Look what came out of my reflow oven!


Hi guys,


Here I want to show you my new autopilot hardware which I worked on the past weeks.

The layout and the connections of the boards are chosen for my own convenience.

So airspeed sensor, receiver input, GPS, LEDs and I2C connections are at the front of the autopilot.

Servo output, serial ports, ADC and open drain outputs are at the back.


I also belief in the modularity, having two boards it is easy to replace the main board in the future when I need more performance and using the "expensive" IMU board again. It's still a small system with a height of 12mm and board dimensions of 62mm x 40mm, the weight is 35grams (mainly due to the stiff 1.6mm thick boards).


It's almost APM code compatible, only difference is the gyro+acc. sensor connected directly via SPI and the airspeed sensor which is connected to I2C via a one channel 16bit ADC.


It has all sensor "needed" on the IMU board, which are:

Compass:   HMC5883L

3 axis Gyro+Acc.: SD746 (or MPU6000 if it is coming available and prove to be better that the SD746)

Baro: BMP085

Airspeed: MPXV7002 (via ADS1100 16bit ADC)

Three open drain outputs

Three ADC inputs

Three Serial ports

I2C port (5volt)

GPS (Serial port, EM406 pinout)

Status LEDs


Main board:




TRACO regulator (max 36 volt input to 5volt output)

Eight channel receiver input at the front of the board

Ten channel servo output at the back of the board


Below are some picture of my work, now I have to test and do......some more testing :-)

Please let me know what you think of this solution......


Wish you all the best,




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  • @Alexander

    Great! That's exactly what I was looking for.

    Thanks also for the offer. In case, I will contact you but I'm still in the early phases of the project.

    Thanks again and let us know how the SD746 works.


  • @Mike,
    The problem with the max7456 based OSDs is the powerdisipation of this chip. But on rembizi OSD is also a linear voltage regulator which is heating up the board even more. What I did is making a small rembizi compatible board without the regulator and supply it with 5volts, works great, it's small and directly connected to my ap and getting it's power also from the ap. I will soon post a few picture of my complete setup.

    Thanks for your nice compliments, yes indeed the SD746 is looking very promising I hope it work out wel. If not I can remove it from the board and on the empty space on the board I can place the MPU6000 from invensense.
    If you want to order a SD746 then you can go to http://www.msc-toolguide.com/sd746.html
    It's €30,- per chip, I will have some small stock in the coming weeks so maybe I can sell them also if you want, let me know.
  • Alexander,

    great accomplishment ! That SD746 stuff looks promising.

    I had a look at web site of Sensor Dynamics but it looks like they only sell samples to "entrepreneurs".

    Is there any other way to get one of the SD746 for simple mortals ?


    Thank you


  • Moderator

    I also have Rembizi, but I am very concerned about heat; I have not discussed it yet. Too much heat, surely that is electrical inefficiency? I am talking outside of my experience. I continue to use Rembizi OSD, but worries me. I like the product other than that issue.

  • Nicely done! I see it looks very similar to APM with minor changes. How much time did it take you from the very beginning to ready board?

  • Farooq, there is not much to port, it is based on the apm+oilpan I did a the port for the sd746. I have to do the airspeed sensor and extra servo outputs and the three open drain outputs. But I start first with testing on the basic functions. Maybe there will be a branch of the apm code for this board in the future??

    I had ordered six boards, so five bare boards are laying around here. Including Osd and current/voltage sensor boards. The osd board I will show in the coming days, it's a really small "rembizi" osd which measures a 22mm x 25mm ....
  • Mike, I will not going to produce these board in high quantities maybe I will make a few boards if there is interest or sell some bare pcbs so people can assemble them self, but due to the fine pitch and qfn packages it is not an easy job to do. I can and will share the schematic and board files if interest out there, let me know. But all this after extensive testing is done. I did this for fun and hobby not for making money out of it, and so it will be open source or let's say hardware....
  • 1. Do you intend to sell these boards (if yes only PCBs or fully stuffed)

    2. What about the firmware porting?

  • Andre, due to my job it's easy to get all the necessary components, especially I'm in close contact and do direct business with Atmel. But you can buy all the components from Farnell, Digikey and for the gyro you can buy them from a German distributer MSC or directly from sensor dynamics in the quantity you want. There are no really special components on these boards...
  • Moderator

    I see a number of well thought out concepts here, perhaps lessons learned from working with ArduPilotMega/IMU?

    What do you plan to do as far as software? Are you thinking of producing these boards, or of publishing the layout for others to make?

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