Underwater ROV controller question

[CrazyCossack]

Ok guys, thanks for that! We'll keep searching for an IP network camera that'll do the trick.

In other ROV related news we finally got our patch ethernet cable working but it took a lot of troubleshooting, the cable is about 275ft, down from 333ft which was too unreliable. It seems not to work unless it's set to 10 MB/s, which hopefully will still work when we text it next with the 10/100 switch. We have a special coating on it and it performed without any loss in water.

We also have the ROV almost all assembled (minus electronics bay and motors everything is mounted). It's just barely on the side of positive buoyancy, when I push it to the frigid depths of my pool (12ft), it takes ~10 seconds to get to the surface, so we're very happy with that. The ROV is looking pretty worse for wear right now after all the tests haha, I think we'll soon have to give it another paintjob. Right now it's yellow, which is good for visibility, but really shows all the scrapes. Maybe black instead, although that decreases the odds of finding it in a lake haha.

[CrazyCossack]

Hey all, I hope you guys have no problems if I necro this post! I thought it might be better if I keep it all to one thread, but let me know if I should make a new one.

So we have been working on the ROV for a few months and the construction is now mostly complete. We disassembled the ROV and repainted it and have made a new electronics bay that should be big enough for all the electronics and our new camera. We have also got a new thruster. We've also done a new light aray I would take pictures but I think we'll wait on the electronics to reassemble it. For those of you who remember I have no clue about electronics and we'll really need help!

So the current list of electronics for a refresher is:
- 4X batteries  in parallel: together 11.v at 8800mAh
- 1X voltage regulator
- 2X sabertooth 2x5 motor controllers
- a 10/100 switch
- Arduino Duemilanove
- a Arduino eshield
- Two leak sensors kindly provided by madsci!
- Camera 12v 1.5A
- 3X thrusters 12v at 3amp each
- 1 thruster 12v at 5amp
- 4X LED cluster, 4.5 and 50ma for each cluster

Right now, we're very confused about what pins are currently used by the eshield and what are available to hook up the s1 of the motor controllers to. We'd like to power 2 motors for each motor controller, and have forward/reverse/stop etc. on each one. What mode should we use?

I'm working on an updated version of the circuit diagram since I showed the one we had to an engineer friend and it needed major revisions haha. I'll post it as soon as I'm able to draw it.

[CrazyCossack]

Here is the schematic. The ?? areas represent where we are confused about which pin to connect the motor controllers, LED, and the leak sensor to the arduino eshield.



http://img196.imageshack.us/img196/2917/65281943.png

[madsci1016]

Gee, that leak sensor circuit looks familiar.  

So you are asking how to hook the sabertooth controllers to the Arduino? The sabertooth's you have are serial controlled (right?), so you would have to create two software serial ports. You can create them on any pins, even analog ones; just as long as they aren't already used by your other hardware.

Looking at the eshield page:

"Arduino communicates with both the W5100 and SD card using the SPI bus (through the ICSP header). This is on digital pins 11, 12, and 13 on the Duemilanove and pins 50, 51, and 52 on the Mega. On both boards, pin 10 is used to select the W5100 and pin 4 for the SD card. These pins cannot be used for general i/o"

So any pins except 10-13 and 4 are open for any of the uses you mentioned.

[CrazyCossack]

Yes thanks so much for the leak sensor circuit!

That's what we were wondering, it seems from the product documentation there are 4 modes we could put the sabertooths in: Analog, R/C, Simplified serial and packetized serial. I would assume we want simplified serial?

Thanks for that, we couldn't figure out which ports were a being used by the eshield.

Any tips on how we could power the led array without overdrawing the current? And how do your leak sensors attach?

Cheers!

[madsci1016]

Simplified serial is easier, but the creation of software serial ports on the Arduino is taxing on it's processor and uses up memory.

You could use packitized serial and then connect both sabertooths just use one pin on the Arduino, it's hardware UART TX pin and not have the overhead of software serial.

You should look to see if anyone has made an Arduino library to talk to the sabertooth's using packetizied serial, that would be your best option. If not, I'll help you with the code.

Easy way to drive the LEDs is using a MOSFET that can handle the current.

I'll help you you out in better detail tomorrow if no one else does. It's off to bed for me now.

[madsci1016]

Sigh, 10 hour days at work are killer.

So, to drive the LEDS, you need a 'logic level' MOSFET.You will wire it like the middle circuit below.



The FETswitch line can be tied to an Arduino pin directly, or through a 100 ohm resistor just to be safe. Wire it so every LED has it's own current limiting resistor, and they all connect to the drain pin on the MOSFET. A MOSFET like this will let you switch 600mA currents.

I didn't see any easy Arduino libraries for the sabertooth, but we should be able to do it. So for now, the wiring plan should be to wire BOTH sabertooth RX pins to the Arduino's TX pin (pin 1).

The leak sensors can be connected to any available IO pin, except pin 0, 4, 10-13 since those are used by other things.

[CrazyCossack]

Cool thanks for the help! Packetized serial it is! I'm currently working on how to run the Arduino through the e-shield. So far I have been unable to really contact it at all, I think I have an older version, so the MAC address is not posted on the bottom of the device and it isn't. I've read I have to assign one which is no biggie. I have had a hard time figuring out what the IP address of the device is, if I plug it in directly to my laptop ipconfig doesn't show anything running on the LAN. I'll probably post something on the Arduino forums, but thus far I have been unable to even compile their sample ethernet sketches.

[madsci1016]

Yeah, can't help you there. Never used any such thing.

Though I bet you need to use a router to get an IP address assigned. Just plugging straight into your PC means you would have to set static IPs on both devices first.