Mikrokopter Missing Cap on BL-Ctrl V2.0 ??

MikroJ

Member
Hello, Just looking around at my BL-Ctrl V2.0's the #6 only has one cap, where as every other one has two?? Im running the MK3538 motors..... I bought this pre built and would like to know if this is right......
Cheers
 

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FOX222

Member
Hello, Just looking around at my BL-Ctrl V2.0's the #6 only has one cap, where as every other one has two?? Im running the MK3538 motors..... I bought this pre built and would like to know if this is right......
Cheers

MikroJ, What is soldered to these holes I have circled? Is there a cap underneath?
 

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Bartman

Welcome to MultiRotorForums.com!!
fox,
the BL to the left has a cap in that position above the board. why would someone drop it underneath in the area you circled? it's tough to see but it doesn't look like there is one under there.
can someone please put into layman's terms what the capacitors do for the BL's and why it's preferable to have two caps per BL for larger motors? i suspect it has something to do with providing some degree of voltage stabilization (like a mini onboard reserve) but i suspect someone here can explain it much better.
thanks,
bart
 

FOX222

Member
fox,
the BL to the left has a cap in that position above the board. why would someone drop it underneath in the area you circled?
bart

I am not sure why people do a lot of things they do, but it looks to me like something is soldered there.

MikroJ,
It's hard to tell from the picture but it looks like there are only 3 caps at all the power taps. This is ok because they all tie to the power bus anyway. So what you really have is 3 caps shared between the 2 bl's. The purpose of the caps is to buffer sudden power surges so higher current systems need more (or bigger) caps to handle the surge. The closer the cap is to the esc the better due to resistance so the ecs with 2 caps soldered to the mains would in theory show a little less of a drop but you would be hard pressed to measure it.

John
 

MikroJ

Member
no cap underneath , It looks like it has had one, due to small "legs" and solder underneath, it looks like its been bumped/snapped off :mad:

Looking back at pictures before it was sent to me it was like this, so I know it wasn't myself, during postage or putting back together .......

Each bl has 2 as you can see in picture attached.

So question is and may have been already answered, but to confirm can it still safely operate like this? I went to order one from "US site" its $3 but $40 to get one over!!!

any advise as to what cap I need to find : ie generic or is it a MK special???
 

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Crash

Defies Psychics
The stock caps aren't special unless H&I put some magic juice into them.:rolleyes:

I thought they were about 44 cents each. USD.

The good ones are $2 or $3 each as I recall. They are low ESR and I probably have the part number somewhere.

Either way, glue them down somehow.
 

Bartman

Welcome to MultiRotorForums.com!!
grab whatever identifying marks you can off the ones you have and google the part numbers to see what's available. i seriously doubt they're anything specially made for Mikrokopter.
have you been operating it like this for long? i think you're fine in the short term but it depends on what the loads are that you're carrying and how aggressively you're flying it.
i'm sure fox can answer better but that's my take. :)
bart
 

FOX222

Member
MikroJ,
You can use about any make as there is not that much difference in them. What you need is a 330 microfarad 25 volt electrolytic capacitor. You should be able to find them at any electronics supplier.
As for being safe to fly....probably if you not are carrying a heavy load with it.

John
 

MikroJ

Member
I thought they were about 44 cents each. USD.
$3 from MK us site plus $40 postage?? um no thanks....

Either way, glue them down somehow
is hot glue ok to use? anyone got pics of how they have done it ? or what is best product to use....

have you been operating it like this for long?
Haven't had it in the air yet, but previous owner not too sure ......

As for being safe to fly....probably if you not are carrying a heavy load with it
Not going to strap anything to it just yet, only a small fpv type camera and 1000mAh lipo with transmitter.

So if I manage to find a cap am I right in saying the NEG side faces the outside of the MK on that particular Bl Ctrl?

I just found these would the be compatible ? http://www.galigear.com.au/capacitors/330uF-Electrolytic-Capacitors-25V

Thanks , Jim
 
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MikroJ

Member
Thanks guys , got 5 for 11 cents each and free postage......Dont know how they make money off that considering the express postage would have cost well over $5?? anyway not for me to worry I got what I needed and fixed the missing cap !! Now waiting for controller to arrive!!
 


Both a conversation with the guys at quadrocopter.us, and now Ziggy confirm that something about the Heavy Lifters is causing the caps to vibrate and snap off. The recommended "fix" is to hot glue the caps down.

I stare at my caps and try to imagine the vibration it would take to make them snap off, and then I drift off to a place where all my brain cells shut down. Then, I remember the History Channel show I saw about Nicola Tesla, who invented some sort of resonance machine (Earthquake Machine) with which he claimed he could bring down buildings. The story (folklore) was told of how he attached his machine to a half-built steel building:

"He put his little vibrator in his coat-pocket and went out to hunt a half-erected steel building. Down in the Wall Street district, he found one: ten stories of steel framework without a brick or a stone laid around it. He clamped the vibrator to one of the beams, and fussed with the adjustment until he got it.

Tesla said finally the structure began to creak and weave and the steel-workers came to the ground panic-stricken, believing that there had been an earthquake. Police were called out. Tesla put the vibrator in his pocket and went away. Ten minutes more and he could have laid the building in the street. And, with the same vibrator he could have dropped the Brooklyn Bridge into the East River in less than an hour."

I digress. The fact that this vibration can snap off the caps is fascinating and alarming at the same time.
 

Buzzed

Member
I know that it would add a bit of weight but I'm wondering the the resonance would be passed from the airframe to the BLs if you used those rubber isolation dampers under the PDB.
 

Bartman

Welcome to MultiRotorForums.com!!
usually the quick fix when things begin to resonate is to adjust weight to make different components have different resonant frequencies. gluing the caps might help but the issue will just move on to the next most vulnerable component, motor wires solder points maybe?
 

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