Mikrokopter Mikrokopter BL tips

[Bartman]

In the last week I've had to expand my skills to include removing and replacing BL's from an Okto XL board and I've also been pulling and replacing SMD components from the BL's themselves. Here's a brief list of what I've come across.......

The little black resistors that are very near the mounting holes on the tops of the BL's are VERY VERY VERY prone to damage when the plastic nuts are being installed and removed. Be VERY VERY VERY careful when mounting boards or removing them because the resistors crack or get knocked off VERY VERY VERY easily. With a cracked or dislodged resistor you'll get blinking red lights instead of the usual solid red light that indicates the board is ready to go.

There are two groups of pads on the bottoms of the BL's for establishing the address or number of the motor controller in the I2c stream. By putting a solder jumper across the various pads the boards are given their identities (#1, #2, #3, etc). If too much heat is used to place the solder jumpers, the solder holding the other SMD components in the area can melt and allow the components to float off their spots. If they move far enough they won't be in position to participate in the circuitry and the BL will not function. Only use enough heat to get the solder to lay out on the pads and then stop.

With the mounting holes for the capacitors the positive points are both on the inside and the negative points are both on the outsides of the board. the inner positive holes on the XL board (not the BL although the BL holes have the same polarity and position) are hard to solder and require a lot of heat. If you've got a BL with a mystery ailment and you're absolutely sure that the components and I2c jumpers are all correct, try putting a dab of flux around the positive legs of the capacitors on the power board side of the joint and re-melt the solder. Even add a little bit of solder if the underlying pad is visible at all.

All of this is in addition to having the capacitors hot-glued to the BL's. MK and some of the dealers use a small dab of black hot glue that is insufficient for the job of holding the BL's in place. THe black hot glue is hard when dry and has little adhesive power to grip the capacitor body. I've been using clear hot glue from the crafts store and it remains soft and sticky enough to keep the capacitors from coming loose. Of course, all of this hot glue makes a bit of a mess if you ever have to replace a FET but that's a bridge I'd just as soon cross when I get there rather than let the capacitors buzz and break off from vibration.

Regarding the FET's, I've had the pleasure of removing and replacing those as well. There's a great video on youtube that shows the task being done on a first-version BL but the steps are the same. If you're going to try it I'd recommend soldering the body of the FET in place before trying to solder the legs. Place the FET on the board with tweezers then just hold it in place while heating things up. The solder will flow under the FET without much effort although it helps to leave a dab of flux under there to clean things up when you apply heat.

I've got another board to fix so I may have a few more suggestions to add. In order of heat required I'd say the positive legs of the capacitors on the power board side require the most heat and the SMD (surface mounted device) components (resistors, FET's, etc.) require the least. SOmewhere in the middle are the motor wire attachments, I2c jumpers, capacitor leg joints on the BL side of the joint, etc. the blade soldering tip that came with my iron is too big for the SMD components but the pointy tip I've got is too small for the capacitor joints.

Getting intimate with the BL's and the power boards has helped me to become a little more assured of the BL's abilities to do their jobs. I'm seeing problems caused by mechanical damage, heat damage, and poor assembly and each problem helps the "MK is just plain bad" fears to subside a little. It's what I've got so I've got to make it work at this point. Besides, they fly really well!

Good luck,
Bart

 

[Bartman]

Forgot to mention, if you're buying an Okto power board and plan to do the assembly yourself, buy the XL board as the assembly is soooooooooooooo much easier than with the standard Okto board.

 

[J.T.]

Gold mine of info..Thank you.

 

[Malaysianflyer]

Excellent info, thank you for taking the time to do this

 

[Bartman]

No problem guys, hope it helps.

Here's another little detail I came across that can spoil an otherwise good BL and power board. If you look at the bottom of the BL from the side with the capacitor holes (opposite the I2c holes), the left inner (positive) hole is very close to the two little surface mount components (resistors maybe?). It's very easy to have a little bridge of solder from the left capacitor's positive leg to the closer surface mount component. It can be cleaned up pretty quickly with some solder wick but if something like that were left unfixed I'd guess it would cause the BL to malfunction.

I'll try to keep posting things here as I come acros them. I've been doing a bunch of BL related repairs lately and I just assembled my first full Okto XL board that checked out OK so I'm feeling a bit like I've conquered the dragon.

We'll see if it flies though!

Bart

 

[jrlederer]

Bart, nice writeup. I, too, have come to many of these points you've raised through my own trial-and-error and close inspection of the boards. It is assuring to see that another has noticed the capacitors not being well-soldered causing potentially malfunctioning boards or quirky ones as the connections intermittently come undone due to vibrations during flight. I, too, ended up using craftsman-type of hot glue (the clear, actually tinted yellowish glue-type) that i bought at a local hardware store. I was very unconvinced that without the added glue, that these components would have any chance of not being immediately damaged, or at berst damaged over a duration of being used. After one of my first flights a long while back, I had a sorta hard landing where the rig tipped and I broke a single prop. After repairing the visible damage (only the prop), I went to test-fly and noticed that one motor was not engaging. I looked in MKTools and realized there was an i2c error. In fact, the motors were acting bizarre, as after the initialization tones, some motors would simply begin rotating without being so commanded, and then would begin a jerky on-off type of behavior. I thought it must be some major problem, but after removing the HexaXL board and giving it a very long and detailed inspection, I finally found that the capacitor holes that serve also to link the board to the slot in the framework of the HexaXL, was a tiny tiny bit wiggling and determined it was as a result of a cold-solder, even though I was certain (or almost) that all my solder points were done properly. I, too, added some flux and reflowed the solder joints and added a bit of fresh solder to the points in question, then continued and as a preventative measure, repeated this on all of the possible points of failure I saw. I have not yet replaced any FETs but will definitely bookmark this discussion and view your advice if and when the time comes. I'm not sure if it's the best thing to do, though it has so far worked flawlessly for me, but I also added a small bead of hot glue to much of the perimeter of the BL-Ctrl where it meets up with the framework to the PDB. I was worried, initially, that this would impact the heat-dissipation that the framework provides by distributing the temperature throughout, but fortunately it has proven effective as shown by the last 150+ flights (at least) without any issue to speak of. YMMV.

Thanks again for the great writeup.

--Jonathan

 

[Bartman]

Thanks Jonathan.

I came across another little BL gotcha (ugh!) that can potentially put an I2c error into an otherwise perfectly good power board. THe two I2c pads are pretty close together on the BL's and it's possible to over solder the I2c jumpers and cause the two pads to wick together between the BL and the power board. It's an assembly defect you wouldn't realize until you got the I2c error and you'd have to pull the boards apart to find it. To prevent this, don't oversolder the I2c jumpers, use a touch of solder above and below the board and that's it. Maybe two touches if the pads look bare.

I didn't actually have this happen but in chasing down an I2c error and pulling I2c jumpers I saw that my overuse of solder left more solder than necessary inside the overlap of the BL and power board.

If you get an I2c error, first hook up the flight control (without the power board attached) using the MKUSB jumper to power it and make sure the I2c error isn't being caused by the flight control board itself. It's normal for MKtool to tell you that BL's are missing when the power board isn't hooked up but you shouldn't be getting an I2c error from just the flight control.

If the flight control board is OK, grab the power board and apply 4S power to it. The LED's on the bottoms of the BL's should complete their self test sequence by illuminating solid red and green. if any of the reds are flashing, those Bl's with flashing red LED's are having a problem. It's possible for all the LED's to glow solid red and green and for an I2c error to still be there.

If the LED's all come on, go out, then glow solid green and red you can then try to reattach the flight control and turn the power on again. with a good flight control the good LED's on the BL's will glow green only while the bad ones will glow green with a flashing red. it's again possible for them all to glow solid green and for there still to be an I2c error.

If you just can't get any help from the BL's LEDs, you'll have to go the next step which is to pull I2c jumpers. The jumpers are the small wire pieces that go through the I2c holes on both boards holding the BL to the power board and allowing the I2c signals to reach the BL's. Start by pulling the jumper wires for BL #1, separate the end of the BL from the power board and then attach the FC to the power board, apply power and use MKtool to see if the I2c error is still there. If the error is still there, move on to BL #2, pull the jumpers, separate the end of the BL from the power board and then reattach the boards to MKtool and see if the error is there or if it's cleared. When you disconnect the bad BL jumpers, the I2c error will clear and you can go about replacing the bad BL, replacing the pulled jumpers, and putting the power board back into service.

it all sounds harder than it really is.

bart

 

[Drones4You]

Mikrokopter Bl Control Tps

Many people asked for some more details on the BL Control changing video we did some time ago.
We decided to do this little video to show some details of the BL Control BEFORE the change.

As we received many multirotors here to make the maintenance , we saw that some details are not being taken in consideration for those who are trying to assemble they copters.
All this putting they machines , investment and people in risk.

 

[Bartman]

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