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Author Topic: Adding throttle trim to a Spektrum DX2E handle conversion  (Read 2798 times)

Offline bill bischoff

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Adding throttle trim to a Spektrum DX2E handle conversion
« on: May 10, 2013, 08:10:47 PM »
I am using the Spektrum DX2E radio as the basis for my 2.4 ghz transmitter handle, as are other people. One problem with this particular radio is the lack of useable throttle trim. Being designed for car use, the throttle trim works to adjust the idle position in the middle of the trigger's range. It has no effect at the ends of the throttle travel, where we would need it most. I think I have come up with a relatively simple solution. I have not actually done this yet, but I can see no reason why it would not work.

Since most people won't be using the steering channel for anything except maybe a slider release, and the steering has a functional trim and also an overall travel adjustment, simply use the steering channel for throttle. Both the steering and throttle potentiometers have 3 wires soldered to the main circuit board, so simply connect the throttle trigger pot where the steering pot goes, and vice versa. Now the trim and travel adjustments work with the throttle instead of the steering. Of course the throttle servo will need to be plugged into the steering channel on the receiver in order to work.

I plan to build another transmitter handle soon and incorporate this modification. If anybody beats me to it, tell us how it works (or why it won't!).
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Offline Mike Anderson

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Re: Adding throttle trim to a Spektrum DX2E handle conversion
« Reply #1 on: May 10, 2013, 08:26:39 PM »
On the Hobbyking Tx that I converted the throttle channel had trim which worked as normal, but the steering channel had "dual rates" as well as a trim.  It is really more of an overall range adjust pot and will be handy for using with multiple models, since this one doesn't have memory. Plus, the pots plug into the circuit board so swapping the plugs was all that was necessary to do this mod.
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Mike@   AMA 10086
Central Iowa

Offline Melvin Schuette

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Re: Adding throttle trim to a Spektrum DX2E handle conversion
« Reply #2 on: June 27, 2013, 08:24:37 PM »
Bill, Mike and everyone else;

Just finished up making my C/L-2.4 ghz handle tonight (OK not quite, I still have to mount the TX battery to the unit).  Like Mike I used one of the Hobby King radios and swapped the throttle and steering plugs.  Then I replaced the pot from the steering wheel with a 3 position micro switch and two resistors.  The pot in the radio measured 5.5 k ohms and I could only get 2.3 k ohm resistors from my Local Radio Shack.  The three position gives my 90 degrees servo travel.  I haven't tried other resistors to see if it will effect the servo travel or not. 

While looking on Ebay I saw that Specktrum sells a three channel car radio.  The 3rd or Aux channel can be set up as liner, 2 position, or three position.  It also has travel adjustments for all three channels. Next conversion project.

Melvin
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Joe Just

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Re: Adding throttle trim to a Spektrum DX2E handle conversion
« Reply #3 on: June 28, 2013, 02:31:59 PM »
All this sounds way beyond my ability.  I too have a "car" type radio and here's how I control the throttle.  Fast speed, just pull the throttle trigger back with my left hand middle finger. After high speed I just take my finger off the throttle and the plane reduces speed to about half throttle.  This allows me to then use my left hand to jerk the down line as I give full up and the release  the hook an d the hook comes down. Then, I use my middle finger again to slowly "push" the trigger forward. If I go too slow all I have to do is release my middle finger, or ease off the pushing and the plane speeds up.  Right now I am currently flying the slowest laps I have ever flown!
With all that said I once again claim no skill in flying, building or any other expertise in this hobby.  If you have the skill to re-work a radio I admire your skill and desire. If I tried any of the changes you guys are mentioning I would just ruin  an otherwise economical radio.

(Now if you think I really am sane consider the idea brewing in my mind of building a "British" Carrier deck (slightly reduced in size) to fool around with.  My flying site is getting so I am having trouble getting off the ground due to very high weeds, etc. Mowing it is out of the question and using a long piece of indoor/outdoor carpet is a pain. Maybe I should start a new thread to keep this 2.4 stuff as is)
Joe
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Offline john vlna

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Re: Adding throttle trim to a Spektrum DX2E handle conversion
« Reply #4 on: June 28, 2013, 07:46:30 PM »
Joe, et al,

I have been using the HK 2 channel car radio. The only mod I have made is to change the trigger spring position so low speed is all the way forward. The wheel is used to drive a servo slider release. No mod is required because the movement from mid range is enough to release the slider.

The trigger position is easily changed by adding a small wood block to provide a new pivot point. Since I fly primarily electrics no throttle trim is required. The TX is matched to the ESC and must be at minimum, nominally 1ms pulse, or the motor won't start.

John

PS Here is a thread which shows, among other things, how to change the HK trigger. http://www.rcgroups.com/forums/showthread.php?t=1751817
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