I have a question about bec. Is is the speed control or the receiver that dictates whether or not you can use BEC? The throttle is channel 3, so do you just plug the ESC into there and the reciever has power? What reciever could I use to get power from this?

http://www3.towerhobbies.com/cgi-bin...?&I=LXMGL8&P=V

Thank you.

The specs on that ESC say "BEC: 5V/ 2A max". That means the throttle lead will supply 5 volts to the receiver. This is enough for most, but not all receivers. The disclaimer is because I know of several receivers that need 6 volts to operate properly. And you're right, just plug that into the throttle channel.

I've never heard of a 6v receiver, but I don't claim to know all of them. Which RXes require 6v? I'm just curious.

Any RX (that handles the voltage) will work with a BEC. In the same way, you can plug a normal battery into any channel opening, (most) RXs just don't care where the voltage comes from. I often plug the battery into a random channel opening instead of the "Battery" plug. Some RXs don't even have a dedicated battery plug, they just expect you to use an unused channel, or a y-harness.

The biggest issue with using a BEC is the "2A" part, and the way the BEC drops the voltage from the flight pack.

First, most BECs are only rated for 3 or 4 servos. That's the "2A". If you use digital servos, or put a large load on several servos at once, you can draw a lot of current. Draw too much, and the BEC can't deliver it all, and either something burns up, or the voltage drops to the RX and you loose radio contact for a split second (or longer, depending on the RX and BEC).

Second, many ESCs have BECs that can be used if you're using a 2 or 3 cell Lipo pack, but not if you're using a higher number of cells or they have some other limitation. The reason behind this is that the BEC built into the ESC isn't always the best at dropping down the voltage without wasting a lot of power and creating a lot of heat.

There are seperate "switching BEC" devices out there that will handle larger servo loads and higher input voltage. They are using better design and componets to handle more power though the system without burning up.

Lets start by seperating terms, ESC and BEC. Most but not all ESCs (Electronic Speed Control) have a built in BEC (Battery Elimination Circuit) you can also buy a stand alone BEC that is not an ESC. The one you have posted contains both circuits.
All that said, unlike Piper Chuck, I do not know of any receivers that require 6 volts so I will have to take his word for it. Double check before buying.
We can't recommend a receiver until we know what airplane this is going in and what transmitter you will be using. ie... if it is a small park flyer you will want a micro receiver...

Here are a couple:
http://www3.towerhobbies.com/cgi-bin...&I=LXRAZ5&P=ML
http://www3.towerhobbies.com/cgi-bin...&I=LXLZP0&P=ML

Interesting. Those are 3-channel surface receivers though.

Yes, they are 3 channel receivers. However, once one goes to 2.4, does the surface/air limitation even apply? I don't think I'd want to try flying a plane with a pistol grip radio, but Futaba does make a couple 3 channel stick radios. I've been considering switching to 2.4 and had considered a 6 or 7 channel Futaba so I could use it for boat and planes. Unfortunately, the low battery failsafe in the 6 and 7 channel FASST radios is setup for 4 cell batteries and I use 5 cell in most of my boats and several of my planes. But anyway, I stray too far from the original topic...

Yeah, I got a Spektrum AR6100 receiver that I planned to try out in a surface vehicle (with my DX7 transmitter). I originally planned to put it in a boat, but then I heard that people have had problems with the 2.4GHz DSS systems in boats (the water's surface supposedly screws up the range somehow). I might still try it in a car, but I like pistol grips better for cars.

Futaba's FASST system has been extensively tested in race conditions and has been shown to be very reliable. Other vendor's systems seem to still need work before they can be used in boats.

so this setup will work fine:
this receiver

R156F, http://www.rcuniverse.com/pgarchive/Futaba_R156F.htm


getting power from the previously mentioned speed control?

Yes that receiver will work with that ESC/BEC.

ok thank you