ppm signal trought rs232

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TOURNEUR
Beiträge: 35
Registriert: Samstag 22. Mai 2010, 23:56

ppm signal trought rs232

Beitrag von TOURNEUR » Sonntag 23. Dezember 2012, 23:48

Hi guy !

For a fun application like control ROV trough rov ,and use thin tether ,I see no compatible hardware exist on profilab
to convert directly ppm signal .

In first think can use joystick ,in hardware section, but we can just acquire ppm signal com from usb radio or game pad .

So I 'm think it can exist possibility with rs232 serial port but how to do it in profilab ?

Does anybody can help me ?

abacom
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Re: ppm signal trought rs232

Beitrag von abacom » Freitag 28. Dezember 2012, 09:25

The question is too specialized for me. Maybe someone else can help or explain?
ABACOM support

TOURNEUR
Beiträge: 35
Registriert: Samstag 22. Mai 2010, 23:56

Re: ppm signal trought rs232

Beitrag von TOURNEUR » Samstag 29. Dezember 2012, 19:09

Ok ,Excuse me for the imprecision of my question .

I want to built one underwater R.O.V.
And want to control it by a netbook pc.

I want to use profilab for some pc control.

My first difficult come from tether ,from my pc to my unerwater rov .
I need use flexible and thin tether, like just one twisted pair and think about the PPM signal like radiocomand signal.

In ppm signal can travel 9 servo signal or more, but 9 is pretty good for my application .
And a ppm signal can work very far without boost interface .

But my first difficult is to have one ppm signal come from pc ,and don't see any profilab hardware compatible (like usb to ppm interface )
So I think RDS signal (Tx from RS232 signal ) can give me this ,but I'm searching how can do it in profilab software .

Actualy I 'm see this compatible hardware : http://www.electronic-software-shop.com ... top16.html
can coupling with this interface : http://www.buildyourowndrone.co.uk/8-Ch ... m-e8ch.htm

But I'm think rs232 can do it but I don't know how ...


Here I give you picture of my tether process
Dateianhänge
PC TO ROV.pdf
(84.14 KiB) 415-mal heruntergeladen

tom_g
Beiträge: 215
Registriert: Freitag 31. Oktober 2008, 14:59

Re: ppm signal trought rs232

Beitrag von tom_g » Samstag 29. Dezember 2012, 20:09

Good evening Tourneur,

ProfiLab is not a realtime application, even if you were able to create the logic for the RC PPM frame, you'll never achieve correct nor accurate timing (a PPM channel is timelength coded between 0.7..1.7 ms for the full actuator range of a RC servo).

(I had myself to refresh for what is PPM and found as a first hit http://www.mftech.de/ppm.htm) so surely no way directly from within PL.
But of course PL in conjunction with dedicated hardware (PLD or MCU), from which there is plenty around. Best suited would be a gateway solution (USB/serial to 8CH PPM) or such, most probably within the RC model community.

Hope this helps a bit in your further steps. If you have some hardware and need more help, contact the forum again.

ATB and good New Year from Thomas
Zuletzt geändert von tom_g am Samstag 29. Dezember 2012, 21:23, insgesamt 1-mal geändert.
Curiousity makes us progress !

tom_g
Beiträge: 215
Registriert: Freitag 31. Oktober 2008, 14:59

Re: ppm signal trought rs232

Beitrag von tom_g » Samstag 29. Dezember 2012, 21:18

Hi,

I had a brief look on your links. Yes, this is a possible approach to encode a max of 8CH PWM to PPM. Instead of an RC RX you obviously intend to use ProfiLab to produce the PWM. Although PL can easily produce PWM at 50Hz, the observations from my first answer still remain valid.

Hardware solution: Abacom's IO-interface seems to be able to produce PWM. (another ecomic, powerful, well suited and PL-supported IO board would be the PoKeys56E from PoLabs http://www.poscope.com/pokeys56e, which is extremly flexible, have a look. In PL the interface to PoKeys is ModBus TCP, and there are examples for PoKeys in PL already included)

As far as I remember, a typical RC servo needs 50Hz 0.5..1.5ms PWM. I am not aware about the PWM resolution needs of todays servos. But a min res of 6bits (64 steps) within the 0.5.1.5ms range are needed in my opinion for smooth movement. Thus the PWM generator must provide a min of 20 times more eq. 10bits which is most probably not a problem for a PWM generator at low frequencies.

How many channels do you need for the ROV application ?

ATB Thomas
Curiousity makes us progress !

TOURNEUR
Beiträge: 35
Registriert: Samstag 22. Mai 2010, 23:56

Re: ppm signal trought rs232

Beitrag von TOURNEUR » Sonntag 30. Dezember 2012, 10:45

Hi Thomas ,thanks for your help !

In Rov need 3 minimum pwm signal to control direction motor.
One for pump
Two for camera pan/tilt ,but one can be sufiscient .
And one channel for lighting .

7 pwm channel is a minimum for control .
I would like have more channel ,for other futures application .

Use this ethernet interface can be a very good solution .
And use a ethernet wire like tether can closing my problem .
But I need to work with a thin cable ...Ethernet wiring is not thin (4 twisted 24gauge + shield )
I must use a flexible and thin wire can work with different radius position .
If you know thin and flexible appropriate ethernet wire, I want to know it ...

But actualy ,I 'm trying to test this ethernet way with a double twisted cable pretty thin witch I take in my work.
But I don't know if it's can run, if yes Pokeys can be a very good solution .

tom_g
Beiträge: 215
Registriert: Freitag 31. Oktober 2008, 14:59

Re: ppm signal trought rs232

Beitrag von tom_g » Sonntag 30. Dezember 2012, 11:23

Hi,
the thin twisted pair flex cable will probably not be the only wire down into the water ?
please do specify, how you intend to send video signals from camera back to dry side, and how you power for the ROV (or has it batteries ?) May be send an updated sketch ?
I thought you'd rather multiplex the 8 servo signals (encoded as PPM) and send this signal over the thin 2wire line down into the ROV (wet side), where a 8CH PPM-decoder would convert the signals back to the servo compatile PWM. In that case, the PoKeys or another PWM-Interface is at your (dry) side, no need to feed Ethernet through the water :-)

ATB Thomas
Curiousity makes us progress !

TOURNEUR
Beiträge: 35
Registriert: Samstag 22. Mai 2010, 23:56

Re: ppm signal trought rs232

Beitrag von TOURNEUR » Sonntag 30. Dezember 2012, 12:07

I answer you my theory ...

If I use ppm signal to control my Rov trought underwater ,I need one bifilar wire just and another bifilar wire to travel video signal come from
my ROV ,using bnc to twisted baluns interface .

If I use ethernet protocol ,like the pokeys solution you send to me, it 's more complex ,but can be more good ,I listen pokey card system ,and
can offer lot of I/O possibility ,like control and status too !

Can control and see embeded status can be so fun on the same wire !
How can I travel video ? I thinking about one Ip camera conect on a same switch witch plug the pokey card
And 2 twisted wire tether can travel ,Control + status + colour video, but as I send you before it 's a theory ....

Think it's possible with ethernet protocol ,but of course in any system any inconvenient .
With PPM signal ,this is the limited number of channel and no possibility to have statut on the same wire but need no energy for control (less than 20 mA !
With ethernet system this is the power consumation 100x more than ppm system... and I see little (about 2A or more just for video an control system ! It's need to have lot of attention ...

Travelling power trought underwater is possible ,but for one I need to have Ac signal on Hight power ,to travel hight energy ,and can cause perturbation on control and video signal wire near this power cable, differential line can break this problem.

So I prefer use embeded cell on the Rov ,today with the lithium polymer we have lot of energy in compact pack ,it 's can be a solution ...
Or use Pb cell but can consum lot of place in the ROV !

I take any possibility ...

TOURNEUR
Beiträge: 35
Registriert: Samstag 22. Mai 2010, 23:56

Re: ppm signal trought rs232

Beitrag von TOURNEUR » Dienstag 1. Januar 2013, 19:41

HAPPY NEW YEAR 2013 ALL PEOPLE LISTEN IT !

At this time ,i tested my system with the 4 wire ethernet wire ,and it's work good !

About 60fts ethernet lenght witch connect my pc to : One switch witch distribute an IPCAM + 2 ethernet card (AVR NET) working on a profilab application.

But don't take total current consumation of the entire system, and I think can have big surprise ....

Thank's people's helping in my post !

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