So, this I think will be our EMERGENCY STOP arrangement. Whoever is in charge of the mowing mission, will need to wear this remote. Depressing either button will trigger the E-Stop relay in the mower shutting it down. The E-Stop relay will latch and need to be physically reset, at the mower, to regain operation.
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I have one as a cut off on my generator. I had a few fail until I added 12v regulator to
it to regulate the power as 14v+ from the charging output was too much for it.
Some really good progress RoverOne is performing quite well, a little more tuning needed maybe, but then again, tuning stats all over when the electronics gets transferred to the Beast.
We may start installing the interface stuff on the Beast (mower) next week. The Autopilot / FPV unit will be one detachable structure secured to the top of the roll-cage by four wingnuts. A single umbilical cable with a multi-pin aircraft style connector interfaces it to the Beast’s drive electronics. I like to keep my mods reversible, so a hidden slide-switch reverts the machine to as-bought operation.
Here is the form-factor design consideration for the Autopilot / FPV unit (yeah, I’m an old school SolidWorks10 and AutoCAD 2007 type, “Old Fart” that I am!) 
Pretty nice weatherproof connector I got on Amazon.
My dual version of John Harlow’s opto-isolated DAC (thanks John). I used sockets while I await the arrival of the chips next week.
The magic slide-switch that transforms between stock RC and RC / Autonomous.
Got my harnesses and 24V to 12V buck-converter all made up to simplify installation out at the flying field.
Some bits and bobs:
A peek inside the belly of the Beast:
All the motion electronics and battery as shown above, is below this deck
No longer using any Arduino conversions or interfacing. Control is native Pixhawk 6c Mini.
My machine shop and electronics lab (when it’s clean):
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Back to the build. Chassis and enclosure work this morning and flying this afternoon.
Chassis CNC laser cut from 1/8" black acrylic sheet and will be soft mounted with a foam underlay, to absorb shock. I suspect a bunch of other little internal fittings may be needed and these will be laser cut acrylic as much as possible.The PVC enclosures, lower is containment for all he autopilot electronics, top houses the GPS antenna and forward containment is the FPV camera and video transmitter.
Framework will be 1" aluminum tubing and CNC plasma cut 1/16" aluminum sheet. External hardware will be stainless steel.
Chassis layout, lots of room for wiring and for keeping power devices and wires away from the compasses. I am thinking the diversity RC receiver can go topside below the GPS antenna and the satellite receiver somewhere downstairs
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Nice work - you are flying along. I have a couple of questions/observations..
RTK but not RTK yaw ? - suggests you are relying upon compass for headings (or did i miss somethign) Brilliant if it works, but you have ICE motor, lots of metal and moving metal also. Your compass may need some tuning and calibration/offsets once you do some AUTO missions.
While you are waiting for any parts - have a good play around with SITL the emulator built into Mission Planner. Download the skid-steer model of the ROVER and practice building mow plans.
Do some failsafe planning - eg RC comms go down, telemetry goes down, mower is driving forwards but not moving, battery goes flat in the remote cut tx. Do some planning around GPS loosing accuracy eg RTK fix → 3D fix if you value your gardens, fences etc.
We put a bunch of effort into the ICE motor, as heavy grass would stall out the mower blade, im guessing your flail motor is more stall resistant.
Cheers !
I take it you are powering the op amp side of the DACs with the 5v available on the mower controller (I think it’s the bottom right connector shown on that diagram) otherwise it wouldn’t be isolated.
Also you might want to provide filtered ventilation to the electronics. In my case (pun intended) it can get quite dusty and hot.
Thanks guys, all noted and much appreciated.
I am relying on the compass because at the time of purchase, in my ignorance, I did not consider RTK YAW. Hopefully it works, the rig is going to be located on the roll-cage ~8" above and behind the engine. The engine is diesel, if that matters much, so I’m hoping to get away with it. We have yet to find something that stops the beast, so a separate Garage type remote will be another implemented E-Stop device in the first iteration.
Right now, we’re just trying to get it going and see what else we need to correct and implement. We have a ton of money and time invested in this thing already and lets not forget our $ is = US$0.14 
UPDATED LAYOUT
So, in the event the compass does not work out for us (really hoping it does), we just need to buy a second H-RTK NEO-F9P w/ Vertical Array Patch Antenna × 1 NEO-F9P UART / 40cm to implement RTK YAW?
In consideration of and preemptively, a little structural design change was done to move the electronics a bit farther back in an attempt to mitigate interference with the compasses.
