Ever notice that the CH3 buttons on the Spektrum DX3 radio are momentary? If using for shifting gears in your transmission, you have to hold it in place. Also, the switch (labeled "A" on the radio) is kinda clunky to reach.
Well, I thought I'd add another switch so it wouldn't have to be manually held in place. This switch will be in parallel to the existing CH3 switch, so if you still want the momentary effect, it will still work - just put the new switch in the center position.
This is the switch I used. It has to be a SPDT (single pole, double throw) "center-off" type. "Center-off" means that the center position is totally "off", and either up or down is "on".
The existing CH3 switch is actually two switches with one common leg. You have to solder the center pin of the new switch to the solder point marked as "2" in one of the pcitures below. Then, the other two connections of the new switch can be soldered to solder points 1 and 3. Then, hook a servo up and try it. If it's backwards, just swap the wires on solder pads 1 and 3.
To use this feature, CH3 must be set to the "3P" (3 position) mode.
The switch needs a 1/4" hole to mount. I installed it so it could be easily switched using my trigger hand thumb.