[Da Tow'd]

Hi Gang,
We have been building a 12ft. G38 powered trainer.






To break in the engine I strapped the plane to my auto hoist and ran two tanks for fuel through it.
I had to test the controls and I must have smoked the rudder and elevator servos, both are HiTecHS645mg. I pulled the bottom cover off one and see the printed circuit board is burnt. Since then I bought two HiTec HS5645MG and thinking about ganging them up to run the rudder. Using a dual servo tray. Maybe also have to run dual servos on the elevator.

Could my setting be way off on the DX7 to cause both servos to fail?

Any idea what would cause the servos to burn out?
any thoughts?





our aircraft carrier

thanks
hank

[itizme]

Sounds simple like too much voltage. For you to fry two servos at the same time must mean something common
Any chance your exceeding mx 6vdc for those servos?
OR
Any chance your servo wiring is somehow crossed up, maybe something like wrong pin outs on home made extensions?


Hope the new ones serve you well
Cheers

[Da Tow'd]

Thanks for the reply
We have a 2200mHr/11.1v lipoly battery and have it going into the battery port on the receiver.
I looked at the packing that came with the servo and see that it runs at 4.8V--
I don't have any voltage reducer to drop the 11.1v to 4.8v.
I just assumed that the servos operated at 11.1v.
so I better start checking on the servos voltage
thanks
hank

[itizme]

oops
Do not connect that battery again, you could loose the receiver as well.

Recheck with a 4.8 or 6 volt pack, I suggest the proper voltage pack instead of a regulator. Keep It Simple.
Cheers
Steve

That would cook it. Probably ruined all the servos that were hooked into the Rx and the Receiver too.

I see you have a Spektrum Transmitter, so I assume your using a Spektrum Rx. Most of the Spectrum receiver can handle up to 9.0V. A lot of the common servos will handle up to 6V.

Are you running electronic ignition in that plane, and was it hooked up to the Rx in any way?

[Da Tow'd]

heck of a learning curve and starting to get expensive

the engine is a Zenoah G38 2 cycle gas

back to the drawing board
cheers
hank

[Da Tow'd]

having taken time to reflect on my goof up = overvoltage and smoking those servos
I'm wondering if using a brushless speed controller just for the bec to supply the power to the receiver, so I can keep the "big"11.1v lipoly instead of buying another battery.
trying to keep it simple as I have extra controllers
thanks
hank

[itizme]

be very careful, you can easily brown out doing that. Big planes equal more current, you could be building a crash into your set-up.

[cravenjw]

I agree with steve most esc only give about 5A for servos. Plus the higher the input voltage or cell count, the less they can output, because they have to disapation the over voltage as heat.

You can put a castle pro bec in, 45-50 bucks, give you 20a on 3s input. Nice heatsink. Only 29g. You can set the output voltage with a castle link (usb to pc) . From 4.8v to 12.5v. Comes set at 5.1v from factory.
For standard servo, output at 6v, a 2s bat is perfect. But 3s will be work, it will just be a little less efficient, generating more heat. You use 400mah per flight rather than 300mah.

There are other similar becs/regs, but this one is easy to get, light, good quality and reasonable priced. I must have at least 6 of them. Set the voltage (if necessary), install it and forgot it. If you fly at a club, likely somebody has a castle link and can set the voltage for you.
Good luck.

[HAL9KPCM]

A little food for thought... and maybe I'm just paranoid, and maybe that setup works for many people without issue, but here's the way I see it. I put that same kind of setup in my helicopter. Radios have changed a bit in the past two decades since I've flown and I put in a higher voltage battery along with a CC voltage regulator at the recommendation of the sales person at the hobby shop. Then I got to thinking, I just put a $40 device in between my battery and my receiver. I just added an additional failure point to a $3000 model. A faulty or cheap capacitor in the circuit of the regulator and poof, no power to the system. At least with a battery sharing device which essentially uses diodes which are resilient little pieces of hardware which are less likely to fail and the inherent design of such devices that if a failure did occur, it would be most likely to occur on only one side leaving at least a possibility of maintaining control.

I finally went with a battery sharing device and dual batteries. I needed the weight in the nose anyway and now have more capacity.

Just something to think about.