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Old Aug 17, 2012, 06:25 PM
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United States, NM, Las Cruces
Joined Jul 2012
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Possible Power Supply Problems

I am running a PZ P47D with a Power 25 1250KV and an Eflite 60A pro esc. I recently hooked up the tm1000 module in conjunction with my DX8 transmitter. The plane has 6 digital servos. Now that the system is on the table, here is my problem. Recently I have noticed that my tm1000 likes to turn off and come back on at weird times, sometimes not at all until another battery is inserted. To be sure I do check batteries with my electrifly meter before every flight and the batteries are full. The telem module has been recording a very wide range V drop to the Rx. High is usually around 5.6v and low around 3.6 which seems low to me. So I ask, what do you think is the problem? A short in the wires somewhere? Maybe to much going on for the esc to handle? It is only rated at 2.5A for the bec in the esc. It was flying fine for about a dozen times. Do you all think a seperate bec is in order? A Rx pack? Or just bad luck and got a bad signal? The plane was a total loss. If you do recommend a new piece of equipment, let me know what has been working for you! Thanks
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Old Aug 17, 2012, 06:57 PM
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Toronto Canada
Joined Dec 2002
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You didn't state whether you are using 2 or 3 cells.

For fun, let's say 3 cells or 11.1V

That means that the BEC has to drop 11.1 -5 = 6.1V.

If you are sometimes pulling max BEC current or 2.5A (easy to do with 6 servos), that is about 15W which the regulator in the BEC must dissipate.

There is an old rule of thumb which I used to use. If an individual component of any kind dissipates more than 5W it needs a large heatsink.

In your case you likely need an external BEC. Your BEC is likely shutting down from thermal overload or your receiver is browning out.

I'm certain others on this thread will help you choose one.
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Old Aug 17, 2012, 09:16 PM
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Australia, QLD, Twin Waters
Joined Apr 2011
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Hi Guys from Australia. I have a BEC connected to my receiver. do i cut the red wire from the ESC that connects into the throttle when i install the BEC?. Alex
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Old Aug 17, 2012, 10:00 PM
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Chattanooga, Tennessee, United States
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Yes.....but better yet, connect a short servo lead between ESC and Rx and cut the red wire on that... then you can use your unmodified ESC on future planes.
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Old Aug 18, 2012, 05:12 PM
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United States, NM, Las Cruces
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I run it 3s 2200 30C and 4s 2200 40C
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Old Aug 19, 2012, 02:56 AM
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Letchworth, Great Britain (UK)
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It's unlikely to be a "short" in the wires, but it could be a poor connection (solder joint or plug) that's causing the voltage drop.

But with six digital servos I believe it's also quite possible that you're simply overloading the BEC. A lot depends on your flying style, but digitals do draw more power than analogue servos even when at rest.
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Old Aug 21, 2012, 05:59 PM
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Quote:
Originally Posted by abenn View Post
It's unlikely to be a "short" in the wires, but it could be a poor connection (solder joint or plug) that's causing the voltage drop.

But with six digital servos I believe it's also quite possible that you're simply overloading the BEC. A lot depends on your flying style, but digitals do draw more power than analogue servos even when at rest.
CC BEC and problem solved. What do they mean by "switch out the connector if you anticipate any more than 5A". I realize that servo connectors are not made for more but would one switch it out too????
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