First basic connections of farm rover

Greetings, I am building a large four wheeled rover to carry things around my farm and my two main drive motors just arrived, so I am eager to get them spinning from an RC transmitter. I am brand new to micro-electronics, but I think I either have everything I need, or its in the mail, to have a first go at it. I wanted to make sure that I wasn’t missing any vital components, both so that I could lessen delays in the development and hopefully not fry any of my components. I’m hoping to test everything inside before I weld together a frame. This is what I have or have ordered:

2- 12V large automotive truck lead-acid batteries
Pixhawk 2.4.8
Pixhawk power module 5.3V BEC- up to 28V and 90 amps
2- 350W 24v BLDC in-hub scooter motors and their controllers (12" tires)
38N.m digital servo rated 24V and 10A w/magnetic encoding for a steering motor
a six circuit automotive distribution panel/fuse box
FRSky Q X7 and X8R receiver

My plan is to wire the batteries to the distribution panel and use three of the fused circuits to hook up the motor controllers for the two drive wheels and the steering servo. One question I have is whether I should put the Pixhawk Power module in-line with the main battery wires (like it looks like it was designed to do) or whether I should run it off a forth branch circuit.

I’m also not sure if the Pixhawks main ouputs to the three motor controllers will be powered by this set-up, or if I need to take care of that another way?

Are any circuit protection components missing, or is the BEC and some 10 and 15 amp fuses all I’ll need?

I went with the hub motors because I plan to build a frame without an axle, so that the rover can pass over beds of growing plants. If I understand correctly, the front wheel steering version of the rover code is designed around one drive motor. Will it be able to give my two motors the same instructions, so they function as one?

My biggest question is will these drive motors work. Their controller is for a scooter and it came with no documentation. After watching some youtube viedos for similar controllers, I believe one of the many wires coming out of it is for “throttle” and hopefully one of the others allows to to select reverse to select reverse.

I would also bash together a quick prototype out of scrap wood to test how it handles before welding.

I am building a smaller farm robot for spraying and have the power module in line with an XT60 connector so it can monitor the total current for everything (easier to check battery life).

Assuming you mean e.g. 5v low current to run whatever MCU is on the controller I think it depends. E.g. I have cytron controller that only needs a signal (has it’s own little regulator on board) but I think some controllers also need a regulated 5v input. Maybe I misunderstood your question though.

The PWM signal will be provided from the 5v input to the Pixhawk. You can also pull a small 5v current from the rail.

I have not bothered with RC as I only really plan to run autonomous missions. For playing around/testing I drive it via WiFi on my phone with QGroundControl android app (in Acro mode).

I think the fuses will be enough. For testing I am using disassembled cordless drill pack that I bypassed the current protection gubbins on and am not dead yet :smiley:

Yup, just connect both to the same throttle pin (split the cable) to send the same PWM to both. That sends the same instructions. However, it’s possible the motors respond slightly differently due to manufacturing variations. I have seen a thread on these forums with setup of throttle left/throttle right to give balanced speed (measured by an encoder) and still use servo steering but I can’t find it.

I guess yes but probably no one can answer for sure without more details of the controller.

1 Like