Thread Tools
Dec 11, 2019, 01:55 PM
Waiting for the next clear day
Thread OP
Discussion

Do I need a seperate BEC?


I'm putting a Quad together with these components:
4 in1 ESC
VTX
Receiver/Controller combo

The ESC doesn't have a BEC (annoying), but the VTX has a 5v out that typically powers the camera. There are no specs on the output other than it's 5v. Do you think it would be powerfull enough to power the flight controller/reciever, and the camera? I'd hate to break up the really nice ESC/VTX/FC+Reciever cube with an extra BEC hanging out there.
Sign up now
to remove ads between posts
Dec 11, 2019, 03:48 PM
Registered User
The output on the VTX is 5V 1A(1000ma) max. Your combo FC/Rec board draws 200ma. I suspect your camera will be around that also, but the specs on your camera will tell you what that is. I like to be no more that 80% of whatever so I would look at it like it will only supply 800ma max. I just made up 80%, but I like a cushion. I would look at it like as long as the current draw of the FC/Rec + camera is under 800ma, you should be OK. Also the power is switchable on the VTX. Just make sure to switch so it supplies more current that you actually need.
Dec 11, 2019, 06:16 PM
Waiting for the next clear day
Thread OP
That begs the question: How do I know that the max current rating for that 5v source on the vtx is 1A?
Thanks for the reply.

Tony
Last edited by amagalla; Dec 11, 2019 at 06:59 PM.
Dec 12, 2019, 01:18 AM
Physics, or is it fizzix?
flyandride's Avatar
You could test the electronics on the bench and see if it would work together. Powering everything off the vtx would be a hassle because that vtx would always have to be on. I like to turn it off at times, like when working on a quad.
You could find a 4 in 1 with BEC which is what I do. Or a small 5V BEC.
I've used the XSRF40 on quads but took them out and moved them to LOS gliders. Although it was a good idea by Frsky, the board did not have enough uarts. The ports tab in Betaflight will show a port that has not been broken out, in other words, you can't use it. I had to do some remapping to get a gps working. So there was no way to have gps and smart audio. If you haven't bought that board yet, I would suggest looking at others. I wish Frsky would come out with a newer version.
Dec 12, 2019, 10:30 AM
Registered User
Specs on VTX tell you the power levels for the 5VDC. You have to read these specs when making any decisions on what you are trying to do.
Dec 13, 2019, 02:24 AM
Waiting for the next clear day
Thread OP
Quote:
Originally Posted by flyandride
You could test the electronics on the bench and see if it would work together. Powering everything off the vtx would be a hassle because that vtx would always have to be on. I like to turn it off at times, like when working on a quad.
You could find a 4 in 1 with BEC which is what I do. Or a small 5V BEC.
I've used the XSRF40 on quads but took them out and moved them to LOS gliders. Although it was a good idea by Frsky, the board did not have enough uarts. The ports tab in Betaflight will show a port that has not been broken out, in other words, you can't use it. I had to do some remapping to get a gps working. So there was no way to have gps and smart audio. If you haven't bought that board yet, I would suggest looking at others. I wish Frsky would come out with a newer version.
The URAT shown in Betaflight is actually broken out. It's just tiny and hard to solder onto. It's right behind the Sbus port. It's super small. I've connected my smart audio to it. I'm not interested in the GPS, so no big deal there.
Dec 13, 2019, 02:27 AM
Waiting for the next clear day
Thread OP
Quote:
Originally Posted by macksupersnow
Specs on VTX tell you the power levels for the 5VDC. You have to read these specs when making any decisions on what you are trying to do.
I've read the specs for the board backwards and forwards. I can't find anything on the 5V output. I know that the transmitter power is adjustable and that goes all the way up to 1 watt. But that has nothing to do with the 5V output. I hope you're right, but I can't find it. Where are you seeing the 1amp max on the 5V output?

Tony
Dec 13, 2019, 04:28 AM
Registered User
Quote:
Originally Posted by amagalla
I've read the specs for the board backwards and forwards. I can't find anything on the 5V output. I know that the transmitter power is adjustable and that goes all the way up to 1 watt. But that has nothing to do with the 5V output. I hope you're right, but I can't find it. Where are you seeing the 1amp max on the 5V output?

Tony
You are right, it does not actually say anywhere that it's a 1a 5v Bec in that vtx, but it's an educated guess. Just about all vtxs will use about the same becs, usually 0.5 or 1a rated.

Since its a larger (relativly) vtx , and akk are of decent reliability, it's safe to assume that it's 1A. If it was larger (2A) they would advertise that... and 0.5a - I don't think akk would use that on this size, but I might be thinking too highly of them
Dec 13, 2019, 12:31 PM
Registered User
You are right, It does not say how much power the 5V puts out. I got confused because it is right below the 5V. If it was me and to be safe, I would get a separate BEC. You would probably be OK with the supplied one, but who knows.
Dec 13, 2019, 11:22 PM
Wake up, feel pulse, be happy!
Piece's Avatar
I wouldn't choose to power anything off the VTX except the camera. You're adding extra load to a critical system, and that extra load is your FC, which is an even more critical system.

A standalone 5V 2A regulator weighs less than a potato chip, and costs about as much as a bag of chips.
Latest blog entry: Jeti ESC resto-mod
Dec 15, 2019, 08:41 PM
Are we not men? We are DEVO!
xanuser's Avatar
VTX is one of the first things to have an issue electronics wise.
I would never trust a VTX to power anything other than camera or leds.
Dec 16, 2019, 01:09 PM
Registered User
While you probably can, I would not power anything but the camera from the vtx. I would suggest getting a 5v step-down regulator or similar, but its not nessesary. You could just power the FC from the balance plug on the battery, tap into 2 cells (6-8.4v) from the balance plug. The xsrf40 has an operating range of 4.0-10v, should be good to go.
Last edited by blazenglory; Dec 16, 2019 at 01:20 PM.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Can I disarm the bec on my esc so I can use seperate battery for RX? farmerjack61 Power Systems 19 Mar 25, 2019 01:36 PM
Question Do I need a BEC with this ESC? SkyHigh6 FPV Equipment 3 Feb 18, 2016 08:36 PM
Discussion SBACH .60 Power Setup & Do I need a BEC? FolsomFlyer 3D Flying 1 Jan 31, 2016 03:26 PM
Question Do I need a BEC for my TS832 transmitter Cinetography Multirotor Drone Electronics 1 Nov 04, 2015 01:18 AM
Discussion Do I need a seperate BEC on Omega?? travis75 Electric Sailplanes 4 May 09, 2007 07:23 AM