A few questions for Walt regarding supply currents and Wire size for the V2.5 Cape


#1

Hi Walt

With the new v2.5 Cape I see that you are using 2 pins for +vcc and 2 pins for grounds. I know that each pin on the 25pin connector can handle 5A so we could pass 10A through the two +VCC pins. What I don't know is how much current will be pulled from the batteries with all three motors running at full speed. The thrust charts done on the props indicated up to 9A on each motor could be drawn from the Battery. What has your testing shown for the current draw on the ROV in a max'd state? I will be using 4 Motors so the current draw will be higher but I will have to use other pins that may be available to source power to my 4th ESC so that should not be a problem.

The second Question is about wire. The DB25 can handle 20 Gauge wire and I was wondering what gauge wire you are now using on the OpenROV. Does the 18 gauge wire fit on the connector or did you switch to 20 gauge?

Regards

Dave


#2

I just noticed in the 2.5 Build instructions that you are now using 20 gauge wire so that answers my 2nd question.


#3

Hi David:

We're going to be doing our first open-water testing of the 2.5 vehicle this weekend, so check back sometime next week. I'll try to remember to make note of what kind of current we're drawing on the vehicle, while we're doing all the other tests we want to do.

I'm guessing that, when being run hard, there is more than 5A being pulled from each battery pack. I suspect it's not a serious issue as long as you don't do it continuously. Also note that if you have your ROV weighted correctly, the only time you would need to use a significant amount of thrust on the vertical motor is when you are descending at the start of a dive, or surfacing at the end of a dive.

If you want to bring significantly more power through the DB-25, I would suggest using some of the six spare pins for that purpose. If you are going to do that, I'd also solder copper wires directly to the pins on the DB-25 jack on the bottom of the PC board, since the traces that lead from the 6 spare pins (labelled as TP-20 through TP-25) were not really sized to handle 5A of current.

Hope this helps.

-W