Student trainer mode

Post by **ShowMaster** » Thu May 05, 2016 6:24 pm

I'm on it! I'm thinking a non inverting buffer ic, but I have many fets and parts.
I'll know soon and then tidy up my design to post if it works. Time management is the issue.

Post by **ShowMaster** » Fri May 06, 2016 3:37 pm

For comments or DIY for those interested.
I'm sort of playing with this circuit and values. They are what I had in my Scrap parts box. A circuit sim seems to like it.

Post by **ShowMaster** » Sun May 08, 2016 12:31 am

Update again. I actually have this working ok and actually used these values. I was gong to use the 4.7k's and 1 ufd cap but had this assembled do I connected it up.
Works on the bench and later I'll try a smaller value input cap.
The unloaded output drops from 5v ptp to 3.8v ptp when plugged into the DX7.

Below is the actual circuit and waveform when the two tx's are connected and working as master and trainer.

Family issues keep pulling me away from the bench, but I'm able to make a little time and progress.

Post by **ShowMaster** » Sun May 08, 2016 2:36 pm

Then there's this 12c logic level converter idea?
I says it'll work down to 1.8 v on the low side with the fet used.
2ch ready boards on eBay for $1 if the fet is the same?
Time to brainstorm while I'm away.

: ImageUploadedByTapatalk1462718209.431400.jpg (52.42 KiB) Viewed 5109 times

https://learn.sparkfun.com/tutorials/bi ... okup-guide

Post by **ShowMaster** » Tue May 10, 2016 5:21 pm

JR S400 trainer ppm buffer 1.5-1.8v to 5v working and installed.
Due to time management issues, I decided to go ahead with the circuit I threw together that's working.
I've ordered several 2 ckt bss138 smd boards to try when the arrive in several weeks. The bss138 says it an buffer 1.8v to 5v. If so, it's a real fast and easy install.
For now I'm using my 2 fet circuit to move forward.
I've installed the board and quickly found a source for 5v, ground, and the low ppm signal the S400 sends to the trainer Jack.
As you'll see from my quick photos, the GREEN wire going to the trainer Jack is the ppm out. I just had to cut it and insert my circuit into it. The battery on switching is still controlled by the trainer Jack and no changes required there.
I've tried this so far with an older DX7, the reason for this nod, as well as a new 9Xtreme build and a Taranis B tx. All good so far. I'm sure it'll work with the plus and other brands as long as they can use the JR ch order or remap them.
I'm not sure if there's other tx's that won't work as a trainer due to a low ppm out level, but this should work also for them. The bss138 level changer buffer board may be the Swiss Army knife for this issue.
Also adding a trainer out function to tx's without one.
R&D needed there.
So below is a quick summation of a working setup I'll be flight testing soon. Feel free to improve on it.

Post by **ShowMaster** » Sun May 22, 2016 4:52 pm

JR S400 TX that I modified.

: ImageUploadedByTapatalk1463935925.615226.jpg (70.96 KiB) Viewed 5063 times

Daedalus66 · Post by **Daedalus66** » Sun May 22, 2016 8:49 pm

Thank you for that. I will resurrect my old S400 and give it a try.

Post by **ShowMaster** » Sun May 22, 2016 11:03 pm

I have several 12c level converters coming as in the schematic I posted, that may simplify the mod. All the parts are already mounted.
I may not be able to install one right away as I gave the JR back to the club instructors to try.
The fet quick attempt seems to work well so far.

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