X-1000 headtracker &PPM mixer => 8 chans to mx12

When flying fpv you quickly run out of channels with the low end transmitters. A 4 channel plane + pan and tilt already require 6 chans. Ifyou also want flaps or a switch for your osd of videoswitch, then you need at least 8 chans.
So I modified my good old graupner mx-12 to provide me pan and tilt on channels 7 and 8 (which it normally doesn't have)

You'll need the PPM mixer that you can find here : HobbyKing Online R/C Hobby Store : HobbyKing PPM Signal Mixer version B for Head-Movement-Tracker Gyro
This mixer takes the ppm signal from you transmitter and adds channel 7 and 8 before the ppm stream goes to the HF module to be sent out.

Disclaimer : doing this requires you to cut and solder wires in your transmitter. If these wires are soldered badly and come off, you'll loose signal and so loose control of you model. Don't do this if you have no understanding of electronics and have no profound experience in soldering

On top of the HF print 3 wire arrive from below, a red and 2 white ones. The red is +, the middle one is the ppm signaal the last one is - .



Cut them, but mark them first so you know which of the white is ppm. Mark both sides of the cut. I forgot to mark the lower side of the cut, and after cutting had to use the scope to find the ppm.



You can cut one of the supplied adaptors with the headtracker, or you can solder wires directly to the ppm mixer. I used the adaptors, but I think it's neater to solder directly (but more work)



To be able to switch the mixer-headtracker combination on and off, I added a switch. The switch either switches the ppm signal directly to the HF print, or it switches on the mixer and routes the ppm signal through the mixer and then to the hf print.



Here's a schematic of how to connect the switch. I also added a led to be able to see if the mixer-tracker is on :



The switch connects the middle contacts either to the upper ones, or to the lower ones. You may notice that the ppm signal is always presented to the ppm mixer, wether it's on or off. I don't think this matters because the input resistance of the ppm mixer was more then 10Mohm, so I think that should be fine. So far I haven't had problems with it. Ofcourse you have to do a good range check before flying.

It looks like this then :



Placement of switch and led on the inside :





ZAnd on the outside :



Replaced the connector from the headtracker with a servoconnector because that was easier to built into the mx-12.





In combination with a 8 channel receiver, like the corona RP8D1 for example, you now have all 8 channels in use, with channel 7 and 8 controlled by the headtracker.

Edited by u4eake - 13/Dec/2010 at 8:43pm