twister cp 4 in 1, what's the 3rd trimpot for??

betty.k · Post by **betty.k** » Mon Jun 18, 2007 5:36 pm

i've been having some issues with my rudder trim lately, seems like the rudder trimpot does nothing.

so i popped open the case to clean it out with electrical contact cleaner and discovered a third trimpot on the esc/gyro unit (refer to pic below).

you can only access it by removing the casing, so it must be some sort of factory setting. the pcb tracing is really small and confusing so i'm unable to see what it's connected to.

anyone know?

Nasphere · Post by **Nasphere** » Mon Jun 18, 2007 6:20 pm

IDK about your heli, but on mine the rudder trim is just a centering pot.. You would use that to center the tail the best you can with the TX trim centered.

Is the gyro mixer on the board itself? Maybe that 3rd pot is the mixing level.

betty.k · Post by **betty.k** » Mon Jun 18, 2007 7:53 pm

the rudder trimpot on the esc actually does nothing.
the component is working (tested with multimeter), just has no effect on anything i can see.

Is the gyro mixer on the board itself?

i'd assume so, like most 4 in 1 units there is a separate 6ch rx (not pictured) and the pictured pcb has escs for tail and main motors and the gyro sensor (on the other side of the double sided pcb)

Maybe that 3rd pot is the mixing level.

what's that?

the weird thing is, on the workbench twiddling with the gyro gain actually seems to trim the rudder!

and twiddling the mystery pot affects the tail motor speed and does something to the gyro function that i'm not understanding with trial and error.

Nasphere · Post by **Nasphere** » Mon Jun 18, 2007 7:58 pm

When you're in the air and you give it throttle, the tail needs to speed up otherwise it'll spin. That's the mixing level.

betty.k · Post by **betty.k** » Mon Jun 18, 2007 8:11 pm

that could be it.

is mixing level usually a linear "more or less" adjustment?
eg, counter clockwise turns the level down, clockwise turns it up?

Nasphere · Post by **Nasphere** » Mon Jun 18, 2007 8:22 pm

betty.k wrote:that could be it.

is mixing level usually a linear "more or less" adjustment?
eg, counter clockwise turns the level down, clockwise turns it up?

Usually it is linear. But saying it's CP, it's gotta do inverted too.. I don't have a CP so can't help ya too much..

betty.k · Post by **betty.k** » Mon Jun 18, 2007 8:50 pm

no worries, i'm miles ahead of where i was before

betty.k · Post by **betty.k** » Tue Jun 19, 2007 6:25 pm

i've had an awesome breakthrough thanks to toyo at rippers!!!

TOYO wrote:blah blah blah, rudder trim enables the motors to turn in unison and apparently must be repowered after an adjustment before any effect is produced

i totally didn't realise this!! i'm used to trimpots that adjust things instantly like the steering trim on a miniz pcb.

but with the heli, the trimpot settings are only used during gyro initialisation in the first few seconds.

so if you make any adjustment on the 3 pots you need to power down the heli then restart it in order for the adjustment to take effect

after fiddling with the 3rd trim some more i think nasphere was on the money calling it a "mixing level" adjustment.
turning it way down makes it totally unresponsive to main throttle input without affecting rudder.
turning it up makes the tail motor run full speed with any throttle input.

so i'm working on finding a happy medium, if the tail can't keep up with throttle/collective commands it needs to be turned up.
if the tail motor does too much compensation it needs to go down.

fuck i'm glad i understand this now!!!!!

TOYO & nasphere