hookedonrc

Read something that threw me. I am going to build an electric version of the Kadet Sr. and it calls for standard servos. This is not my first electric plane, but the first one that doesn't already come with a matched power plant. I am considering Hitec Standard HS 430 BH servos and in the notes it shows them rated to Nimh 4-7 cells, or a 2S Lipo's. I am using a 4s lipo for power and am now wondering if this means I can't use the Hitec's?

scale only 4 me

My Feedback: (158)

Typically your ESC will have a BEC, the rx/servos will power off of that @ around 5 volts.

Otherwise, you'll need a separate battery source for RX/Servo power, or a separate BEC

hookedonrc

Thanks, yes the ESC does have that so it looks like I am ok. I knew about the low voltage shut off, didn't even think about the regulator part. That's what I get for researching before I have had my morning coffee.

KW_Counter

This servo is rated at 6.0 to 7.4 volts.
If your BEC is putting out 5.0 volts you may have a problem.
You need to do some testing.
You might make this inquiry on the Hitec forum.

Good Luck,
KW_Counter

scale only 4 me

My Feedback: (158)

Likely those servos would be fine, but run a little slow @ 5volts,,
If your ESC doesn't have selectable voltage output an external BEC might be the answer,, or a second flight pack,, to take full advantage of the servo speed/torque

good luck

jester_s1

Those aren't the right servos for your application. Choose one that is 4.8v-6v and enjoy your plane.

scale only 4 me

My Feedback: (158)

omg, Why? No reason he can't run those servos if the BEC output rx/servo voltage is correct

Rodney

Nothing wrong with using those servos.
They will work fine for you powered off a typical ESC which will probably be at about 5 volts.

hookedonrc

Here is the ESC that I am using with a Rimfire 32 as the power plant. A 4S 3300 MAH Lipo battery is the source.

Eflite
[h=1]60-Amp Pro Switch-Mode BEC Brushless ESC (V2) (EFLA1060B)[/h]According to the manual with the ESC, this is straight from it:

• Drive up to 7 analog or 6 digital standard-sized servos with the BEC on any recommended input voltage
• 3- to 6-cell Li-Po, 9- to 18-cell Ni-MH/Ni-Cd input voltage

scale only 4 me

My Feedback: (158)

Looks like that BEC is fixed at 5volts, like I said befor, those servos may run a little slower than the 6.0-7.4 volt ratings.

hookedonrc

No problem with that....I am not planning much with the Kadet Sr. First, it is my first foray into electric from the standpoint of putting the pieces together. I have been buying foamies for awhile now. And, my plans for this plane is practicing my takeoff and landing rolls. Been out of flying for awhile and am very rusty on that part of flying. I can always switch out later for better performance if I want.

Gray Beard

My Feedback: (-1)

I know almost nothing about the electric stuff so before I buy any gear for a new plane I go to the bottom of the header and go over to the wattflyer site to get the information I need. It's really a nice site with some great people.
I see nothing wrong with your set up other then the servo speed but big whoop, that plane isn't a ball of fire anyway.

scale only 4 me

My Feedback: (158)

The castle 10 amp external BEC is only like $22 at Tower,very easy to add later if the servos under perform

good luck

All Day Dan

My Feedback: (5)

Hooked, there is an awful lot of complex circuitry between your R/C system and battery when you use the BEC. A much more reliable hookup is to use a separate battery pack for the R/C. ESCs do fry every now and then and that means you’ll lose you plane if you use the BEC. If you had a separate battery pack on board you could just glide back to mother earth. The plane you’re using is large enough to accommodate it and batteries are cheap. Dan.

hookedonrc

Dan, that's a very good point. I have very little weight with this plan anyway. And I have some spare 6v 2200 mah Nimh's sitting around that I could put to use on the RX and servos. I think I will do that.
i found out what I did, I accidentally picked the HV servos instead of regulars. And they are already shipped....so the separate battery makes perfect sense and is essentially free.

All Day Dan

My Feedback: (5)

Thanks for the thought. Cycle those spare batteries to make sure they still have their capacity. Unused batteries deteriorate quickly. Dan.

hookedonrc

Yep, that's my plan.

OliverJacob

My Feedback: (12)

When you use a separate receiver battery, you may run into problems by connecting it parallel to the BEC speed controller.
In that case, it's better to get a controller without BEC.
The controllers are very reliable when not operated at their current limit. You should be fine with using your Lipo as rx battery. I have several setups and only had one controller fry because the motor was shortened out. In that case it still provided power to the rx and I could land safely

speedracerntrixie

My Feedback: (29)

+1 usually if you hook up the BEC and a separate RX battery you will smoke the RX. Been there done that. The fix is to remove the positive pin from the ESC connector and throw a peice of shrink tube on it.

hookedonrc

It seems that my best course of action is either to just use the lipo and HV servos as planned. Or to just buy the right servos and move on. I am not purchasing the most expensive ones anyway.

jester_s1

If you already have the servos the plan of removing the + wire from the throttle lead and insulating it will work just fine. You can use a hobby knife to lift the tab that holds it in which does no damage. If you ever want to put it back, you push it in until it clicks. Doing that will disconnect the BEC but still allow the throttle signal for your ESC to work. Then you can run any receiver pack you want to.

All Day Dan

My Feedback: (5)

Good point guys. The red, plus side of the batteries, has to be removed if you are going to eliminate the BEC. Dan

hookedonrc

I am leaning more to removing the positive pin from the throttle lead. I am assuming that it is the positive lead on the throttle servo? Or am I confused.

OliverJacob

My Feedback: (12)

The 3 wire lead between your speed controller and the receiver has likely a red (+), a black (-) and a white or yellow (signal) lead.
You need to interrupt the red one, this is the positive lead. Otherwise the receiver tries to provide power to the controller, which has it's own
power supply (BEC). Then the BEC would try to regulate the rx battery down to 5 Volts and something would start smoking...

Rodney

You are correct. Just remove the red wire (center pin on the connector) on the connector that goes from the ESC to the receiver. Then you plug the external battery (can be either a 4 or 5 cell Nixx type) into any unused slot on the receiver. This will power up the receiver and the servos. You can use the point on an Xacto knife or a pin to lift the little tab on the connector pin and then pull it out of the connector. Just insulate the pin so it does not short out to anything as it will have 5 volts on it as the ESC is still supplying 5 volts to that pin even if it is disconnected. Now, if you ever want to use the ESC in the conventional manner, you can reinsert the pin in the socket to restore it to it's original configuration.