DIY BEC - Very Easy

by PyroMan | January 15, 2013 | (12) Posted in Projects

I am currently building a balsa airplane that will be powered by a glow engine. I need a lightweight battery pack to power my receiver and servos. I have plenty of lightweight LiPo batteries from my electrics so I plan to use those with a BEC. Instead of buying a BEC, I made my own in less than 15 minutes! 


To make a simple BEC like mine, you only need three electronic components: 

- a 7805 voltage regulator

- two 47uF capacitors 


Along with the electronic components you will need a way of plugging the BEC into your receiver - I used a servo lead from a destroyed servo - and a connector for your battery - I used a JST connector because that is what my lipos have on them. One other part you probably want will be a heat sink. Although this isn't necessary to make the BEC work, it does help cool the BEC if you are pulling a lot of current. 


To solder it up, just follow the schematic below. This BEC takes the supplied voltage and drops it down to a constant 5v for the receiver and servos.  Like I said this is super easy and works well. 




If you would like to see my other projects, be sure to check out my website www.backroomworkdesk.com






 







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COMMENTS

RedBaron1 on January 16, 2013
Looks good, but technically isn't this just a voltage regulator, not a BEC? The battery has not been eliminated from the glow-power system; although it allows the use of the higher voltage Li-Poly battery.

Just a clarification for those who may not be familiar with glow-power set ups (I remember back when....glow systems were the norm and electric was rare... man, am I that old already?)
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PyroMan on January 16, 2013
In my case, yes, I guess it is just a voltage regulator. I think, however, if this was used on an electric plane then it would be considered a BEC. The reason is because if your ESC didn't have a built in BEC you could use this device to eliminate the need for an extra battery pack designated for the receiver/servos. Hence the name "battery eliminating circuit"

Now, I could be mistaken. I'm just beginning to learn all of this electronic stuff. So, anyone feel free to correct me if I am wrong.
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tramsgar on January 16, 2013
This would be a linear what-we-call-BEC =). You could perhaps include a simple battery saver using a zener diode.
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casehatter on January 17, 2013
good point, and now we have a safe in line voltage regulator or lbec or it works man. Thanks guys not everyone likes a forum.
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rogerjiangcf on January 22, 2013
This is a great idea but it isn't suitable or safe for any planes that uses a 3s/4s lipo since the LM7805 need to regular approximately 7v down for 3 s and 11v down for the 4s setup and that will overheat the IC chip for sure. It's chip has a overheating protection circuit inside so you have to say bye bye to your lovely plane when the protection circuit kicks in. In addition, this IC chip is only able to give out 1A current max so it's only recommended to use in models like the old fogey. Since the esc you brought should already have BEC, why you want to spend more money on this. Using this homemade bec for receiver and servo testing is only place that i can think of that's useful.
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PyroMan on January 22, 2013
Although I personally haven't tried it out with a 4s, I would agree it probably wouldn't be too 'safe' . . . for your airplane that is. Now in the video I did use a 3s and I didn't notice any problem when running just two servos. As a test I did six servos moving simultaneously using a 3s and it did get a little warm, but it quickly cooled down once I let the servos rest.

The model I will be using it on, and probably the most practical type of plane to use it on, will be a small glow engine. The plane is a 36" WS airplane (Minnie Mambo) powered by a Cox .049 and it will only have two servos on it. So I don't have an ESC, but I need a lightweight way of powering the receiver. A NiMH pack is too heavy and a small LiFe battery is a little pricey. This seems to be my best option for what I am doing.
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AERODROME on February 7, 2015
SOME OF THE ISSUES HAVE BEEN COVERED THE 7805 IS A 5 VOLT ONE AMP REGULATOR. MOST ESC'S HAVE AT LEAST A 2 AMP BEC. A TWO CELL LIPO WOULD BE THE BEST CHOICE FOR THE BATTERY. A 7806 WOULD HAVE BEEN THE BEST CHOICE FOR THE CHIP SERVOS WOULD RUN A LITTLE QUICKER AND 6 VOLTS ARE SAFE. IF USING JUST TWO SMALL SERVOS YOU CAN GET AWAY WITH THIS.
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DIY BEC - Very Easy