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Topic: Kraftuino (newly "computerized" old RC transmitter) (Read 2830 times) previous topic - next topic


Mar 06, 2013, 10:12 pm Last Edit: Mar 06, 2013, 10:51 pm by DavidKyjovsky Reason: 1
My first project: to make an old RC trasmitter (79s Kraft) useful again, by changing the hf frequency to 2.4 GHz (Jeti Duplex HF module) and designing a new, computerized coder.
Why do that, when you can buy a fairly smart chinese Tx for USD 50 or so? I simply needed an excuse to do some more extensive project (in order to force myself learn the Arduino code), and not least, I always loved the look and feel of those fine Kraft radios.
The project is almost finished now and most of the features are implemented correctly. I have added a cheap (Nokia 5110) display (84 x 48) graphic display and 5 control buttons. The display is housed in a panel (that was printed on a Prusa 3D printer) on top/front of the Tx box. It is arguably spoiling the classic looks of the Tx, but I wanted to put it together and start coding in reasonable time. Maybe one day I will re-do the panel.

The functions implemented (and working) so far:

service menu:
-stick calibration (center and range)
-erase all models
-list EEPROM on the screen

system menu:
-model select (out of 8 model memory)
-erase model data

model menu:
-adjustable dual rates and expos (switch selected)
-servo reverse
-servo throws and subtrims
-batt voltage measuring and alarm
-4 free mixers (any of 8 available channels to any other), permanent or switch activated, with offset
-aileron differential
-prefabricated mixes (delta, v-tail, flaperon - flaperon with extra mixes ele-flap and flap-ele)

list of things still to do:
-trim reset, i.e. make the trim electronically and move the analog trim tabs to the neutral (very useful when you change planes ;))
-model name (8 chars)
-throttle curve (maybe)

at this stage, I have realized that it is doable - and the Arduino Duemilanove I have used is fast enough for this (the main program loop still goes through more than twice inside the 22 ms pulse frame).
All in all, this taught me a lot, and I would surely do certain things differently now (like make the program more structured, with more focus on reuseable functions). The program memory used up in this stage is cca 18 kB, still more than enough left.


Nice job!  It's always good to see a classic transmitter put back into service.  You might look at Gordon Anderson's MicroStar2000 Encoder for more features you could add to your design. 



Very cool project. Some of those vintage R/C transmitters had very high quality mechanicals, joy sticks, etc. so nice concept to refresh the electronics.

Care to share the code some time?



@Lefty: I will surely post the code, but first I have to finish it and second, I have to add some comments in English (so far commented mostly in my native Czech), otherwise I suspect that it would be too much of a mess to be of help to anybody. And yes, the 79 Kraft had some of the most advanced (at that time) and still very good stick mechanics.

@Jon: thanks for the link, amazing project. I have no shortage of ideas for more features, but I suspect that after the project reaches some level of perfection, I will shelve it. One thing that would be interesting though, to port it to some hardware with digital trims. I have even bought this cheap transmitter with the idea to gut it and install Arduino Nano with the Jeti HF module: http://www.hobbyking.com/hobbyking/store/__16238__HobbyKing_HK6S_2_4Ghz_FHSS_6Ch_Tx_Rx_Mode_1_.html

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