RC Groups

RC Groups
    DIY Electronics
        Help! Cheap TX hack

#1 _AL_ Feb 10, 2013 03:57 AM

Cheap TX hack
 
1 Attachment(s)
HI,
I recently bought a cheap & .... cheap micro RTF from HK. When it arrived I was impressed with the airframe but less than impressed with the electronics. After resoldering the pos wire from the battery box the TX started working & when I resoldered the rudder servo wire the rudder started working.... Good start except......

The TX is set in mode 3 or 4 (I use mode 1) & I can't even taxi it without my brain getting confused. I need to swap the left & right sticks.
The whole stick/ pot assembly is held in place by being soldered directly to the board. I thought about cutting pins, gluing the sticks to the board & running wires from the pots back to the circuit board but I'm starting to think I'd be better cutting the printed circuits up where they run into the chip & simply crossing the pot signals using wire.
Pic of the board below.

Is it possible (without being an electrical engineer) to simply break the path to the chip & cross over using thin wire? Could it be as simple as breaking the copper path with a dremel & soldering wire to one side below the break & the other side of the board above?
Any suggestions on how best to tackle this?

If it can't be done I'll simply install an AR6400 brick, the main excercise is to see if I can do it. If it works that will be a bonus.
Any advice appreciated.

Al

#2 _AL_ Feb 10, 2013 04:04 AM

1 Attachment(s)
Tried to make it a little clearer what I'm thinking...

#3 boaterguy Feb 10, 2013 08:26 AM

If you cut the traces on both pots, neither of them will be connected and swapping the wires won't do anything.
Find out what kind of microcontroller is in there and see if you can try to find the firmware for it, then it would be an easy reflash.

#4 microfan Feb 10, 2013 09:39 AM

I see no reason, why your plans shouldnt work. If you have no need to swap the not neutralizing side, you normally should be fine this way. If there have been factory adjustments made, you might have some off center issues.

#5 dmccormick001 Feb 10, 2013 04:59 PM

Have you tried getting the TX into a "programming" mode that might allow you to choose a different mode? A lot of TX have this ability, yours might have gotten itself into the mode it's in inadvertently. Most of the time it's accomplished by holding down some menu buttons, or perhaps some trim buttons, as you turn the unit on. I have a hard time believing that any company would build a radio nowdays that would not be compatible with the mode most R/C pilots in the US use.

#6 wilf370 Feb 10, 2013 05:15 PM

He is looking for mode 1 that is not popular in the us

#7 jakestew Feb 10, 2013 07:46 PM

Yep, it might just be better to learn to fly with normal controls, unless you're a lefty.

#8 boaterguy Feb 10, 2013 09:02 PM

I'm lefty, and I would never be able to use a mode 1.

#9 _AL_ Feb 11, 2013 12:54 AM

Thanks for the responses so far.

Boater Guy. Imagine pot 1 is the elevator & pot 2 is the throttle. I'm thinking cut the track on the board between pot 1 & the microcontroller, solder a wire below the cut for track one & solder above the cut for pot 2. reverse for the other side. Obviously there wil be 3 wires per pot so 3 cuts per control. Does that make sense? Essentially, move the sticks electronically without moving them physically.

DMcCormick, the TX looks like the cheap Parkzone RTF TX but it's a HK knockoff & the quality is very poor. Even if I knew how to activate programming mode, I doubt I'd find any instructions on how to identify how to, or what I'm changing. That would be the easiest way but I don't like my chances.

Jakestew. I've tried to taxi it & I'm like a cow with a gun. There is no way this brain is going to adapt to that mode. I'd give myself a 0.001% chance of making it past the 3 second mark if I actually got it off the ground.

Microfan. That's something I didn't think of. I'm thinking I'm going to try anyway & see what happens.

If anyone has any other suggestions I'd be happy to listen. I'll probably have a crack at it later in the week & I'll post pics of the carnage.

Al

#10 SadSack Feb 11, 2013 01:28 AM

1 Attachment(s)
Each pot has 3 pins, center pin is the output. So only 4 cuts needed. If you put a meter between outer pins they will be connected GND or V+ being used as a voltage divider.
I've marked on your picture in blue solder point you need black being cuts. Couldn't do other side pic just not clear enough.

But before cutting get you multi meter out and find out where center pin is connected too on chip and that will be your next solder point. Should only need cables fingers crossed.

Sorry if i got something wrong. Anyone watching say if i got it wrong :)

#11 jakestew Feb 11, 2013 04:31 AM

Quote:

I've tried to taxi it & I'm like a cow with a gun. There is no way this brain is going to adapt to that mode. I'd give myself a 0.001% chance of making it past the 3 second mark if I actually got it off the ground.
Mode 2 is the normal way your brain works. It's the way real planes fly, flight simulators, video games, PTZ cameras, and every other normal joystick operated device works.

Lefties might find mode 1 a little easier since fine motor control is better in your dominant hand, and mode 1 lets them control at least one of the important controls with that hand.

All I can suggest is playing some flight or rc sims, or just any other normal joystick type activity. Breaking yourself of bad habits like funky control schemes is worthwhile in the long run.

If you're determined to be set in your ways... the hack should be easy. One pin of the pot should be fed with a voltage, and another is the output the controller reads.
AFAIK there's no 100% standard way of hooking those up. The center pin is the "wiper" and is what moves with the pot. Each side pin is on opposite sides of the resistor material. So basically the center pin moves closer or further away from each of the side pins, which gives more or less resistance.

You'll want to figure out what pins are going where. I can't quite see in the pics where the traces are all going. It's not necessarily the center pins you need to swap.

#12 dmccormick001 Feb 11, 2013 09:05 AM

Quote:

Originally Posted by wilf370 (Post 24095191)
He is looking for mode 1 that is not popular in the us

Yeah, but most radios allow you to switch from 1 to 2. I figured he's in mode 2 now.

#13 SadSack Feb 11, 2013 02:12 PM

Quote:

Originally Posted by jakestew (Post 24099835)
Mode 2 is the normal way your brain works. It's the way real planes fly, flight simulators, video games, PTZ cameras, and every other normal joystick operated device works.

Lefties might find mode 1 a little easier since fine motor control is better in your dominant hand, and mode 1 lets them control at least one of the important controls with that hand.

All I can suggest is playing some flight or rc sims, or just any other normal joystick type activity. Breaking yourself of bad habits like funky control schemes is worthwhile in the long run.

Mode1 or mode 2 ain't a bad habit. you want fine control of the motor!??? There's a bad habit you need to break.

Quote:

Originally Posted by jakestew (Post 24099835)
AFAIK there's no 100% standard way of hooking those up. The center pin is the "wiper" and is what moves with the pot. Each side pin is on opposite sides of the resistor material. So basically the center pin moves closer or further away from each of the side pins, which gives more or less resistance.

You'll want to figure out what pins are going where. I can't quite see in the pics where the traces are all going. It's not necessarily the center pins you need to swap.

Thanks, I wasn't very clear in what I wrote.:eek:

#14 Bruce Abbott Feb 11, 2013 02:47 PM

Quote:

Originally Posted by dmccormick001 (Post 24101094)
Yeah, but most radios allow you to switch from 1 to 2.

But many don't. :mad:

I have changed over a few of these cheap toy transmitters. The hardest part is unsoldering and removing the gimbals (necessary to get the spring centering and ratchet changed over). To swap the elevator and throttle functions you only have to cut two tracks. Best to cut them right at the pot center terminals, then you have a good place to connect the wires to.

You can also swap the trim buttons if you want, but it's not strictly necessary (just remember where the controls used to be, and operate those trims!).

#15 JMP_blackfoot Feb 11, 2013 11:24 PM

Quote:

Originally Posted by jakestew (Post 24099835)
Mode 2 is the normal way your brain works...

...only in the parts of the world where is is predominant...:)


All times are GMT -5. The time now is 10:49 AM.