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elossam

external servo mixer

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Does anyone have any scheme and hex file to make a external servo mixer (two imputs / one output) whith the following specs:

1) Absolutely no servo signal resolution reduction. Even those comercial ones claiming for more than 200 steeps resolution are a POS in softness and proportionality.

2) 1:1 mix but: A) each channel must individually be able to reach the 100% servo travel. B ) When mixed the sum of both signal will never go beyond the 100% servo travel range.

3) Possibility of choosing if both mixed signal are added or deduct from each other. (the same way a simple old V-tail Mixer works as they have two outputs and each one works in opposite way)

Have no possibility of doing it from the RC-TX as the mixed signal must come from an on board Gyro.

Thanks

Elossam

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Yes, PIC and AVR use different programmers. But if you search a bit you'll find some schematics to build yourself a fairly simple AVR programmer, like this for example: http://www.lancos.com/e2p/avrisp-siprog.gif

As the software is in assembly you wouldn't be able to port it to a PIC without entirely rewriting it. Better start from scratch, makes a good programming exercise :P

As a PIC I'd use my usual 12F675, providing the inputs aren't simultaneous (Futaba PCM). Fine with 1us resolution (1000 steps on standard throws).

Edited by Kilrah

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Thanks Kilrah.

I have no idea about programming but need to collect as much info as possible in order to call the right phon numer mate that will program it for me ;)

Your info has helped me alot, thanks

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Any luck with the hi res mixer search ?

I need a couple too.

Terry

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Hi Terry,

No, I have had no time to go ahead with that but hope to start with it at the end of the next week. It´s the only option I have for now to finish my own UFO proyect so I must do it ASAP.

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Thats why Im looking for a couple, Im building a quad.

Terry

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What mix scheme are your trying to use that needs only two mixers?

Mine is based on a 4 servo ccpm mix from a AP2000i electronic mixer running the roll and tilt gyros plus the pitch channel to each ESCs. Then for yaw I´m planning to add a third gyro to the rudder receiver output plus a servo signal buffer to support four outputs, to four servo mixers. Each mixer will manage the signals from the AP2000i and the ones from the rudder to put them out to the ESCs.

Edited by elossam

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Mine is based on a Helicommand. I plan to run the yaw gyro output into the 2 mixers to mix the yaw with the pitch and roll inputs to the Helicommand.

Seems like we are on similar paths.

Terry

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Have no idea about how the HC works but seems to me it´s not different than the AP2000i. Three inputs (elev/ail/pitch) and four CCPM outputs (each servo or ESCs in this case)

Being the airscrews turning two by two in different directions (fore/aft and left/right) and needing to vary the tork relation between both pairs/axis to get the yaw control, how does any change before the helicomand imputs provide the required rpm increase in both engines fom the same aixs while reducing the two of the other one in the same ammount.

May be you found the trick and I´m missing something but I´m not able to imagine the way to do it . Please let me know

Regards

Elossam

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Maybe Im thinking wrong but here goes .....

Both my roll props are RH and both my pitch props are LH so if I mix the yaw so that as the yaw signal increases it slows the RH props and speeds up the LH props it will turn and have no effect on pitch roll or alt.

By the way which speed controllers are you going to use ?

Terry

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After thinking about it I see you are right, it will take 4 mixers.

No problem, I am still at the stage of finding parts ;)

Terry

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Maybe Im thinking wrong but here goes .....

Both my roll props are RH and both my pitch props are LH so if I mix the yaw so that as the yaw signal increases it slows the RH props and speeds up the LH props it will turn and have no effect on pitch roll or alt.

By the way which speed controllers are you going to use ?

Terry

But yur using the RC TX in normal mode and the Helicomand as a mixer to get four outputs from three inputs, right? Having both engines from the ail axis turning in the same direction is the way to go but the CCPM mix will allways output "inverted" signals for each servo of the same axis (one + and the opposite -)

Think on this single channel. your externaly mixing rudder and ail to get a single output signal going into the HC for mixing. At the Helicomand input you will in anyway have a signal that once procesed will result in an aileron axis position where one engine will increase the rpm while the other is reduced but never both increasing or reducing at a time.

That´s why I found as the only way to do it, make the yaw mix just between the Ap2000i (HC) and the ESCs.

For ESCs I will rty this: http://www.hobbycity.com/hobbycity/store/u...?idProduct=4204

and this for power: http://www.hobbycity.com/hobbycity/store/u...?idProduct=5111

They are the cheapest ones I found and far away from quality winners but many guys have succesfully used them for the same project kind of machines.

I ordered at the same time a couple of mixers http://www.hobbycity.com/hobbycity/store/u...?idProduct=6321 but they are a POS and only the Futaba stile conectors will be saved from trash.

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Wow those prices are amazing, it will cost me much more in the UK.

Are you sure the 10A controllers will be ok ? I was thinking a bit bigger.

Terry

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I´ve not test them right now but as I said this is what many others are using without problems even loading the machines with photo cameras.

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Just me being over carefull I guess.

When do you hope to have it flying ?

Terry

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The airframe is ready with the engines fitted, the ESCs soldered and all the wirings ready. The Ap2000i is programed and the three gyros wayting to be placed. So only the f.....g Mixer chips are left. Once I get the four chips it requires no more than a couple of hours to make the little mix boards and solders to be ready for the maiden flight. So as soon as I find who can make it for me it will be ready.

Have you started your frame?

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No I have been working on another project for the last couple of weeks so nothing built for the quad yet. With luck I can get started soon, I will have all the parts by next week.

I will be very interested to hear how yours flys as its so close to what I am making. I was starting to think everyone else was using purpose built quad boards.

Terry

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I was starting to think everyone else was using purpose built quad boards.

Terry

Your not far away from true. I have heard only from a couple of guys that buildt them the way we want to do instead of going ahead with purpose boards, but those guys did it long time ago with old technic equipment and materials. Having at home the most expensive parts for the projec I think it´s worth to try it by mi own spending some Eur in those little engines and ESCs.

What we want to do using what we have is very close to what you can see in this forum http://www.rcgroups.com/forums/showthread.php?t=768115 They use a draganflyer board which has three gyros plus a IR sensor for outdoor stabilization. I can fit the IR sensor on my AP2000i as well, and so can yo do using your optic sensor and superior inertial configuration. So why can it not be succesfully done? even if it finally can´t, then I will start building a four engine depron airplane with the parts. ;)

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I was just looking at those mixers you linked to, do you think 1:1 mixing is going to be ok ?

I was thinking of a much lower value for the yaw.

Terry

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Sorry Terry, I didn´t realize you have a pending question here.

I would start using 1:1 mixing and reduce the rudder ATV value if needed.

In any way I found a group of people working on the walkera UFO board http://www.ckado.com/en/product_2069/UFO-0...pcb+35+mhz.html (Free shipping or add 3eur more for urgent shipping, I ordered mine this way last friday and was at home on tuesday)

It requires to change the supplied receiver (walkera PCM, or use an original Walkera TX if you can get one) to your one and to add some opto isolators to make it compatible with brushless engines. Other than that it comes with three gyros plus accelerometers, mixing board, two led outputs, two aux channels for camera operation (shutter and tilt) and a pot to set the right stabilization gain. sure it´s not a Mikrokopter PCB but for the price I decided to try it.

Read that link from the posted page to the end to have an idea about what is required

http://www.rcgroups.com/forums/showthread....878&page=12

I also got a new battery pack for my MaxiJoker2 and I need the AP2000i to be onboard asap so the UFO china board is the only option I´ve to play an UFO without spending too much money.

Will see.

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Dose that mean your AP2000i quad project is dead ?

Terry

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Dose that mean your AP2000i quad project is dead ?

Terry

Unless I´m unable to make the little walkera-UFO board work right I will no longer go with the AP2000i based one. Sorry but I can´t fight in all fronts at the same time and need the AP2000i working in my heli again.

May be it´s better this way so we both can afford the same goal of having our own UFO starting from two different points. The cost of the four mixers required is equal to the china board wich requires at the same time a PWM-PPM converter and a RC-RX adaptation to substitute the original Walkera. I will lose the IR stabilization capability but hope to be able to live with that if the gyro-accelerometer combo included in the PCB works as expected.

Later this evening I will post here the last v-mixer scheme I found that was the one I would use as it´s basec on a PIC and not on a Attiny, hope it helps you.

keep in touch

Elossam

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Thanks Elossam,

I have got some of those cheap mixers now, I will give them a go first but If they fail I have also programed my own 12F675 to give what ever mix I need by altering the value in the code before programing.

Terry

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