Servo voltage issue

[v3dg]

Ok so I removed an old Savox 1230 from a previous build that seemed to be working perfectly to a new build I'm doing. When I powered it on the first time the servo was stuttering when turning slowly. I decided to check the voltage from the receiver and was getting 4.01V on the servo port. I checked with a servo extension wire that I cut up to easily use a multimeter on wires, not sure if this method is flawed... I am also using an old 10A Castle BEC (the one with blue shrink wrap over it).

Anyways after discovering the voltage issue, I then purchased a Castle link.
The voltage was set to 5.1V (even though I was getting 4.01 from the Rx) but then I changed it to 6V (the max that the servo can accept) and after checking voltage again (from my maybe flawed way of checking) I am now getting 4.91V.

Should I adjust the BEC until I fully get 6V to the port or is there maybe an issue with my Rx? I am using a Radiolink R6FG...

[diezel666]

I wouldn't suggest to keep upping the BEC voltage.

On my Futaba and Sanwa RX-482 (and the clone of the RX-482) that I have, all of the pins + and - are on the same PCB rail. Basically all the + are tied and all the - are tied together. With 6.45vdc into my receiver, I'm seeing 6.45vdc on all the pins + & - pins.

If you have confirmed the BEC is actually sending out 6.0vdc,
I'm thinking you either have:

• Something else plugged in that is drawing an awful lot of power and sagging the voltage down.
• A bad solder on the RX board that is causing resistance.
• A bad RX unit that is drawing a lot of amperage.

[ferp420]

is the gyro turned on that could be the source of the power draw
just a thought

[v3dg]

Originally Posted by diezel666

I wouldn't suggest to keep upping the BEC voltage.

On my Futaba and Sanwa RX-482 (and the clone of the RX-482) that I have, all of the pins + and - are on the same PCB rail. Basically all the + are tied and all the - are tied together. With 6.45vdc into my receiver, I'm seeing 6.45vdc on all the pins + & - pins.

If you have confirmed the BEC is actually sending out 6.0vdc,
I'm thinking you either have:

• Something else plugged in that is drawing an awful lot of power and sagging the voltage down.
• A bad solder on the RX board that is causing resistance.
• A bad RX unit that is drawing a lot of amperage.

Thank you very much for the help. For some reason I was only checking from the servo port and not the BEC itself to eliminate possible problems. I tested the voltage from the BEC and I was getting 5.1v and then thought the changes from the Castle link didn't stick but then realized the voltage kept going up very slowly. Like about 0.01 every 4 seconds. I waited about 7 minutes for it to go up and finally settled on 6.02v. I then disconnected the battery and reconnected multiple times and I seem to always get that good voltage now which raises another question... Is this normal in any way? Do BEC's need this much time to adjust to a stable voltage and stay there? Anyways it's working now so I'm 75% satisfied, not sure if I should change it now.

Originally Posted by ferp420

is the gyro turned on that could be the source of the power draw
just a thought

Thanks for the input. That would of been a good idea to check but it was off. Problem solved by itself apparently...?

[diezel666]

Originally Posted by v3dg

I waited about 7 minutes for it to go up and finally settled on 6.02v. I then disconnected the battery and reconnected multiple times and I seem to always get that good voltage now which raises another question... Is this normal in any way? Do BEC's need this much time to adjust to a stable voltage and stay there? Anyways it's working now so I'm 75% satisfied, not sure if I should change it now.

No, they should not have a "ramp up" time or soft start style feature at all, honestly rolling a lower voltage to a DC device to gradually bring it's voltage up would not be a good thing - unless large capacitors (far excessive to the use and size we would see in RC) are in use.

With Voltage there is a direct relationship to amperage (Ohm's law). Lower voltage = higher amperage needed to do work.

This to me sounds like something else is going on. I wonder if the capacitor on your BEC is faulty and is initially resistive and charges slowly. Sadly there is 3 ways to find out. And I don't recommend the them unless you're really comfortable with electronics.

One: Bypass the capacitor. Remove it, use a jumper wire around it.
Two: Remove it and test it, if you have a LCR meter.
Three: Replace it.