Thursday, February 10, 2011

Making the Turnigy 9X Transmitter RF Module Removable

The Turnigy TGY-9X is an inexpensive but very functional radio control transmitter available from in Hong Kong. It is designed for replaceable RF modules, but for some reason it was built with the included module 'hard wired' in place, by virtue of the antenna wire having been soldered to the module and run thru some holes drilled in the case to the antenna position on top of the unit.
There are reasons to remove the RF module (e.g., use a different brand, use the controls with a PC simulation program), but you can't. Unless you make a mod like this. Note that the antenna has moved from the top of the unit to the back of the snap-out RF module.

Here's how I did it.
1. Remove the RF module and open it (two phillips head screws, tilt the cover out and lift upward).
2. Unsolder the antenna coax from the circuit board. Note where the shield and center conductor are attached.
3. Open the transmitter unit (six phillips head screws in back).
4. Remove the screw that holds the antenna to the case. It's inside the case, just below where the antenna enters.
5. Remove the antenna and feed the coax out through the holes. You may need to remove the circuit board attached to the back (4 phillips screws).
6. Close the transmitter up - you're done with it.d
7. Remove the screw that holds the plastic bushing to the plastic stub of the antenna. Pull the bushing off.
8. Cut 9/16 inch(15 mm) off the end of the plastic stub of the antenna mount. This is so it will fit inside the RF case.
9. CAREFULLY thread the end of the plastic stub so you can fasten it with a hex nut. I used a 1/4-20 nut on which I notched the threads with a small round file to make a 'shade-tree' die. A regular die will work, but you have to be very gentle and work it back and forth slowly so as not to twist the plastic stub off. If you break the stub off, you will have to find another way to attach it!
10. Drill a 1/4 inch (6mm) hold through the back (outside) plate of the RF box. Choose a position so the nut will clear the inside of the box. There is already a hole covered by the label which you can use to run the antenna wire through, if you position the stub hole close to it. You may need to run a drill thru the hole to clean it out and punch thru the label. I also trimmed the plastic covering of the label to clear the bushing, so I could get a good glue surface.

11. Put the bushing back onto the antenna stub, feed the coax through the small hole, and bolt the stub up to the plate. Use superglue to secure the bushing, nut and stub.
12. Solder the coax back onto the RF circuit board. You could shorten the coax, but I didn't. Double check to make sure the shield and center conductor are not shorted together. Watch for little wire whiskers from the shield - they are tiny.
13. Reassemble the RF module into the box. I just curled the coax around in the open spaces. I also added a small lump of rubber foam to keep the circuit board from rattling.

14. Put the cover back on, and plug the RF module into the transmitter.
15. Be sure to range check the transmitter before you try to fly with it!

Friday, January 14, 2011

HK-500GT R/C Helicopter

This week, the parts for my newest helicopter kit came in from Hong Kong.
This is the HK-500GT kit.
Note that the body, rotor head and tail rotor units are factory-assembled. This makes the assembly of the kit go much quicker.

Here are the electronic parts needed to make the helicopter flyable. Clockwise from top-left:
ESC - electronic speed control (aka motor control)
Gyro - controls the tail rotor
BEC - voltage converter for receiver and servos
Servos - actuate the controls of the heli
Battery - actually, two of them in series are used
Not shown:

Here is the assembled model.

Other side - more photogenic, don't you think? (It looks like there are two rotors - the black one is the shadow from the flash on top of the camera.)

The kit went together very nicely. It took me 6 or 8 hours, as I was taking my time, measuring stuff, and being careful.
This version is a mixture of CNC (metal) and FRP (fiber reinforced polymer) components. HobbyKing has cheaper and more expensive versions.