Filtered power source... - RC Groups
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May 26, 2009, 04:44 AM
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Filtered power source...


I haven't come across an answer to this question in the past couple of days, so I'm hoping someone can point me in the right direction. I'm considering using a large 3s battery for motor and fpv power. I understand that it is possible to filter power, but I don't know what is needed. Is a filtered power source as good as a dedicated FPV battery?

Thanks,

TL
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May 26, 2009, 05:07 AM
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No, but maybe your system will be interference free. Try it out with a single power source first.

Jon
May 26, 2009, 02:12 PM
Registered User
Here's my solution: start at post #69 Use the filter in addition to switching regulators like these: AnyVolt micro for both your video TX and your camera. You can also ask Sassen, he uses a single flight battery as well. Here is one of my sample videos: here
May 26, 2009, 02:17 PM
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trappy's Avatar
There is a 2 or 3A filtered power supply by IntelligentFlight - you can buy it off their website. It's a bit large, but I powered all my FPV gear off the main 3S battery without any heat noticeable. There is also a $10 linear 12V (clean) 5V step-down PSU, not sure if it's filtered, I use a dedicated flight battery on that plane.
May 26, 2009, 03:01 PM
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TL,

If you plan on buying a 2.4GHz audio/video Tx, just buy ours, that comes full prepped for single battery duty and does not care what else is sucking power from the main battery.

ImmersionRC 500mW 2.4GHz transmitter
http://www.immersionrc.com/datasheet...05_09_2008.pdf

Cheers,

Sander.
May 26, 2009, 03:05 PM
Registered User
It's entirely possible to use the same power source... All it takes is a few capacitors to filter the power supply, and remove the interference. I don't remember off hand the exact capacitors you need, but I was considering doing the same thing... there was a post a while ago about what caps you'd need to wire in to make it interference free. It's not a hard thing to do, just have to get the right caps (caps are cheap too).

As recommended above, I'd try it and see what kind of interference you get, then think about adding some caps.
May 26, 2009, 03:09 PM
Registered User
Quote:
Originally Posted by hurleybt
It's entirely possible to use the same power source... All it takes is a few capacitors to filter the power supply, and remove the interference. I don't remember off hand the exact capacitors you need, but I was considering doing the same thing... there was a post a while ago about what caps you'd need to wire in to make it interference free. It's not a hard thing to do, just have to get the right caps (caps are cheap too).

As recommended above, I'd try it and see what kind of interference you get, then think about adding some caps.
I use capacitors on my power line to the video Tx. See this post:

https://www.rcgroups.com/forums/show...&postcount=130
May 26, 2009, 03:11 PM
Registered User
Quote:
Originally Posted by Reckless Bill
I use capacitors on my power line to the video Tx. See this post:

https://www.rcgroups.com/forums/show...&postcount=130
thanks bill, i was just in the process of searching for that post!!!

fyi... http://www.digikey.com is a good, cheap place to buy caps, if you can't find what you're looking for locally.
May 26, 2009, 04:37 PM
Registered User
I use a texas instruments PT5401 for 12v. It steps up the voltage from the 2S main pack to 12v and is capable of putting out 1A at 12V.
May 26, 2009, 04:43 PM
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Quote:
It's entirely possible to use the same power source... All it takes is a few capacitors to filter the power supply, and remove the interference.
Not quite, it takes some (one, two or more stages) LC filtering to properly get rid of all the nasty voltage spikes caused by the ESC as that subsequently provides power to each of the three poles of a brushless motor. If not you'll be welcomed by lines and/or noise in your video. But don't take my word for it, I'm just an electronics engineer, what do I know?

Cheers,

Sander.
May 26, 2009, 04:53 PM
Registered User
Sander,

I have already gotten my hands on a 900/500 setup. I'm starting to wish that I had gotten a 2.4 system, but it should be easy to switch out components as I go in the future. I have two 3s 900mAh batteries for the onboard Tx. I will try both ways - running off of the same and separate batteries. Once I test both, I'll decide whether I need to run one or two batteries and whether I should add capacitors and such.

Thanks,

TL
May 26, 2009, 05:00 PM
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TL,

Running everything off of the main flight pack without some LC (inductor - capacitor) filtering on the Tx/camera will surely give you lines and noise in the video. So you're better off using the seperate battery, do make sure you keep a very close eye on the status of that battery though, if it goes flat in flight you're basically flying blind.

Cheers,

Sander.
May 26, 2009, 05:04 PM
Suspended Account
Ps. this is a configuration that's sufficient for most 12V cameras and will allow you to run it from the main flightpack. The inductor can be anywhere between 470uH to 1mH with a rated current about 2x the current the camera draws to prevent it from having a too large voltage drop across it.



Cheers,

Sander.
May 26, 2009, 05:13 PM
Suspended Account
Pps. for powering the Tx (5V types) I'd whip up something like this, the inductor again needs to be able to handle 2x the current and the 7805 regulator needs to be properly cooled to be able to dissipate the heat it generates when regulating the battery voltage down to 5V away. If needed multiple stages of LC filtering can be used to further reduce the voltage spiking and noise generated by the ESC. Just add another stage if one isn't sufficient, obviously an oscilloscope is a handy tool in determining how much residual 'noise' is still present.



Cheers,

Sander.
May 26, 2009, 05:23 PM
Registered User
Thanks sander. I am NOT an electronics engineer, so I have a couple questions. What effect does the inductor have? Does it simply stabilize the current / voltage going through the "camera side" of the circuit? If so, is this because of the magnetic field it produces? Will this pose a danger to other components on the plane (i.e. servos) Also, I can simply use an electrolytic capacitor with the ratings described in your post above?
Last edited by hurleybt; May 26, 2009 at 05:49 PM.


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