Corona 2.4 DIY

If you've been building electronic bits or modifying stuff you've bought then tell us all about it here. A good place to discuss the installation of 2.4GHz DIY modules too.

Re: Corona 2.4 DIY

Postby jazzboy » Sat Dec 18, 2010 4:20 am

Details on the Kraft retrofit would be fantastic.

Cheers,
Andy
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Re: Corona 2.4 DIY

Postby jeffie8696 » Sat Dec 18, 2010 4:29 am

Here it is from the man himself. I copied it from a post he made.
You will need to open up the back of the transmitter. Pull out the module. You will see two rows of female pins in the transmitter that the module plugged into. Ignore the top small row. On the bottom row as you are looking at the back of the transmitter the right pin will be the + power. The center pin will be the modulation PPM line. The left pin will be the ground. I got a pin connector that would plug into the female connector in the Kraft transmitter to wire everything to.

On the FRsky (or Corona) hack module there will be 3 wires. + power, ground, and the PPM modulation input. DO NOT CONNECT THE PPM MODULATION INPUT TO THE CENTER PIN ABOVE FOR THE MODULATION OUTPUT OF THE TRANSMITTER!!!!

The PPM modulation output of a Kraft is inverted with respect to all the other popular transmitters on the market. Also the voltage swing on the Kraft is larger than the FRsky (or Corona) module wants to see. So the modification I needed to make is to invert the modulation PPM pulses and lower the voltage. I did this with a simple NPN transistor inverter and I used a 5 volt regulator on the collector. (If you need I can detail this.) So I built a little PCB with one transistor, a regulator, and a few resistors. This PCB must be connect to the power pins (per above) in the transmitter and the PPM modulation pin. The output of this PCB goes to the FRsky PPM modulation input line. The FRsky also gets it's power from the pins in the transmitter. (I have thought about a different way to do this would be to use a single op-amp as a inverter with negative gain. Any thoughts out there on this?)

The little PCB that inverts the signal I built up as small as I could. Seeing I was using parts that I had on hand, I used a larger regulator than I needed but it works. I enclosed the PCB with some heat shrink tubing with 4 wires coming out of it, +,-, PPM modulation input and PPM modulation (inverted) output. I put this little PCB under the PCB that the original Kraft module plugs into with double stick tape. I put the FRsky module with double sticky tape where the original Kraft module would be located. Once everything is wired and mounted there is one last step, mounting the bind pushbutton and LED PCB. FRsky unlike Corona does not give you a drilling template. I very carefully measured the centers between the LED and bind button to be .312 inch. I located this on the top of the transmitter between the antenna and the slider for channel 5. I drilled the two holes with a .130 inch drill on the top. Next I used two 2-56 screws and nuts to mount this assembly inside the transmitter.

Antenna....remove the Kraft assembly. The hole in the transmitter is too large for the FRsky antenna mount. Inside the transmitter I used a quarter inch washer and on the outside I used another quarter inch washer. The washer I used on the outside is thin copper and matches the gold look of the transmitter very nice. I got them at Lowes for pocket change. I put the original antenna ground lug into this assembly then fed through it the FRsky RF connector to be used as the antenna mount.

The original Kraft antenna wire (white) with a solder lug is still in the transmitter. I put a piece of heat shrink over the solder lug to insulate it and tucked it under the module mount PCB.

One of my goals in planning this out was to be able to put the transmitter back to 53.2 mHz if I wanted. The only thing I can not undo was drilling the holes for the bind button and LED. I don't think I will ever restore the transmitter back now. I am going to leave it on 2.4 gHz. I do have one more of these Kraft Spectrum 6 transmitters to think about doing a modification to.

I hope this helps. Let me know if you need more information. This can be done in a weekend once you have all the parts for a low cost. I hope I didn't get too detailed but I don't know your background so more info is better than not enough. I've also done a Kraft series 74 for a good friend and it involved similar work.

There is a thread in RCG that is over 100 pages long on the FRsky hack DIY module. Lots of good info there.
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Re: Corona 2.4 DIY

Postby JMP_blackfoot » Sat Dec 18, 2010 2:49 pm

Unless I am mistaken, the output of the Kraft encoder is essentially an open collector PNP transistor from battery positive.
I would have thought that a simple 2.2k or 1.8k resistor to ground and a Schottky diode in series with the PPM signal (cathode encoder side) would do the job.
In case of the latest FrSky modules with diode included, just the resistor would work.
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Re: Corona 2.4 DIY

Postby jeffie8696 » Sat Dec 18, 2010 8:22 pm

:shock: I will have to ask. :? (something about a shot of something and a catheter? )
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Re: Corona 2.4 DIY

Postby jeffie8696 » Sun Dec 19, 2010 8:15 am

"I didnt know what the PPM modulation output schematic looked like so I did what I thought would be safe....and it works."

And I trust em, he is a super smart kinda guy. :D
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Re: Corona 2.4 DIY

Postby JMP_blackfoot » Mon Dec 20, 2010 2:37 am

"....and it works."
Can't beat that !! ;) 8-)
Many schematics, including some of the Kraft (or Heathkit, same) Tx and Rx here:
http://www.e-radiocontrol.com.ar/?Historia_del_R%2FC
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Re: Corona 2.4 DIY

Postby jeffie8696 » Mon Dec 20, 2010 5:32 am

Thanks for the link I forwarded it to him.
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Re: Corona 2.4 DIY

Postby sdost » Tue Aug 02, 2011 8:23 pm

I am looking for feedback on Corona reliability.
I currenlly have a Futaba FC16 transmitter with the Corona DTY set implemented and also a Futaba FC28 with the Corona CT8F tranmsmitter module. Receivers used are CR8D. With both systems I have experienced unexplainable lockups (fail safe) while flying. All resulting in glider crashes. It seems that when Corona receivers goes ino the fail-safe mode no recovery is possible anylonger and a crash will be the outcome. In both cases lockup happened when flying with quite a number of other pilots. Flying with a very limited number of pilots never gave a problem. Contacting Corona RC, even in chineese, is a waste of time since you will never get an answer. Any words of wisdom or should I just go to Futaba FASST?
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Re: Corona 2.4 DIY

Postby jeffie8696 » Wed Aug 03, 2011 4:27 am

I have not had any issues but my flying is limited to only a few other flyers. I am sure the Futaba FASST system is superior if you can afford it.
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