Documentation for 2.5 Controller Board posted to Github


#1

All the documentation for the new OpenROV 2.5 Controller Board has now been posted to the OpenROV-Electronics GitHub site-

https://github.com/OpenROV/openrov-electronics

Included are a pdf file of the schematic and a layout diagram, the Eagle design files (.sch and .brd), the bill-of-materials (BOM), and the Gerber files of the completed layout.

I've started work on an application note for the board, which will help guide folks who want to tinker with the new board, either in an OpenROV or in an ROV design of their own. For now, you'll have to just rely on the schematic and the layout drawing. If you have comments about the design, please let us know! We're always looking to improve the design of OpenROV.

The first production batch of the boards came in a couple of days ago, and we're shipping out pre-ordered OROV 2.5 kits now. Once we've filled the backlog of kit orders, we'll start selling the controller board as an individual item on the web store.

-Walt


#2

Hi Walt,

Looking at the specs of the new v 2.5 controller boards, i notice there's 6 x PWM outputs on J8.

Would i be correct in assuming the 3 of these are required for the ESCs?

Kind regards,

Phil


#3

Hi Phil:

That's correct. A stock version 2.5 ROV will need 3 servo outputs for the ESCs, and 1 for the camera tilt servo, leaving two spares.

-Walt


#4

Hi Walt,

That's great news.

In terms of upgrading, from a mechanical perspective i suspect it would be possible to add a fourth thruster for lateral/straffing movement or even a simple one servo manipulator.. Or both.

Phil


#5

Hi Phil:

We're hoping that by providing a lot of extra capability in the electronics, it will spur a lot of creativity in the OpenROV community for new designs- manipulator arms are talked about a lot, and I think a structural redesign that has a small lateral thruster would be pretty cool as well. Here we're toying with the idea of adding external LED lights to cut down on the backscatter in silty environments.

The change to a DB-25 connector from the earlier 18-pin Molex opens up a lot of possibilities for hanging external stuff on the outside of the ROV, as long as you pot the wires into the endcap beforehand. Even after you run a complete I2C bus to the outside world (Power, Ground, SDA, and SCL), there are still six spare pins left on the DB-25. So adding the wiring for a small lateral thruster or external LED lights is no problem at all.

-W


#6

Hi Walt,

Looking at the revised list of specs on the v2.5 i think they're plenty of wiggle room for experimentation.

In terms of the external LED lighting solution, we've had some issues with LED light refraction on our divers helmet mounted cameras, which cause some "flare". Moving the light, would most certainly help this. Perhaps, a shortened v2.5 battery tube, containing a/several 100mA LED arrays, could be mounted in the payload bay area? Assuming additional conductors are potted in the endcap, this should be possible??

Just out of interest, how many peripherals can you/have you slaved off of the I2C bus?

lihP


#7

The only fundamental limit is the capacitance on the bus, and the direct answer to your question is "a lot"

The near-term reason for bringing the I2C bus outside the vehicle is to support the depth sensor/compass/IMU module that we're working on. We've got prototypes put together, but the debugging is kind of on hold right now while we get the 2.5 kits out the door and properly documented.

-W


#8

This circuit could be an genius part of expansion of the openrov with a manipulator arm and extra lights:

http://www.adafruit.com/products/815

with pwm one can easily interface several servos, or pwm controll lights to dim.


#9

Hi Walt,

I'm looking at modifying my OpenROV(2.4) and my current design has 6 thrusters, a servo for the camera and then a servo and a small electric motor for a "grabber arm".

So the short question is can I run 9 things off the new board? And if not what is the limit?

Cheers,

Owen


#10

Hi Owen:

Yes, but it won't be entirely plug and play. There are pins provided for only six servo outputs, so you will have to plug the other three channels into the general-purpose I/O. If you are powering the "small electric motor" directly, without an ESC, then you can use one of the spare power PWM channels for that.

-Walt


#11

Thanks Walt,

Sounds like it can do what I want. The "small electric motor" was to drive a worm screw on a "pincer" but I'm thinking I might do it with a servo instead but I have no idea if a servo will work when wet. Has anyone tested it?


#12

Looking at the recent Dozuki instructions for 2.5 the ESCs get soldered onto pads on the board but there only seems to be room for three ESCs.

How would I go about adding extra ESCs for extra motors?

Thanks, Owen


#13

Hi Owen

If realestates’ quite tight, you may be able time mount an additional battery tube, in the payload area, containing the additional ESCs? This would require additional wires potting in the endcaps…

Phil


#14

Hi Phil,

It's actually the connections onto the board I'm thinking of. Are there only connections for 3 ESCs? Is there another way of attaching them? How many can the board support?

All this electronics stuff is greek to me :)


#15

Hi Owen:

Three ESCs mount directly to the circuit board. Any others you have in your design will have to be placed elsewhere inside the ROV.

While the electronics stuff may be greek to you, unfortunately it's part of the price of admission for designing your own ROV. If you're new to ROV design, I would recommend getting hold of the book "Underwater Robotics" by Moore, Bohm, and Jensen. It's expensive but well worth the money.

-W