DS650 Servo Issue

[pjbrazendale]

Hi,

Was doing my setup on my AR7200BX at the weekend in my 700n and I noticed that after setup when moving the rudder stick left and right the tail only moves every so slightly in either direction. The servo was not hot and my Sahara reg is only outputting 6V to the rx so I am surprised if I have killed it. However when there is no power to the servo it can be moved with ease with no resistance what I want to know is have I killed it and if so any ideas why as I thought they were rated for 6V. Also it was set to the correct frequency and pulse length based on the beastx website.

Cheers in advance

[Stevec]

have you tried plugging it straight into the RX without using the beastx?

if not do that and see if the servo is working, if it isn't then it is probably toast, if it does work then it sounds like settings in the Beastx.

happy testing
/Steve

[cjcj1949]

I'm a ex design engineer and the conclusion I've come to is that servos may work at 6V but not necessarily for as long as they do at 5V. Especially digital. They can provide lots of current and unless specially designed for 6V are better off running at 5V. 5V will always be more reliable. It is probably cheaper to buy better servos than run them at 6V. Digitals are very easy to destroy if they can't reach the desired position, and that can happen after a crash until you can turn off the power.

[1chris]

I have had align servo's on cyclics and tail running on 6.6 volts for 3 years now in four helicopters and hundreds (500) of flights between them with no problems, do not agree with all that

[jasoncook]

Are you sure you have the servo set right in the beast 333 and 1520 of the top of my head, I had a similar problem on a 251 would only move a small amount ?

[pjbrazendale]

Cheers guys for the input looks like servo is toast been through everything and double checked it think I've just been unlucky with it, may try something different on the tail going forward.

[cjcj1949]

I have had align servo's on cyclics and tail running on 6.6 volts for 3 years now in four helicopters and hundreds (500) of flights between them with no problems, do not agree with all that

You've been very lucky then. Lots of others haven't. Anyone who wants reliability wants to go for the lower voltage. Perhaps the servos built years ago were better. I've had no problem with a DS520 on cyclic. DS410s seem a problem and MKS advise special voltage regulators for each servo. I'd expect servos to work reliably at 6V but I'd feel happier if I'd seen a spec for the chips they use. It shouldn't be difficult to regulate the 5V to any chips and transistors should be able to work at 6V.

[1chris]

My servo's on the 6.6v life batteries have all been 610's, 620's and 650

[cjcj1949]

That's not 6.6V. That's just a nominal figure. Full volts are a lot more (7.2V). Useful to know. I thought people were complaining about the cost of high voltage servos. Those are Align servos? I just used an MKS servo on 5.6V and it died. MKS say no more than 5.0V. Even 4 NICds would be too much. The lower the volts the longer they will last.

[cjcj1949]

There seems to be a difference of opinion in this area. My experience is with the big old servos that never blew up and the 450 size digital that seem to have problems. There are no proper technical specs and it is difficult to know what is really going on. If you can monitor it with telemetry it would be interesting to know what voltage the servos are getting in use. You will need to measure this very close to the servo, ideally by soldering to the pcb. The bigger servos can take a lot of current and the volts will drop due to the connectors, thin wire and the load on the battery. This is probably very good as the volts will drop a lot when the servos are stalled and this may stop them failing. A BEC will keep the volts up and a high current BEC will be more likely to damage servos when they are under high load. There is also the frequency to consider and the combination of flybarless and Life may be too much, from the posts I've read. If you improve the power distribution your servos will work better, but not necessarily for that long.