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UBEC vs Step-Down Voltage Regulator - Best Choice for Camera and TX?

kah00na

Senior Member
#1
I'm wanting to run a quad off a 4S battery but need 12 volts for the TX and camera. What is the difference between using a UBEC vs Step-Down Voltage Regulator? Does one provide clean power while the other doesn't?

UBEC Pros:
UBEC can (most of the time) have a higher output mA.

Step Down Pros:
Voltage regulator is lighter
Generally cheaper

I'm specifically looking at some like these:
18788(2).jpg


0j4327.600.jpg
 

Epitaph

Ebil Filleh Pega-Bat ^.^
Mentor
#2
In most cases, a voltage regulator simply burns off the excess volts, in the case of a 4S, up to 4.8V fully charged to give you those 12V you are looking for. This on one hand is just waste of power, and on the other hand produces heat. A UBEC on the other hand converts the voltage by "rule of transformer" basically (although it's not how they actually do it, rather it uses a switch) which is the power going in is equal to the power going out, with no loss of power through heat. In esscence it is more efficient, allowing the battery to last longer and not producing heat hardly.
 

FinalGlideAus

terrorizing squirrels
#3
Ahh no. The regulator pictured above is a switching regulator. Linear regulators do as you say.

kah00na, the UBEC's you are talking about are just another form of regulator so they are the same. The only difference is some are the switching type and some are the linear type. The switching type is the best but is noisy so can produce lines on your camera image so may need a filter added onto the power line. You just need to find one to suit your needs. The UBEC you have pictured will produce 4.5a where as the Pololu you have pictured will produce more like 500ma (I don't know which one it is). There are plenty more Pololu regs to choose from that have a higher amperage output. Just find out how much you need and choose a reg to suit.

Also, check the specs of the VTX you are running. The immersion vtx for example has its own inbuilt reg and will take up to 4s and also has another reg that spits out filtered 5v for the board camera. I use 12v cameras so I run the vtx off 4s and then put a 12v step up reg off the vtx 5v power supply to run the board cam.
 
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joshuabardwell

Senior Member
Mentor
#4
One thing you should do is avoid the use of the term UBEC and SBEC, but use "switching" vs. "linear" regulator. I only say that because I have heard UBEC and SBEC used interchangeably, even on vendors' product pages, so I'm never really sure which one definitively means which.

One disadvantage of a switching regulator, that I haven't heard mentioned, is that their constant on/off pulsing is more likely to cause noise that may affect e.g. an FPV video system. This is, ultimately, a solvable problem, and the increased efficiency is probably worth it.
 

Cyberdactyl

Misfit Multirotor Monkey
#5
To avoid junk in my FPV image, I have been carrying a small 2S 1000mAh to power my vid cam and VTx. It was a pleasant surprise to learn the PZ040 runs fine off of 2S.
 

joshuabardwell

Senior Member
Mentor
#6
To avoid junk in my FPV image, I have been carrying a small 2S 1000mAh to power my vid cam and VTx. It was a pleasant surprise to learn the PZ040 runs fine off of 2S.
If you have spare cargo capacity, this is a fine choice. The down-side is that you are probably wasting weight on battery capacity you're not using. When you land, and the video battery still is at half-capacity, that's 500 mAh you could have used for flying. Whether that matters or not is up to the pilot. A simple filter should solve interference issues and allow flying off a single pack if that's what's desired.
 

stay-fun

Helicopter addict
#7
If you have spare cargo capacity, this is a fine choice. The down-side is that you are probably wasting weight on battery capacity you're not using. When you land, and the video battery still is at half-capacity, that's 500 mAh you could have used for flying. Whether that matters or not is up to the pilot. A simple filter should solve interference issues and allow flying off a single pack if that's what's desired.
True, so to find out if it's worth it, you should measure the weight of a 500 mAh 2s battery (which by the way, would be similar to 250 mAh 4s, if you want to count it as flight mAh) and compare this to the weight of a voltage regulator.

In the end, I think it's not worth the hassle and I would personally go with Cyberdactyl's approach. But everyone is free to take his/her own solution, as long as it works :)
 

joshuabardwell

Senior Member
Mentor
#8
This 5 amp switching BEC weighs 18 grams. It has an in-built filter to prevent introducing switching noise to the system.

This 500 mAh 2S battery weighs 32 grams.

Of course, this is moot, since OP is using a 12v camera, and their system can't run off a 2S (unless you were to use a step-up converter).
 

Cyberdactyl

Misfit Multirotor Monkey
#9
If you have spare cargo capacity, this is a fine choice. The down-side is that you are probably wasting weight on battery capacity you're not using. When you land, and the video battery still is at half-capacity, that's 500 mAh you could have used for flying. Whether that matters or not is up to the pilot. A simple filter should solve interference issues and allow flying off a single pack if that's what's desired.
You're right, it is around 80g extra weight over using a filter, UBEC or step down. And I won't have the luxury of doing that with my mini quad I'm building. But on my tri and hex, it's just a convenient and easy method.
 

Epitaph

Ebil Filleh Pega-Bat ^.^
Mentor
#10
Bruce on RCModelReviews made a video showing how to change a 5V BEC into whatever voltage output you needed specifically for a camera... I can't remember if it was that BEC, but I know it was an HK one, and Bruce is a perfectionist when it comes to noise and such...