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Jul 22, 2007, 09:57 AM
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Mikrokopter / UAVP / quadrocopter / quadrotor build

Well I finally have all the parts for the Mikrokopter controler and serial programming interface. And I should be getting motors and ESCs this week. So time to start building. And as promised a build thread....

I decided to start very carefully: I put together the serial programming interface. Simple little PCB and no really small parts And of course that posed no problems.

And then someone pointed me to a diagram in the UAVP manual which might be the solution to interfacing the Spektrum AR7000, which has no combined PPM channels, to the MikroKopter controler, which only accepts a single multiplexed PPM channel as input. The UAVP actually multiplexes only the uneven channels, calculates the pulswidth for the even channels. So, I amended the diagram to allow for all 8 channels to be input. Final product looks a bit sloppy but it works like a charm. It is connected to the RX with 3 servo leads, one of which connects to the 5V, GND, and 1 signal in, at the side of the new circuit. For the other channels I just use 2 servo cables at the circuit end, and connect each of the wires to a different channel at the Rx end. The connnection from circuit to controler requires only 1 wire.

Parts list for the PWM to PPM multiplexer:
* 8x 1N4148 diodes
* 2x 4.7 KOhm resistor
* 1x 1 KOhm resistor
* 1x BC548B (or similar) transistor
* wires and connectors of your liking to connect to Rx and flight controler.

Now of course I have to gather all my courage to start on those REALY SMALL parts for the MK controler.....
Last edited by Arthur P.; Nov 22, 2007 at 03:22 PM.
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Jul 22, 2007, 11:49 AM
Yes, right there.
SpleenRippa's Avatar
Cool! Good luck! Will be quite the vehicle when finished.
Jul 22, 2007, 06:44 PM
Registered User
After an evening of soldering I have an almost completed microcontroler board. And it does get easier with practice with these very small parts.\

I did lose 1 or 2 pads due to reheating to remove some excess solder. But they are for the gyro-amplifier resistors. If I-m lucky I won't need these particular pads. If not, there is always some thin jumper wire... So nothing particularly worrisome.

A few tips though:

1) It could be an idea to expand the Reichelt parts list with two optional parts:
--- De-soldering floss or whatever it's called in the US. You wan that in house when you need it. And if you haven't done much SMD soldering, you'll need it.
--- A lamp with magnifying glass. I actually came accross one yesterday when shopping for the missing 7805 regulator. And it has proven its worth. Only cost about 35 USD. Round fluorescent lamp with a larger 3 diopter magnifying glass and a small 10 diopter lens. And if you close the lid it looks like a simpel but reasonably stylish normal desk lamp.

2) NEVER pre-solder all pads for capacitators, resistors, LEDs or other SMD components.
--- The easiest way to correctly position and solder the resisters, capacitators, and LEDs is by pre-tinning one pad, holding the component in place and very shortly reheating the pretinned pad with the component over it, with a soldering iron set to 350 degrees Centigrade. After the solder has cooled, very shortly tip the other end with tin and iron. Finished.
--- For ICs, pretin two pads at diagonal ends of the IC, hold it in position and shortly tip the two pretinned pads and let cool. The IC should now be properly fixed in position. Very shortly touch each leg with tin and iron. If all goes well you should be finished. But do a thorough check with the 10 diopry magnifying glass. If there are any bridges, just remove exces solder with the de-soldering floss and iron. But be carefull that you only heat one small portion of the floss and lift it when you seen fluid tin sucked in without letting it cool. If you move the iron too much, the floss my be soldered to some pads and if you then tug it, you may lose one or two (guess how I know ....:=( ))

3) The manual advised to start with the MPU and a second SMD IC. I think it's better to start with some SMD capacitators and get used to these very small components and the very short tipping with solder and iron. You'll be more relaxed when you come to the ICs. If you do have experience with SMD soldering, the adviced sequence is probably fine.

I still have to test the board and figure out which resistors have to go into the gyro amplifiers. But that's for later this week. And hopefully the motors and ESCs will arrive as wel, and mabye even time to make a very simple frame...
Jul 22, 2007, 08:36 PM
S.C.R.A.P.S Member
chargenut's Avatar
Good work Arthur P. I'm tempted, I have to admit, to get all the Mikrokopter parts and get soldering... but not sure my skills would be up to it.

I have a UAVP Set 4 on order and am not sure I can be bothered to wait for it...

Hmmm... I'll think on it a day and maybe start ordering all my parts for an MK tomorrow evening.

Jul 23, 2007, 04:46 AM
Registered User
Mark Harris's Avatar
Are the caps/resistors 0402 or 0603 footprint?
Jul 23, 2007, 05:24 AM
Hogster's Avatar
Watching with interest Subscribed

Jul 23, 2007, 05:41 AM
Registered User
Originally Posted by Mark Harris
Are the caps/resistors 0402 or 0603 footprint?
No clue what this means. They are between 4x2 to 3x1 mm large if that helps...... You want to do this in a reasonably clean environment. Drop one of those things on a messy table or floor and you're going to need a lot of luck to find it back
Jul 23, 2007, 01:00 PM
Zoom, zoom...
Trikster's Avatar
Cool! Cannot wait to see the finished product. These things intrigue me quite a bit.
Jul 23, 2007, 01:09 PM
Registered User
PeteSchug's Avatar
Originally Posted by Trikster
Cool! Cannot wait to see the finished product. These things intrigue me quite a bit.
I'm not even sure what is being built and I am intrigued.

Or maybe fascinated.

I will drop in from time to time until I know what it is and if I want one.

Jul 23, 2007, 03:08 PM
It flew...nearly!
Originally Posted by PeteSchug
I'm not even sure what is being built and I am intrigued.

Or maybe fascinated.

I will drop in from time to time until I know what it is and if I want one.

Me neither, but if ArthurP's building it I'm in!
Jul 23, 2007, 04:24 PM
Registered User
Hey, "no clue what is being buit"..... And here we've had this quadrocopter thread high in the forum for so long. For those who want to know what is being build, look here: I-m building from bare PCB with alle the soldering of all the eeny weeny bits and pieces. An alternative could be to buy an assembled flight controler here:, who had some listed on his site this morning, but they're sold out again. I think he hand-assembles them, so stock will probably not be very high. The mikrokopter shop will have partially assembled PCBs in early August, so you will only have to solder some larger parts (e.g. air pressure sensor). Another group developing such machines is but the shop who sells the UAVPs still hadn't delivered some 8 weeks after ordering, so I kind of gave up on them.
Jul 23, 2007, 04:41 PM
Registered User
Well I managed to test my MikroKopter (MK) flight controler this evening. Tests of voltages showed that the amplification of the gyros was off and needed to be reduced for 1, increased for two others by soldering in 220 ohm resistors. And, lucky me, the pad I lost was not needed in this case.

After that came the hard part. It should have been straightforward, but it just wasn't. It was more a matter of perseverence. Flashing the hex file with the boot loader and flight controler software occurs over a serial interaface through the MikroKopter Tool which included AvrDude. Flashing seemed to go well, but after flashing only the green LED came on and there was no serial communication with the MK tool. After several repeated attempts at flashing with results varying from no LEDs to green LED only, it was back to the Mikrokopter forum. However this also didn't provide much help other than being able to conclude that multiple people suffered similar fates. Some had problems with the serial cable, others with the fuse bits being scrambled. In the latter cases sometimes repeated flashing eventually resolved the problem. So checked the cable, resoldered some less than picture perfect spots on both the MK controler and the serial programming interface, and reflashed the bootloader + v. 0.58 flight software several times. On a final try, when I was ready to give up, suddenly loud beeping from the MK flight controler and a red and green LED lighting up !!! After turning off the flight controler, removing the programming jumper, connecting the 10 wire serial interface, and turning on the flight controler: MAGIC !!!

My MikroKopter flight controler is ALIVE !!!

Curves for roll and nick gyro in the MikroKopter Tool looked OK to me. Linear accelerator also seemed to respond well to horizontal movements and less responsive but probably OK to vertical movements. Even the air pressure sensor proved to be VERY sensitive after turning it on in the MK Tool and restarting tool and MK controler. However, the jaw gyro shows values from -5 to +5 max. And that doesn't look good.
So maybe a defective gyro there ???
Posted a questions about that in the MK forum and will investigate further over this week. But if that's the worst, it aint all that bad.

The main controler is alive and ticking, even if not yet in full health. So far the worst case might be needing to replace one gyro. That would still be a setback, but still a lot better than having trashed the whole main controler.

Hope to get the motors and ESCs this week. And I hope Quark's modification of the these ESCs is indeed as easy and effective as suggested in the forum. That would get me 25A ESCs at a lower price than the upgraded Holger ESCs and with a lot less soldering

I must say, that once you get the hang of it, this soldering really isn't that bad. It's just the hassle of getting those small parts from, with a minimum order of Euro 150.00 while you only need about Euro 30.00 of parts, which is a pain. I am contemplating a second MK as backup, but I-ll wait and see what the price is going to be of the partially assembled print or maybe go for the fully assembled one just to avoid the need to keep buying SD cards and other stuff.

An alternative could be to order a couple of blank flight controlers and all the parts, assemble them, and sell them on for a small additional fee, or sell them with parts with an add on to cover additional postage....... Wel if there are people interested in either the PCBs and all parts, or assembled MK controler and serial programmer at an assembly fee, just send me a PM. At sufficient intest I might consider either. No promises at this point though.
Jul 23, 2007, 05:04 PM
Registered User
Correction. They just posted the partially assembled mikrokopter controler. What they assemble are the main ICs, NOT the resistors. So this actually worsens the problem of having to order stuff from Reichelt: you need about 10 Euro's of "resistors" and another 140 Euros for an international order. But if there is an interest I-m perfectly willing to order multiple sets of "resistors" to so that others can get them off of me.
Jul 23, 2007, 05:05 PM
S.C.R.A.P.S Member
chargenut's Avatar
Nice work!!!

I'm impressed with the speed of your progress (and I don't mean that in a nasty way either). It must take quite some time to solder all those little components onto that board. You must have set a fair amount of time aside to do it.

Thanks for the build thread... very interesting so far... now I guess I just need to either... get a populated board, if one happens to appear in stock at any time, or get those parts ordered!!!


Jul 24, 2007, 02:35 PM
Registered User
Ordered a partially populated 2nd MK board today. They're just on offer, have the ICs already mounted. You still have to do those VERY SMALL caps and resistors and some bigger parts yourself. But once you have the hang of it, they really aren't that hard to solder. Just do not drop them anywhere other than on your parts for soldering tray. You'll never find them back.

Of course I ran into the Euro 150.-- limit at Reichelt again. So I decided to be a nice guy and partially fill it up with the additional parts for 3 partially assembled mikrokopters and for 3 serial programmers. So if any of you do want to build a mikrokopter, send me a PM and you may be able to get the small parts off of me for partially assembled MK and sercon at cost + postage + a very small rounding figure ;=)

Now I did NOT order parts for the ESCs as I-m first going to try to modify some commercial ESCs to understand I2C.

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