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Author Topic: Controlling a servo with 2 channels  (Read 3538 times)

MickK

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Controlling a servo with 2 channels
« on: November 24, 2015, 07:02:05 AM »

Hi all,


It's been a while since I've posted here, but has anyone controlled a standard servo using two different channels from the same receiver (Rx)?


At the moment I use Ch3 to move the servo left and right, and if I can also use Ch1 (which is used as the speed control) to move the same servo, only one way, only to the left, this would solve a problem that has been causing me no end of headaches.


Any comments would be appreciated.


Mick

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inertia

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Re: Controlling a servo with 2 channels
« Reply #1 on: November 24, 2015, 08:40:30 AM »

Forget it and work on a mechanical solution. A servo amplifier requires to "see" a single value for the signal pulse. If you try to feed it two different pulses at the same time it will confuse it!
One solution which springs to mind is to mount the first servo (Ch3) in a sliding tray and use the second servo to operate that sliding mechanism.
DM
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JimG

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Re: Controlling a servo with 2 channels
« Reply #2 on: November 24, 2015, 10:00:35 AM »

Does your transmitter have mixing capabilities? If so you might be able to mix channel one to 3 or vice versa.

Jim
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essex2visuvesi

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Re: Controlling a servo with 2 channels
« Reply #3 on: November 24, 2015, 11:37:18 AM »

Any Helicopter Setting on the TX should be able to do this as they mix the Throttle with blade pitch control


What exactly are you trying to do?
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MickK

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Re: Controlling a servo with 2 channels
« Reply #4 on: November 26, 2015, 05:52:12 AM »

Thank you gentlemen,


Jim and Mr essex2etc,
                                  I use a basic 4ch HK radio, i.e.  no mixers. I did consider that angle.


DM,
       I take your comments on board.  But I might try it anyway, even if just to prove the answer to myself!
       Your solution is ingenious, however there isn't enough room for sliding trays, let alone extra servos.




Thanks for your answers, and when I  get this little project up and running, I'll let you know.


Mick



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malcolmfrary

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Re: Controlling a servo with 2 channels
« Reply #5 on: December 02, 2015, 09:09:39 AM »

Its all been experience based theory and general principles and groping in the dark so far, but what is the actual boat and what is the actual problem?
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The Old Fart

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Re: Controlling a servo with 2 channels
« Reply #6 on: December 03, 2015, 04:03:31 PM »

Is there any one near you that can program 'PICAXE' chips.

small computer chips that will do what you want.

www.picaxe.com

ask on the site, some members are in Australia.

Subculture

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Re: Controlling a servo with 2 channels
« Reply #7 on: December 04, 2015, 01:12:02 PM »

I would agree with what Malcolm said, some more detail on what the mixing is required for, and also how the two channels should interact e.g. would one override the other.

MickK

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Re: Controlling a servo with 2 channels
« Reply #8 on: December 05, 2015, 08:23:07 AM »

Thank you folks,
Having delved into this issue, I came to the conclusion that the theory of using 2 channels on one servo (whether it works or not) , won't do ,what I want it to do.
Today I installed another (micro, high power,) servo into a very confined space,(just a 5 minute job!!!!!) which I believe should do the job. Took 6 hours!!!!

Subculture; There is no mixing available on the HK 4 channel radio that I use, it is a really basic 4ch radio, cheap, and suitable for the job in hand. I think it might be sold in the UK under the "Orange" brand.
Old Fart; I'm going down the Arduino road, I really don't want to change horses in mid-stream.
The whole project is a  radio controlled, robotic boat.
Thanks
Mick


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The Old Fart

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Re: Controlling a servo with 2 channels
« Reply #9 on: December 05, 2015, 09:12:56 AM »

presume the Arduino can read the two channels, pulsin on picaxe, then output single channel.pulsout.

happy programming.

Subculture

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Re: Controlling a servo with 2 channels
« Reply #10 on: December 05, 2015, 10:32:22 AM »

When i refer to mixing I wasn't referring to transmitter mixing. mixing can be done at transmitter and/or receiver end.

inertia

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Re: Controlling a servo with 2 channels
« Reply #11 on: December 05, 2015, 10:42:43 AM »

If you replace the two ESCs with servos this might do the job. It is very small (even smaller without the ABS box) but maybe still not small enough http://www.action-electronics.co.uk/pdfs/P82.pdf
DM
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g6swj

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Re: Controlling a servo with 2 channels
« Reply #12 on: December 05, 2015, 11:09:27 AM »

Arduino Uno (4 eBay / 18 genuine version) and a few lines of very simple code would achieve this, what's more you can programmatically decide/mix/perform calculations on/ apply logic to input levels (milliseconds) to achieve the output to the servo that you want.
Regards Jonathan




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inertia

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Re: Controlling a servo with 2 channels
« Reply #13 on: December 05, 2015, 11:59:08 AM »

Arduino Uno (4 eBay / 18 genuine version) and a few lines of very simple code would achieve this, what's more you can programmatically decide/mix/perform calculations on/ apply logic to input levels (milliseconds) to achieve the output to the servo that you want.
Regards Jonathan
Jonathan
Quite probably so, m'duck, but if it took Mick K six hours to squeeze an extra micro-servo into the model then this Uno beastie is not really a practical option, is it? "Horses for courses" as they say.
DM
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g6swj

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Re: Controlling a servo with 2 channels
« Reply #14 on: December 05, 2015, 04:31:43 PM »

Yup Inertia you may well be correct re Arduino Uno board not fitting, I posted on this thread because in one of his posts MickK said he was going down the Arduino route so I thought he would have taken into account the size of said item ie can he fit this in the boat!. I also wasn't sure if MickK struggling to fit the micro servo was simply due to the location it needed to be fitted to access control rods/surfaces etc having limited space and he may well have lots of hollow hull available elsewhere to stuff a micro processor board - So I guess the question is back to MickK - what space do you have to fit a gizmo into to tackle your 2 channels to one servo challenge as this may eliminate some of our suggestions?


The smallest commercially available Arduino board I think is 48 mm x 18 mm and weighs 13g and handles 7 channels of PWM.

It would be neat to understand exactly what you are trying to achieve as this in itself may open up other suggestions..

Jonathan
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g6swj

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Re: Controlling a servo with 2 channels
« Reply #15 on: December 05, 2015, 04:49:54 PM »

Maybe this would fit  - it's a "Femtoduino" 20.7mm x 15.2mm

Arduino compatible board which is very small (20.715.2 mm) and ultra light (2g) but has exactly the same computing power of the Arduino Duemilanove or UNO.
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MickK

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Re: Controlling a servo with 2 channels
« Reply #16 on: December 06, 2015, 06:27:44 AM »

Hi Folks,


Jonathon;  you are correct, there is plenty of space in the boat, I could fit a dozen servos in, use them as ballast maybe. The Uno as well as a motor control board, along with batteries, Rx, control arms, the list goes on, will all fit into the boat. The extra servo had to fit into a space that was not designed to hold 2 servos.


 Old Fart;   I have the programming in hand,[/size][/font][/size] [/size] If I was a rocket scientist with lots of experience in computer programming of any sort, there may be a way around my issue. The Uno only has to read pulse(n), I think PICAXE uses Basic, Uno uses C+ , maybe not compatible?Thank you.Mickp.s. Why has the font changed ? ? ?




It's all to do with the computer you are using.   

If you click on  'Preview'  after typing your letter, then you have 20 minutes or so do alter the scripting where you will find the formatting instructions.  (all them SIZE instructions)   %)

I sometimes do it to correct them but it can get a bit complicated with some machines

ken







 
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g6swj

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Re: Controlling a servo with 2 channels
« Reply #17 on: December 06, 2015, 09:11:07 AM »

Good to know you have space for Arduino Uno Beastie - I would suggest getting the genuine version approx 18 rather than the Chinese knockoff - I have however seen many posts on other forums where people have had great success with Uno's that cost 2.43 from eBay. Do you need any help with writing the code? If you do then I'll give it a shot and there are some Mayhem users whom I'm sure could help refine it. If you can describe the position of the 2 sticks and how they control the servo that should be a start howeve if your good to write your own code then let us know your progress and it would be great to see the code to let others know what the solution looked like.


Regards Jonathan
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MickK

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Re: Controlling a servo with 2 channels
« Reply #18 on: December 07, 2015, 06:59:46 AM »

Thanks Ken


I thought it was the "id_10_t" function in my brain!!!!!!


Thanks Jonathon, I'll plug away, hopefully by after Xmas the beast will be getting to a stage where I can progress to the next challenge. It's taken 12 months so far!
 That nasty 4 letter word (work) keeps getting in the way.


Mick

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