There was discussion today about external BEC's, so I thought I'd share this article I wrote for Crawl Australia/New Zealand. Even though it's based on surface application, the process and requirements are the same for rc aviation.
This is one method of installation, there is another (which is my preferred) that I will add later, in the next few days. The basics of that are:
All 3 control wires from the ESC go to the receiver. These power the receiver from the ESC's onboard BEC. I run the signal wires from my servos to the correct channel ports on the receiver, so they get their instructions the normal way. Then, I run the + & - power wires from my servos to the output wires on my 16 amp UBEC (which takes it's power from the battery plug that also feeds the ESC).
----------------------------------------------------------------------
History for you:
BEC stands for Battery Eliminator Circuit, and were first commercially introduced in the mid 80's.
Their purpose was to eliminate the need for the 4 AA (UM3) batteries needed to power the receiver and servos that were needed back in the day (and still are, or a battery of some description in nitro).
The drive battery was 7.2v ~ 8.4v and then, surface receivers could only take 6v max before they made the brown smell, so you could not just hook up a feed wire from the mechanical speed control (MSC) into the battery port on the receiver.
People started doing this with a diode pack or resistor inline, but found out that when the motor was under heavy load it would steal power away from the receiver and cause momentary loss of control.
Tamiya, Accoms and various other manufactures introduced a transistorised BEC that levelled out the power fluctuations and gave a constant 6v to the radio until the battery died, resulting in the servos sticking in their last position, which was normally full speed into something
1990ish on, BEC's were built into entry level receivers and standard inside ESC's (electronic speed controller). ESC's manage the power to the receiver to the point you could drive until the motor didn't have enough power to move the model but you still had control of the steering and throttle.
Now, modern BEC's.
The BEC in a ESC is normally capable of delivering 1.5 amps to 5 amps to the radio before it burns. This is fine for running one high performance servo in a race car or buggy.
Basic BEC installation
Piggyback the BEC power wires to your ESC's battery plug:
Remove the positive wire from the ECS's receiver plug. Most can be removed by lifting the little locking tab on the plug with a hobby knife blade.
Bind the loose plug to the other wires with insulation tape. This allows for quick reinstallation for programming with a Castlelink or Firewire if applicable. Now plug the ESC plug into the usual port on your receiver. Plug the receiver plug from the BEC into a spare port on your receiver (a channel, battery or bind port will work). If you don't have a spare port, you can use a y harness and share a port with one of your servos.
Done!
This is one method of installation, there is another (which is my preferred) that I will add later, in the next few days. The basics of that are:
All 3 control wires from the ESC go to the receiver. These power the receiver from the ESC's onboard BEC. I run the signal wires from my servos to the correct channel ports on the receiver, so they get their instructions the normal way. Then, I run the + & - power wires from my servos to the output wires on my 16 amp UBEC (which takes it's power from the battery plug that also feeds the ESC).
----------------------------------------------------------------------
History for you:
BEC stands for Battery Eliminator Circuit, and were first commercially introduced in the mid 80's.
Their purpose was to eliminate the need for the 4 AA (UM3) batteries needed to power the receiver and servos that were needed back in the day (and still are, or a battery of some description in nitro).
The drive battery was 7.2v ~ 8.4v and then, surface receivers could only take 6v max before they made the brown smell, so you could not just hook up a feed wire from the mechanical speed control (MSC) into the battery port on the receiver.
People started doing this with a diode pack or resistor inline, but found out that when the motor was under heavy load it would steal power away from the receiver and cause momentary loss of control.
Tamiya, Accoms and various other manufactures introduced a transistorised BEC that levelled out the power fluctuations and gave a constant 6v to the radio until the battery died, resulting in the servos sticking in their last position, which was normally full speed into something
1990ish on, BEC's were built into entry level receivers and standard inside ESC's (electronic speed controller). ESC's manage the power to the receiver to the point you could drive until the motor didn't have enough power to move the model but you still had control of the steering and throttle.
Now, modern BEC's.
The BEC in a ESC is normally capable of delivering 1.5 amps to 5 amps to the radio before it burns. This is fine for running one high performance servo in a race car or buggy.
Basic BEC installation
Piggyback the BEC power wires to your ESC's battery plug:
Remove the positive wire from the ECS's receiver plug. Most can be removed by lifting the little locking tab on the plug with a hobby knife blade.
Bind the loose plug to the other wires with insulation tape. This allows for quick reinstallation for programming with a Castlelink or Firewire if applicable. Now plug the ESC plug into the usual port on your receiver. Plug the receiver plug from the BEC into a spare port on your receiver (a channel, battery or bind port will work). If you don't have a spare port, you can use a y harness and share a port with one of your servos.
Done!
Signature overload. That list just got ridiculous. However, Funcubs are .... fun.