DIY Wireless Trainer/Simulator Solution (for kids)

The Background

I had been away from this amazing hobby for almost twenty years when a friend of mine sent me a link to an awesome video. The video led me to rcexplorer.se where I started reading, and reading and reading… A lot had apparently happened in the last 20 years and it didn’t take long before I ordered the stuff needed to build me my own rcexplorer tricopter 2.5. Rcexplorer also introduced me to Flitetest and I’ve been a follower since.  

I’ve been building and flying for a year now and my son has started to show an interest in my flying and been asking if he can start flying as well. So, in the spring I thought we would give it a go. Standing behind him while his flying, holding the sticks, is not really an option (at least not once he understand the basics), so I’ve been looking for a cheap, second radio to use as student radio in a trainer solution. The problem is that all radios are rather big and my son’s hands are small.

Then, during one of my daily “New Items”-browsing on HobbyKing, I found the Turnigy 5x Mini Transmitter. It was cheap, had five channels, dual rate and some basic mixing. And it was small! The downside was it didn’t have any trainer port. I really like the size though and it didn’t cost that much, so I ordered it.

The Build

I’ve done some Arduino projects in the past and was sure something could be done with it as a base to make a wireless trainer solution. I wanted to convert the five outputs from the 5X's included micro receiver into a PPM signal which I could then feed the trainer port of my 9XR with. And sure, after some searching I found this article over at openrcforums. It was exactly what I wanted, so I started planning.

The Parts

I ordered a 5V 16MHz Arduino Pro Mini. Any ATMega328 based Arduino would probably work, but the pro mini is small, cheap and I’ve worked with them before.

As I didn’t want an external battery to power the solution (for both looks and practicality), I wanted to power it from the Futaba trainer port on the 9XR, so I ordered a Futaba micro plug as well.  

Measuring the output voltage on the pins in the trainer port of the 9XR I found it gave around 14 volts, both on the battery pin and the switched voltage pin. Somewhat odd, since the battery was only around 10V. Anyhow, 14V is a bit much for the internal voltage regulator of the Arduino. I also had to power the receiver with around 5V, and since I didn’t know the current draw of the receiver I didn’t want to power it from the Arduino’s VCC pin which has a current limit. The solution were to buy  a separate voltage regulator. HobbyKing had a small UBEC with noise reduction which I ordered. However, HobbyKing lost my order somewhere in the warehouse so I ended up buying a step up down voltage regulator from a local dealer. I also bought a plastic box which could hold the electronics.

I figured I'd have some LEDs which could indicate power and communication. But the arduino code where not like my usual code so I used the code just as it was and added just one LED powered directly from the voltage regulator to have some indication of operation. Totally unneccesary though, but it adds some bling to the box :)

I had no major problems with the build, but once assembled I found out that the 9XR doesn’t take any input signal on the futaba trainer port (at least not mine), so I added a JR plug as well. It doesn't look as clean with two plugs but with a JR plug I could also use my wireless solution with my flight simulator. To be able to power it when used with the simulator I added a battery lead as well.

Below you’ll see what it looks like fitted in the box. I won’t cover in detail what I’ve done or why, I just want to show what you can do. This project requires basic soldering skills (which most into this hobby has) and also some knowledge about the Arduino IDE (to be able to compile and upload the code to the arguing), but it is information you can find on internet if you want to build one of your own. The box draws a little less than 70mA, without the unnecessary LED it draws not more than 50mA. There would have been no problem powering the receiver from the Vcc pin of the Arduino, so if you use a power source between 6 and 12V I would recommend to use the regulator on the Arduino instead of the separate voltage regulator (and save space and money)

The Result

I've flashed my 9XR with openTX and configuring the trainer setting was quite straight forward. I found this video useful.

The Cost

Turnigy 5X Mini transmitter: $22 (premium member price)

Arduini Pro Mini: $7

Futaba Plug: $1

Voltage Regulator: $6

Plastic box: $4

LED, resistor, wires, servo plugs and other stuff I already had: $5

Shipping: $10

Total: $55

$55 for a wireless trainer solution including the student radio is not bad and I’m very pleased with the result. There are commercial solutions out there which cost $100 and that don’t include the student radio. You are however limited to one protocol with this solution but that's not problem in my case. I’ve used the receiver which came with the 5X in my build, but you could of course use any receiver as long as the radio you want to use as the student radio can bind with it.

The Conclusion

I’ve tested it both as a wireless trainer solution and as a wireless simulator solution. And I have to say it works just as great as I had hoped. I’m also quite pleased with the looks of it. Time will tell if it works in the long run and if my son learns to fly, but he’s busy training for spring :)

The End

I'm very happy with the result. I found a small radio for my son and a solution to be able to buddy box with him and this to a low price :)

I've simply used the work of others (thank you) to solve a problem I had and I hope this article can help others. Leave any question in the comments below and I'll try to answer them.