Broken coil in HD mini Camera

[lartsu]

I have Walkera Runner 250 HD mini Camera where the one of the coils is broken.

Unfortunately there is no markings to identify the inductor. Hopefully some of you can assist me to identify the broken part.

[orbanp]

Hi lartsu,

Just an idea.
Are the coils the same?
They do look from the pictures, but they could be different. You are probably in a better position to answer this question.
If they are the same, I would remove the bad one and a good one as well, and would measure the good coil.
Again, this is just by looking at the pictures.

Good luck, Peter

[james_s]

Can you identify the IC they are connected to? If so, check the datasheet and reference designs, it will probably give you an idea of values. Also it's hard to tell from the picture but is the original coil intact at all? You might be able to glue the pieces back enough to measure it.

[lartsu]

Thanks for giving me  tips.

- For me the coils seems to be the same. The size is about 3 x 3 mm.
- I tried to identify the chip next to  coils  without success.  It seems that chip next to coils has  markings ES 2L 22 K  (8 x 4 pins).
- How can I measure the coils? Is the only option to measure the coils resistance?

[Rasz]

impedance inductance (duh) (milli henry)

is the ripped off coil broken? or only solder joints let go?

what tools do you have available?

[james_s]

Resistance will tell you very little, you need a meter that can measure inductance. There are a few tricks out there if you don't have a LCR meter, it's possible to measure inductance using the capacitance range of many multimeters provided you have a known inductor to compare to since the value that the meter will display will not be calibrated to anything. You can also build a Colpitts oscillator and measure the frequency with a counter or scope. It's a very simple circuit, I once threw one together in about 5 minutes out of parts I found on the floor and it worked on the first try.

[Armadillo]

from the photo, its not very clear, but it seems like the inductor is in tack and can be re-solder back to the track. Measure the inductor to confirm that the coil is not broken and the ferrite core in place. Use ohmmeter will do. it will show very low ohm.

[lartsu]

It seems that coils wire is  broken and cannot  resolder.

I do have fluke 289 for measurements.

BTW - What does the  DC resistance means in datasheets?
e.g http://psearch.en.murata.com/inductor/result/?i_pid=LQH3NP??GR*&pid_method=begin&status=W03_049

[james_s]

It means the DC resistance

An ideal inductor would have only inductance, but nothing is ideal and in reality it will have parasitic resistance too. Think of it as a resistor in series with an ideal inductor. It mostly is used to tell you how much current you can pass through the inductor without overheating it.

[Armadillo]

BTW - What does the  DC resistance means in datasheets?

You can imagine it as a measure of definite energy waste/loss in the coil. This entity is dependent on wire size use to wound the inductor, and the size of the inductor designed for the circuit.
I reckon, if you want to try, anything in the range 5uH ~ 10uH but must SAME footprint as the original can be tried.

[lartsu]

Yep. 

I just thought the relations between the measured resistance from coil and the value from datasheet  in case of  3030/3015 size coils.  The resistance measurement shows for coil   ~1 ohm. Some of  datasheets (for 3030/3015) shows the  inductance 33 uH where the resistance is ~1 Ohm. Am I totally wrong ...?  Is this just a bad quess without clue.
https://www.elfa.se/Web/Downloads/_t/ds/74404032330_eng_tds.pdf?mime=application%2Fpdf
https://www.elfa.se/Web/Downloads/_t/ds/SRN3015_eng_tds.pdf?mime=application%2Fpdf
http://psearch.en.murata.com/inductor/product/LQH3NPN330MGR%23.html

[james_s]

If it's the same manufacture and series then you may be able to tell, but otherwise DC resistance and inductance are not directly related. The DCR is determined only by the length, cross sectional area and composition of the wire itself used to wind the coil.

[Armadillo]

unfortunately a wide range of inductors are "ALL" approximately < 1 ohm.
Because the designed current flow is related to wire coil gauge size as such DCR varies with it and the inductance varies with numbers of turns and wire gauge size also....
You can measure the pulsing rate from the microcontroller. Then guess the buck or boost design voltage and guess the design current (Irms or Isat), then the guess would be more closer. I don't think it need to be precise. [I am guessing its a buck converter flyback coil, I could be wrong]

DCR = manufacturer bragging sales speech about "Q"uality of their coil. So, don't use it in making your guess about the inductance. [I know some of you may object to my simplification here  ]

Is the inductor cheap in your country? Are there any minimum quantity or $ to obtain?

[lartsu]

The inductors are not too expensive for giving a try. What are your best guesses if I will try with some of the chips?

Do you have any clues what is the chip next to coils?  ES 2L 22 K  (8 x 4 pins).

[Armadillo]

I think is a "custom" microcontroller of sought, you can check the pulse from the pins, if its alive. But But But, the whole cam cost less then US$20, I think you are a real gamer for experiments. You will also need minimum loupe, sharp pointed soldering gun or reflow station.... Go through the process of buying the inductors and see if there are minimum conditions to buy one or few of it, then consider it.

[lartsu]

Yes, the new ones  are cheap... but as you can know most of us  doing this as hobby. 

It's "rewarding" if the gadgets are got back to alive.  I know that this doesn't save the world (and money) :-)

[Rasz]

again - what tools do you have? aka do you even have a soldering iron? hotair?
tools to fix this will be ~$30-50

inductance of this coil is not critical, its just one of the VERY low power DC/DC buck converters. You could even fish a broken hard drive from a pile of scrap and pick a random similar size coil from that, but good luck desoldering it with one ordinary soldering iron

[lartsu]

Thanks, all of you!

I do have soldering station with hot air and microscope for soldering work.

[james_s]

It's actually not too hard to desolder small SMD parts like that with a regular soldering iron. Just heat one joint and the heat conducts through the whole device and it falls off. Hot air is better though.

[Armadillo]

It's actually not too hard to desolder small SMD parts like that with a regular soldering iron. Just heat one joint and the heat conducts through the whole device and it falls off. Hot air is better though.

This is too over simplistic. You are imagining SMD means only 2 pin device, with all neighbouring components spread so far away that allow your regular soldering iron with regular fat head to contour the way its want to easily reach the pin to heat it. For 0402 device, the regular fat head generally can heat few vicinity components at the same time and accidentally remove them.

its not hard but in some situation is not easy with the regular soldering iron. But I agree with you that Hot air is better.

[james_s]

Well I'm talking about the inductors being discussed here, they are small 2-pin devices, and I've desoldered similar inductors using a standard spade tip on my soldering iron. I've also used two soldering irons to desolder larger inductors. Obviously this isn't going to apply to 208 pin TQFP parts and such.

[amyk]

I don't think that IC is a microcontroller but a PMIC. I seem to remember seeing someone else on the forum here with pictures of the same IC in a different device --- it's almost certainly a multichannel buck converter. Unfortunately Sunplus SPCA6350M documentation is almost nonexistent.

[lartsu]

One quick & easy question.

Does it make the difference if I use for test molded or shielded inductor  instead of original semi shielded? The plan is to  solder the test inductor via wrap wire.

[Armadillo]

Can't tell what you use and the resulting rf radiation. Leads should be as short as possible.
The only concern is noise on the picture, but you need to try it out to find it out.
Give it a go, learning is not to worry too much.

[Rasz]

yes, in the words of our prophet



its a non critical low voltage very low current rail, probably 1.2 or even 0.8 volts, find a suitably small coil on a junk board and bodge it in.