FPV and UBEC interference

H

HDtallrider

Well-Known Member
Hi all! Just got back in town and started back to work on my universal / detachable / transferrable FCB/FPV/GPS unit. When I bench tested the FPV setup I noticed some electrical/ static interference. I finally nailed it down to the UBEC. I changed it to another brand and had a similar result. They were both switching type with the ferrite rings. I then changed to a linear, non switching BEC and the problem went away. I have 2 questions. Why are so many of the BEC's switching ( inherently "noisy") and could these be the cause of some of the control and video problems on many of the posts?
 
Hard to beat DC-DC linear regulators when it comes to smooth and clean, flat DC output, the only thing needed is the IC and a couple of caps (which are basically for voltage stability). Quite cheap to make. They are inefficient though as they simply burn off/convert the differnce between input and output voltage to heat. As an example say you used a 4s battery and wanted 5V out. 14 - 5V = 9V, more of the voltage is being converted to heat than is actually being used, a good heat sink and air flow is a must.


Switching regulators are much more complicated and have many components (transistors, diodes , inductors etc.) along with the actual switching on/off introduces noise that must be dealt with To get a flat signal requires more components and feedback circuitry. Switching power supplies are very efficient though, and do run cool.
 
Thanks for the explanation. I think I get why they are used, now. The first one I used was a no name chinese . It was pitiful. The second one was a Turnigy. It was better so I added a barrel ferrite magnet in front of the ferrite ring. That cleared up the interference but it now weighs almost as much as a motor! The linear one was perfect. It has a finned heat sink. I didn't run it long enough to generate any heat. I will purchase a couple of top quality SBEC's with better circuitry. You get what you pay for. Back to the 2nd part of my question. Do you think these could be a contributor to some of the control and video problems members have been having? Maybe I'm not as bad a pilot as I think......... All along it's been those darn cheapo SBEC's!!!!
 
Well if you've noticed with ESCs with linear BECs you can plug all 4 in. But with the SBEC ESCs folks usually pull the power wire out of the connector on all but one otherwise it's trouble in paradise.
 
I was referring to stand alone UBEC's. Some of the control and video problems posted just strike me as electrical interference. A number of videos on line show wires braided, extra ferrite rings, metal shielding etc. all to reduce interference. I have only been in this hobby a few months. The first post I sent to the forum was about learning the hard way when purchasing cheap as opposed to quality components. Apparently I'm a slow learner:rolleyes: Thanks for your wisdom. I'm gonna go blow my budget on some good stuff......... LOL
 
Hey, holtneil. Thanks for the video. It looks like an outboard/homemade version of the circuitry that Jackson described that is already in the better UBEC's like Castle, for example. Space and weight are a problem that I have for all my builds. I'm going to save up my pennies until I can buy the good stuff. No more cheapo junk stuff. I swear. This time I really mean it! :p Buying cheap parts has always, without fail, cost me more in the long run. Keep your eye on the classifieds. I am going to list all my cheapo stuff and sell it for the cost of shipping. I am DONE:mad:
 
Funny you sent that quote. I just bought a castle UBEC and it is within $1.00 of being twice the cost of the Turnigy, AND, it is within 1 gram of being 1/2 the weight! Actually it's 1/5th the weight of the Turnigy after you add the ferrite barrel the Turnigy needs to stop the interference! I'm learning........:cool:
 
Hi HDtallrider, I used Castle Becs and ESCs on all my big Helis ,they are spot on, I will try their ESC pack on the next quad I build , Most don't use them as the price puts you off but are well worth the extra $
 
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