Modding a Futaba FC18-Remote

Today i finished the modification of my remote 🙂

Its an old Futaba FC18v3. I still had that one left from my first experiences with model aircrafts 15 years ago. I hate throwing stuff away, so I bought some new bits to make it usable again.

Now it features:

  • Powered with a 3C-Lipo (not shown in the pictures)
  • Blue Backlight LC-Display
  • FrSky DHT Transmitter module
  • Bluetooth interface for FrSky telemetry

The complete setup draws about 150mA @9V (with all modules powered on). That will make it run more than 10hours with a 1800mAh LiPo.

The Bluetooth and LCD module were both ordered from Ebay, the FrSky stuff from Hobbyking.

The installation of the different parts was pretty straightforward.  I removed the old 40Mhz-PPM-Transmitter and soldered the 3 wires for the new 2.4Ghz module. The old antenna was removed, also i moved the CAMPAC module in order to use that space for the additional LED-and-pushbutton-PCB of the trasmitter module. The Bluetooth module only has 4 pins, GND,+5V,Rx,Tx which i all hooked up to the FrSky. Since the FrSky-Pins are RS232, i modded the module to output TTL-Signals by accessing the UART directly. Unfortunately i didn document that, but you can find several images on google how to do that.

Changing the LCD-Module also was quite easy. Its a standart HD44780 module with a 14Pin connector. Some of the pins are not used because the FC18 runs the display in 4bit-mode. Basically i just removed the old module and soldered the wires 1:1 to the new one. Then i added two wires for the backlight which also runs of 5V.

The last part was setting up data display on my smartphone. Fortunately some other people already took care of that. I just installed FrSky Dashboard. Done 🙂

A new USB2DMX based on PIC18F24K50 chip

I was in need of a cheap USB->DMX interface and decided to build my own. Searching the web I fould quite a lot DIY solutions. But most of them were unsuitable for me.

My design features:

  • low cost (about 10€)
  • open source: schematic and board are licensed CC-BY-NC-SA, the firmware is GPL (except microchip files)
  • a real rs485 transceiver
  • signal-generation by the Microcontroller (no bit-banging like the ftdi-dmx interfaces)
  • bootloader to update the firmware (thats what the switch is for – rescue mode)
  • fits into a ‘G027’ case (kemo-electronic)

If you take a look at the schematic you will see that the processor used is a 18F2550. But its possible and recommended to use the 18F24K50 which is cheaper and doesnt require a crystal oszillator. This is due to the fact that i made the initial design with the older controller (which i had at hand during the time).

On the software side there is a patch for ola. You will notice that reworked the ‘opendmx’ driver (i failed adding a new driver/directory to the build system).

There is no need to patch ola anymore. The karate-plugin is now in the mainline-tree.

 

Please respect the CC-BY-NC-SA licence when downloading and using it 🙂

20130506_kldmx_usb2dmx_Firmware

20130506_kldmx_usb2dmx_board

Reworking a FrSky D4R-II Receiver

Since i want to use telemetry with my soon-to-be-finished uavp-ng quadcopter i decided to use a FrSky two-way-telemetry system. Unfortunately the enigneers at FrSky choose to invert the serial signal which wont work on the hw0.24-mini.

Thats why i took a closer look at the receiver pcb. Fortunately it was quite easy to identify the UART-Pins with TTL levels. I removed the two transistors and some resistors which arent needed anymore.

The pinheader was also removed in this process. I added a bridge on ch3&4 to active CPPM-mode.

As a additional modification  a voltage divider was installed. The AD2-Input of the receiver works up to 3.3Volt. With a 3k3 and a 10k resitor i was able to build a network with a convenient 1:4 scale factor. With 4*3.3Volt > 13V i can monitor the voltage of a 3S LiPo 🙂

Building a quadcopter – Electronics

This is how my Workspace looks after a few hours of debugging 🙂

I did some work on quadcopter-frames in the past, so inspired by the NG-UAVP-Project i decided to build my own quadcopter.

Since those guys offer blank PCBs i ordered some and build a Flight-Controller (hw0.24-mini-r2) and a Quad-Brushless-Controller (ngblc-r2). After some trouble with customs/taxes and missing parts i was finally able to assemble and test both boards. As always not everything works out of the box (soldering errors, missing parts, …).

  • Make sure to populate R68/R69. Those are current-limiting resistors for the backup battery for the Venus-GPS and the RTC. I left them open in the first place sind i didnt populate the battery. However, the Venus-GPS needs power at the Vbat-Pin to work. I spend about 3 hours searching for errors in the serial-communication :/
  • Check the supply voltages of each chip. The coil in the the LC-Filter for the MPU-Accellerometer was broken; however the MPU somehow still worked (eg got some supply current over clamping diodes), but did not answer SPI-requests correctly.
  • Cabeling is also an issue. The picoblade connectors are nice and small, but sometimes dont give good contact. I had some issues with the external-i2c-sensor bus because one pin didnt provide good contact.

There are still some open issues:

  • The LIS3L-Accelerometer wont get recognized on the SPI-Bus
  • On the ngblc there seems to be at least on misplaced part. On of the supply-voltages drops down because of overcurrent. I am still investigating this.

 

As next steps i will finish the mechanical setup. Mount the motors to the frame and do some wiring.

Lasercut Puzzle

Puzzle made out of 5mm HDFI made this for my niece (currently 16months).

Its made of 5mm HDF wood.  I did a google-image-search to find suitable pictures and traced them in Vcarve.

The text and the DIN-Label-Box in the lower right were exported from eagle. I was to lazy to draw them myself.

In the first version i just cut along the vectors which resulted in a really tight fit. The gear was almost impossible to remove and put in again. For the second version i duplicated the lines with an offset of 0.3mm which did result in a larger gap. Now all the parts fall out by themselfes if you turn the puzzle around.

The two sheets were glued together with basic wood-glue. The lower sheet also features ‘eject-holes’ (you can see them under the ruler and nut). That way you can push out the pieces from behind.