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Options on Capacitor install location
#1
I have had success with using a low esr cap on the battery leads of a quad for cleaner video.  All the sources say do this where the battery leads attach to the pdb.  Can I just put the cap on any open pads of the PDB?  I would like to move it away from the battery leads for better packaging.  

What's better - putting wires on the capacitor leads and attaching at the battery tie in, or shorter leads on the cap but mounted elsewhere on the PDB?  or does it matter at all.  It seems like it should not matter electronically.
#2
In theory the best placement of the capacitor is as close to the noise source as possible which in our case will be on the escs. But if you are using just one cap, you can put it on whatever pad you want on the PDB as long as it is on one of the main pads (esc, battery etc)
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#3
Hello, I have a question, would adding 4 smaller 25v caps to each ESC be better for reducing the noise going into the 5v and 12v BECs from the battery? Or would it be better to have one big cap on the battery before it connects to the BECs?
Also, in the case of 4 smaller caps, would they're voltage protection add up to 100v (25v each) like they're micro farads add up?
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#4
If you have the room on your build, you're better to use 4 smaller caps on the ESCs so as to be as close to the source of noise as possible.  These are what I use
https://www.readymaderc.com/store/index....ts_id=6526


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#5
(07-Jun-2017, 12:25 PM)RazzMtazz Wrote: Hello, I have a question, would adding 4 smaller 25v caps to each ESC be better for reducing the noise going into the 5v and 12v BECs from the battery? Or would it be better to have one big cap on the battery before it connects to the BECs?
Also, in the case of 4 smaller caps, would they're voltage protection add up to 100v (25v each) like they're micro farads add up?

Capacitors in parallel add together, so 4 x 250uF is 1000uF.
The voltage rating of the capacitors does not as the rating applies to each individual component.
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#6
Thanks for the info, is it still benificial to add caps to my mini quad even if im getting absolutely clear video on fpv? Does it help with quad stability and PIDs to function better?
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#7
(08-Jun-2017, 09:47 PM)RazzMtazz Wrote: Thanks for the info, is it still benificial to add caps to my mini quad even if im getting absolutely clear video on fpv? Does it help with quad stability and PIDs to function better?

It won't hurt anything and might save your video camera from any voltage spikes generated by the ESCs and motors during active braking.

It has nothing to do with how the quad handles or how the PIDs should be tuned, it's only about controlling some of the incredible electrical interference that can be generated in a quad.
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#8
(08-Jun-2017, 10:05 PM)unseen Wrote: It won't hurt anything and might save your video camera from any voltage spikes generated by the ESCs and motors during active braking.

It has nothing to do with how the quad handles or how the PIDs should be tuned, it's only about controlling some of the incredible electrical interference that can be generated in a quad.

Sorry to bug you so much, was wondering if you could clarify this, i have this PDB :
http://www.aliexpress.com/item-img/QAV25...96872.html

It seems to have some sort of LC filter on it already although im not really sure if its on the 12v line or 5v line. I use the camera on the 5v line. also i use another LC filter on the 12v line between the PDB and vtx. Would adding low esr caps on the esc's still be benificial to me?

Edit: Boaterguy over at rcgroups.com says it will increase the response speed of the motors?
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#9
(09-Jun-2017, 04:20 AM)RazzMtazz Wrote: Sorry to bug you so much, was wondering if you could clarify this, i have this PDB :
http://www.aliexpress.com/item-img/QAV25...96872.html

It seems to have some sort of LC filter on it already although im not really sure if its on the 12v line or 5v line. I use the camera on the 5v line. also i use another LC filter on the 12v line between the PDB and vtx. Would adding low esr caps on the esc's still be benificial to me?

Edit: Boaterguy over at rcgroups.com says it will increase the response speed of the motors?

An LC filter removes high frequency noise from the power. It is great for getting rid of noise on your FPV video.

A simple capacitor on the ESC helps to suppress high voltage spikes that can be generated by the motor during braking.

Fitting them is entirely optional and many people fly without problems without adding low ESR capacitors to the ESCs.

I have no idea how adding them would increase the response speed of the motors and I have not seen any testing that would support that theory.
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#10
Thanks very much for clarifying the difference between the lc filter and a low esr cap Smile i think ill put some on it just to be safe Smile
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#11
(09-Jun-2017, 08:12 AM)unseen Wrote: I have no idea how adding them would increase the response speed of the motors and I have not seen any testing that would support that theory.

My brain works in strange ways, due to this my understanding that caps charge and discharge would suggest that it could only decrease throttle response? I understand that the caps might smooth the flow and by limiting back EMF should make the ESC signals less 'noisy' making for smoother throttle response which might feel more responsive?
Windless fields and smokeless builds
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#12
Hello, is it normal that the 1000f 35v cap i soldered on pdb below the xt60 socket is getting warm after 3 minutes of flight? It was not really hot but i was just cruising....
Motors are racerstars rf2205 2300 esc ms series 35a props kingkong 5-4 tri.
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#13
(04-Jul-2017, 07:32 AM)lorentz Wrote: Hello, is it normal that the 1000f 35v cap i soldered on pdb below the xt60 socket is getting warm after 3 minutes of flight? It was not really hot but i was just cruising....
Motors are racerstars rf2205 2300 esc ms series 35a props kingkong 5-4 tri.

I do not know the answer to your question but I am going to be adding a capacitor or capacitors to my mini quad very soon. I haven't decided yet if I want to solder a bigger cap to the main battery pads/leads or if I want to use 4 smaller caps soldered to each ESCs power and ground. My mini quads configuration is a very similar setup to your mini quad. I have Racerstar BR2205 2300kV motors and Racerstar MS30A v2 ESCs. Since a month or so has passed since your post, I was wondering what happened or didn't happen with your capacitor. Meaning; does it continue to work as well as it did on day 1? Did the capacitor blow up or potentially cause some other issue? I am also curious about what the specs are on the cap that you are using. More specifically what is the voltage rating, micro-farad rating, and is it a Low ESR capacitor or a normal capacitor?
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#14
I'm using low ESR 4*470uf 25v rubycon on one and 4*470uf 25v Panasonic FM on another build. I prefer the panasonic capacitors as they are a bit smaller
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#15
Obviously it won't help now you've purchased the camera & VTx however next time you are sourcing parts, choose a camera and VTx that'll run off battery voltage. Doing so would most likely mean (if you're using decent ESC's of course) that any voltage spike caused by active breaking will still be within the operating range of your hardware.
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