Introduction and Getting Started

[seandepagnier]

Greetings,

My name is Adrian, and I have a 1982 Mason 43 cutter-rigged sloop, which we've owned for 23 years, and which currently resides on the Chesapeake Bay (VA, USA).  When we were about 20 years younger than today, we took our three kids cruising in the Caribbean and US East Coast (up to Maine), and explored the US East Coast and Caribbean for about 3 years.

welcome

I need to rig this thing up initially to get started, before I try to "harden" it into a final product.  Here are some questions that I think are all about "What are best practices?":

I'm sure you are aware already but just in case:
https://github.com/pypilot/workbook/wiki

• Should I buy stranded or solid hookup wires?  I'm thinking stranded, but maybe solid is good enough and easier?

Wow, no one even asks such questions. I dont know. stranded corrode sooner but it takes a long time. If there is a choice I would suggest stranded marine wiring that is tinned. If not: use whatever works.

Should I get ribbon cable(s)?  I recall seeing one picture with a ribbon cable that had the display mounted on a connector in the middle of the cable, and the MPU at the end (I think).  So, both GPIO connections on a single cable.

Should I buy a PCB board(s)?  What kind?

It is all up to you. I offer some products on my store that will save you this trouble. You can also study the designs and build your own.

Should I get special prototyping headers?  (I have male/male, but no special female connectors for the wires, so I can't use them as-is) 

The more non-soldered connections you introduce the lower reliability you will have. This is already an issue of the nokia5110 display which uses tabs pressing on the pcb and it last on average 2-3 years. I moved to jlx12864 screen.

Do I need more than the IBT-2 to drive my hydraulic ram? I'm basically not sure I understand enough about the concerns around this.  The wires that go to my motor are not that large -- I believe it's controlled by low-power solenoids, and the actual power supply is direct (i.e., doesn't go through the junction box) with a heavier gauge wire. As I write this, it occurs to me I have more research to do "in the field."

I'm thinking the interface point should be directly to the motor (i.e. the solenoids), rather than trying to patch into (and possibly destroying) the working J101 junction box.

I don't have a lot of confidence in the 43 amp rating. Even at the claimed 16 milliohms, the board would have to dissipate 30 watts which probably would require a fan.

It all depends on your motor and how hard it has to work. Beating upwind it may draw a lot more current to move in one direction. So for example if your worst case was 20 amps, then you likely need a significant heatsink. The heat generated goes up with square of current.

The IBT2 uses 7 and 9 milliohm mosfets. My high power controller uses 2.5milliohm mosfets and put 4 in parallel reducing the resistance < 1 milliohm. My controller does not need any heatsink or fan up to 30 amps. A less efficient controller is generally cheaper, doesnt last as long (heat kills components) and wastes more power as heat and has slightly reduced motor speed which means the motor also has to run longer.. and with slightly more delayed reaction which causes the autopilot to also correct a little bit more and therefore work slightly harder. So, even though it's may be only a few percent difference in top motor speed (7 milliohms is still quite good), the total power wasted compounds a bit more than that.

Should I prototype it using a breadboard (etc) initially prior to trying to build the "final product?"

To operate from the unit (not via my cell phone) what kind of buttons are recommended? 

Do you guys with successful builds have an emergency kill switch installed, in case you have an OMG moment ("Dang, my navigation is good - I clove that daymark in half!")

Adrian

If you have a clutch or bypass valve solenoid etc to engage, it is highly recommended to put a switch in series with this circuit so you can always regain manual control regardless of what the autopilot decides to do.