FPV and UBEC interference

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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?
 
Jackson

Jackson

USA member at large
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.
 
H

HDtallrider

Well-Known Member
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!!!!
 
Jackson

Jackson

USA member at large
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.
 
H

HDtallrider

Well-Known Member
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
 
H

HDtallrider

Well-Known Member
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:
 
holtneil

holtneil

Well-Known Member
Moderator
HI thats very true the saying is buy cheap buy twice , and it does work out that way :rolleyes:
 
H

HDtallrider

Well-Known Member
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:
 
holtneil

holtneil

Well-Known Member
Moderator
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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