Author Topic: how to get full range for sabertooth from radio controller?  (Read 1355 times)

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Offline BANETopic starter

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how to get full range for sabertooth from radio controller?
« on: December 19, 2010, 02:43:51 PM »
Hey all,
I have a  Hitec laser 6 radio controller (not programmable :P)  and a sabertooth 2x25 that I'm trying to get full range from.  I have the sabertooth set to servo mode (750ms-2250ms i think) but the rc receiver is only putting out about 1000ms - 2000ms which makes my motor run at about 60% duty cycle max.  Ive already screwed around with the trims and pots but i've still not get a 100% duty cycle or close.   I know sabertooth can do 100% because i've hooked up a micro controller and no problem.  Anybody have any ideas? Do i need to open the controller and adjust some pots in there or something?

thanks in advance.

Bane
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Offline rbtying

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Re: how to get full range for sabertooth from radio controller?
« Reply #1 on: December 19, 2010, 02:53:26 PM »
If you've got a microcontroller, you could just use it to scale the RC signal to whatever you desire (or even better, use packet serial mode so you have more exact control).
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Offline BANETopic starter

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Re: how to get full range for sabertooth from radio controller?
« Reply #2 on: December 19, 2010, 03:12:58 PM »
I would prefer not to have my microcontroller on this robot :P since its just rc.  However, what you've mentioned is actually what i tried first but could never get my microcontroller to read the pwm signal properly.  The microcontroller language is BASIC which i suck at so that might have contributed to the problem.  But hopefully then i get my axon II (when ever that is :P) that will change.  Is there no adjustment on the rc controller itself?
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Offline Joker94

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Re: how to get full range for sabertooth from radio controller?
« Reply #3 on: December 19, 2010, 10:17:47 PM »
The out put signals form the receiver is designed for servos. on most RC radios digital or not the signal out put is generally set to control the center 90 degrees of a servo with a possible movement of 180, 45 either side of neutral(0 degrees). this feature allows for you to program trims, sub trims and travel distances without damaging the servo.

most analog radios can only handle trim, never the less they still only control the center 90 degrees.

Another of the radios features that may be responsible for this is the dual rate function. if you have a dual rates switch make sure that the switch is set to high as that will provide the full range.

a general rule is make sure all controls are in the neutral position when you first start to use the radio with the motor controller. from there you can adjust the trims and dual rates to get the desired performance.

You may have already covered the things i have mentioned but if you haven't it is worth a go. when i say most radios only control the middle 90 degrees when the radio is still on the factory settings i have not dealt with a radio that operated other wise, analog or digital.

Hope this helps

Joker94
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Offline BANETopic starter

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Re: how to get full range for sabertooth from radio controller?
« Reply #4 on: December 21, 2010, 04:51:20 PM »
thanks for everyones input

unfortunately the controller is already in duel rate mode :(.   For the laser 6 (heres the link) http://www.lynxmotion.com/p-72-hitec-6ch-rc-set.aspx I had to mod the right joy for tank mode.  I've noticed that when the right joy is straight forward (aka tank is driving forward) the duty cycle is about 60% for both left and right motors.  However, if the joy is pointed towards a corner (example: north east) then one motor will have 100% duty cycle and the other 0% (0% which is ok because you want to turn).  After thinking about it, this is an aircraft controller and it was modified for tank steering so I'm all out of easy adjustments for what i want to do. 

On another note, when i get my axon II (hopefully soon) it should be a breeze to scale the signals.  Does anyone have any code that take use the pwm from the rc receiver?
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