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Old Feb 07, 2005, 06:16 PM
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United States, NJ, Raritan Township
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BEC, SBEC & UBEC Difference Between Them

I am interested in trying a separate battery to run all my electronics but I have no idea what the difference is between BEC, SCEC & UBEC. Could someone help me with this topic?

Thank you
Mark
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Old Feb 07, 2005, 06:56 PM
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Not sure I fully understand the question as when using any type of BEC, (Battery Eliminator Circuit) you negate the need for a seperate battery. One of the many advantages to electric IMO.

BECs onboard an ESC ( most ESCs have them) are only rated for x number of cells and y number of z type of servos. Exceded either the voltatge or servo count, and you can not use the onbaord BEC. ( well you can for about 2 minute ) The Ultimate BEC (UBEC) is external to the ESC. You disable the ESCs BEC. The input to the UBEC is connected to the battery ahead of the ESC, and the output of the UBEC is plugged into the battery slot ( or any unused one) of the receiver and it acts like an onboard 4 cell pack, but without the weight, and extra maintainance associated with the extra pack.
Not sure what a SCEC is.
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Old Feb 07, 2005, 06:59 PM
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Obviously all three are BECs- Battery Eliminator Circuits.
The purpose of any BEC is to take the batter at say X volts, and convert it to 5 volts to operate the receiver and servos.
By using one you can eliminate the separate small receiver pack.
The standard BEC is a linear voltage regulator integrated circuit, or often two or more in parallel to increase the current capacity.
It functions by dropping the excess voltage across the device. The problem is that as you add cells the input voltage X increases and the power that the BEC has to absorb rises. This can cause it to overheat, leading to thermal shutdown. This is bad, since you will lose all voltage to the radio and servos until it cools down.
The practical limit is 10 or 12 round cells, although with adequate cooling 14 is sometimes possible.

The SBEC and UBEC both are switching voltage regulators. They work by taking pulses of energy from the battery, store it in an inductor and/or capacitor,
and then release it to the receiver at a lower voltage, in this case 5 ( or 6 ) volts.
The advantage over a linear regulator is that there is very little energy lost, so they will stay cool with inputs up to 40 volts.
In some cases the switching noise can cause interference with the receiver, but careful component placement can prevent that.
Hope that helps
Pat MacKenzie
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Old Feb 07, 2005, 07:06 PM
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Hi,

Thank you. What happens to ESC wire that plugs into the RX then? It just hangs thier loose? I have been having a problem where my Gyro shuts down in flight and I have heard it is more effiecient to run some type of battery elim circuit to power my electronics is this true?

Mark
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Old Feb 07, 2005, 07:22 PM
I don't want to "Switch Now"
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If your ESC has an onboard BEC and you decide to use an external battery,BEC, UBEC or SBEC, you have to disable the BEC in your ESC.
This is easily done by removing the red wire from the 3 pin ESC connector. You still need the other two to send control signals to the ESC.
Having said that, gyro shutdown is not normally related to BEC problems. You might just have a bad gyro or tail rotor servo.
Could you give more details of your setup?
Pat MacKenzie
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Old Feb 07, 2005, 07:30 PM
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Quote:
Originally Posted by pmackenzie
If your ESC has an onboard BEC and you decide to use an external battery,BEC, UBEC or SBEC, you have to disable the BEC in your ESC.
This is easily done by removing the red wire from the 3 pin ESC connector. You still need the other two to send control signals to the ESC.
Having said that, gyro shutdown is not normally related to BEC problems. You might just have a bad gyro or tail rotor servo.
Could you give more details of your setup?
Pat MacKenzie
Hi,

Sure here are the details:

Trex450X
CC35
4 Hitech Hs 56 Servo's
Futaba Gy401
TP 2100MAH 3S Pack
Berg 6 Channel RX Version 3
Ferrite Ring Interference eliminator
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Old Feb 07, 2005, 07:43 PM
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3S is too much for the CC35 onboard BEC.

You need to run an SBEC probably. The UBEC is a lot larger and heavier than the SBEC.

Toshi
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Old Feb 07, 2005, 07:44 PM
I don't want to "Switch Now"
pmackenzie's Avatar
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Did you get a rcvr pack with your radio?
If you have or can borrow one, try it and see if it solves your tail problem. If it doesn't, there is something else wrong.
Be sure to disable the BEC as explained above.
Pat MacKenzie
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Old Feb 07, 2005, 08:02 PM
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If you read the EHBG, you'll see the specs for both the UBEC and the SBEC in it.

Look in "Helicopter Parts Selection" and then "BEC".

Picture of the UBEC and SBEC. White blob mounted on the Raptor is the UBEC. The tiny circuit in the package is an SBEC.

Toshi
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Old Feb 07, 2005, 09:35 PM
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Quote:
Originally Posted by TMorita
3S is too much for the CC35 onboard BEC.

You need to run an SBEC probably. The UBEC is a lot larger and heavier than the SBEC.

Toshi
Toshi,
Thank you for your input but I know/see there are several people who run this setup and don't have any issue's, I am not questioning your experience but before I spend more money how can I be sure that adding a SBEC will Solve my problem? I also have the Corona with the CC45 and gy240 and I have the same problem "Sometimes" the commonality here for me is the CC products without a doubt. I looked at Castle's website and did not see specs for thier BEC as far as Volt/Amps would you have an idea?
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Old Feb 07, 2005, 09:49 PM
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Mark,
if you go to the CC website, click on the "Documents" tab and you can download the manual for the CC35.
The BEC is rated 3 amps, but on 10 cells they only allow 4 micro servos or 3 High torque servos.
So a Hornet with 4 x HS50 works fine on 3S, but 4 HS56 on the same 3S might be a bit too much.
I still wonder if your tail problems have some other source. BEC shutdown is usually quite dramatic.
The motor will stop and the helicopter will stop responding to any input.
Pat MacKenzie
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Old Feb 07, 2005, 09:59 PM
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Quote:
Originally Posted by pmackenzie
Mark,
if you go to the CC website, click on the "Documents" tab and you can download the manual for the CC35.
The BEC is rated 3 amps, but on 10 cells they only allow 4 micro servos or 3 High torque servos.
So a Hornet with 4 x HS50 works fine on 3S, but 4 HS56 on the same 3S might be a bit too much.
I still wonder if your tail problems have some other source. BEC shutdown is usually quite dramatic.
The motor will stop and the helicopter will stop responding to any input.
Pat MacKenzie
Pat,

Yes I agree everything else is working at the time but the Gyro.

Let me describe exactly what happened maybe I am confusing everybody.

Trex in the air about 25ft 2 minutes into flight suddenly tail would just spin out of control happened 3 times I would have manually try and hold the tail with rudder input to get it down safely. Last night in my garage I was hovering and saw the Solid LED on the Gy401 goto Blinking which is non HH mode then I crashed it. Now this has also happened on my corona I will list the specs for that below.

Corona Setup:
CC45
2- Hitec HS-85MG Micro Servo
1- hitec hs 81 For Tail
Berg 6 channel RX Version 3
8 cell gp3300
Mega 16/15/3
Gy 240 gyro
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Old Feb 07, 2005, 10:03 PM
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So since I am using a 3s2100 pack this would equal about 12 cells is this correct? I probably did not take this into consideration.

Mark
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Old Feb 07, 2005, 10:04 PM
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Quote:
Originally Posted by mcoccia
Toshi,
Thank you for your input but I know/see there are several people who run this setup and don't have any issue's, I am not questioning your experience but before I spend more money how can I be sure that adding a SBEC will Solve my problem?
...
Simple.

Run the T-rex for an entire pack, then land and put your finger on the BEC chip on the ESC. If it's burning hot, then you're overloading it.

I've used linear regulators such as the LM7805 to power digital circuits, and they're normally used to regulate 8 volts down to 5 volts. Consider that:

1. A linear regulator drops N volts down to 5 volts by wasting the excess power as heat,

2. An LM7805 is in a TO-220 package which is about three times larger than the surface-mount regulators used on the Phoenix series, so the LM7805 can dissipate a lot more heat,

3. An LM7805 is typically used for regulating 8 volts down to 5 volts @ 1 amp, so it's dissipating 3 watts as heat.

4. The tiny surface-mount regulator on a CC Phoenix is regulating ~12 volts down to 5 volts @ ~2 amps, so it's trying to dissipate 14 watts

So basically, the surface-mount regulator is trying to dissipate about 4x the amount of heat in a package that's 1/3rd the size of an LM7805.

Toshi
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Last edited by TMorita; Feb 07, 2005 at 10:09 PM.
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Old Feb 07, 2005, 10:15 PM
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Quote:
Originally Posted by TMorita
Simple.

Run the T-rex for an entire pack, then land and put your finger on the BEC chip on the ESC. If it's burning hot, then you're overloading it.

I've used linear regulators such as the LM7805 to power digital circuits, and they're normally used to regulate 8 volts down to 5 volts. Consider that:

1. A linear regulator drops N volts down to 5 volts by wasting the excess power as heat,

2. An LM7805 is in a TO-220 package which is about three times larger than the surface-mount regulators used on the Phoenix series, so the LM7805 can dissipate a lot more heat,

3. An LM7805 is typically used for regulating 8 volts down to 5 volts @ 1 amp, so it's dissipating 3 watts as heat.

4. The tiny surface-mount regulator on a CC Phoenix is regulating ~12 volts down to 5 volts @ ~2 amps, so it's trying to dissipate 14 watts

So basically, the surface-mount regulator is trying to dissipate about 4x the amount of heat in a package that's 1/3rd the size of an LM7805.

Toshi
Toshi,

I know you are very smart but you lost me and your info means quite a bit to me. Yes As I remember the ESC was hot don't know how hot though in fact I can have the bird sitting on my table with all electronics on and just playing with the controls on the TX and the ESC would get very warm. So then this is not a good setup then?

Could I invest in better controller would that solve my problem?
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