity of the servo connected to the gyro come into play? Do all the more elaborate gyros indicate the overall current they expect to draw through the circuit ?
:dontknow
Ed

[vera]

Iceman140

The gyros and servos I have don't provide any current load info. If you're concerned about the load capacity of the wires I don't think that's any issue.

The gyros don't supply much current to servos, only just enough to send the signal, which is very small. The current for the servo motor comes from the gyro connector, but that's just jumpered right over from the input to the gyro. So the gyro isn't actually supplying motor current to the servo. Gyros themselves don't need much current, I'd say it's less than the receiver. Servos are the power hungry critters.

[Iceman140]

VERA-

The way it was explained to me is that some part of the gyro is in series with the servo motor and the main reason you need a higher current capable servo for the tail. Do some gyros feed the tail servo directly? I'm not worried about the wires, but if the gyro is indeed in series with the servo, then current drawn thru that circuit goes thru both, and I've always understood that this is the reason tail servos burn out. Hmmmm...

Ok, just re-read the book. Seems the gyro can send very high current to the sevro, compared to the collective servos, but the gyro circuitry itself uses little current. It seems battery capacity plays a part too in what manuvers you're doing. 1000mAh for general flying and 2000mAH recommended for hard 3D flying to provide enough current for all servos and motor working together. Clear as Mississippi mud now! :mrgreen:

Ed

[vera]

As far as power supply goes, the receiver and gyro and all the servos are in parallel. Servo power doesn't pass through any gyro circuitry, the gyro is just a tie point for servo power. The only thing the gyro sends to the servo is a pulse of a certain width, at a certain rate, which indicates where the servo ought to be. This is a very low power signal and it doesn't drive the motor. The servo looks at that signal and compares it to a signal generated by itself which depends on its position, and the servo then decides what to do with the motor based on that. The power to run the motor comes from the gyro, but in the gyro that connection is jumpered over to the wire coming into the gyro, so the gyro has nothing to do with it. It's a "T" connection... power comes in to the gyro, the gyro taps into it, and the servo taps into it.

The thing that burns up a non-digital tail servo when it's being driven by a gyro that thinks it's talking to a digital servo is the fact that the update rate is way too high. Each channel gets updated from the transmitter 50 times a second and the non-digital servo isn't designed to be bothered any more often than that. The digital servo circuit is designed a little differently, such that it can accept an update much more often. A gyro that's designed to work with a digital servo will send an update to the servo on its own several times in-between TX updates. The non-digital servo can't handle that flood of information. :WOW

The GY401 gyro has a switch to select the type of servo connected to it. The switch can be set to non-digital servo even if you're using a digital servo. It just won't get updated as often. But if the switch selects a digital servo and you're not using a digital servo then the update rate will swamp the servo and prolly burn it up.

[Iceman140]

Absolutely! Kinda reminds me of an SCR, only different. :mrgreen:

Ed

[vera]

:mrgreen:
It's actually like a retriggerable one-shot that gets triggered more often than its timeout duration... it just stays on. Even a digital servo takes a break between updates... a long break or short break depending on the amount of error.

[Iceman140]

An every watching SCR, always willing to put in it's 2 cents in addition to the user input. I think I worked with a guy like that once. :lol:

[BarracudaHockey]

The frame rate from a 401 is 270hz btw, vice 70 from the reciever.