New member, New project

Ello. I’m building a pull behind mower to add additional cutting area to my riding mower, Another 48". I have a Mega 2560 laying around from an old attempted project, and I’m looking to integrate it into this pull behind. Push to start, Engine RPM, Deck RPM, Engine output Voltage(tested at battery) and Auto Kill if deck stalls or gets jammed and I do not notice it over the mower I am on. I think hall Effect for the two RPM sensors would suffice, as putting small IR sensors down where grass clippings will be can cause read issues. I would like the Arduino to start the engine(use Engine RPM for know when to let release starter). Basic Display will show Voltage, Engine RPM and Deck RPM. I do have a 3.1 TFT display but think a 20x4 would be more rugged/suited for this. the unit can be mounted on the Main pull motor then connect to pull behind via Serial cable.

What I think I Need:

20x4 Display
2 Relays, 1 for starter, 1 to kill coil pack power
2 Hall effect Sensors
Voltage stepdown for Arduino(I have this already)
Voltage Module(for sensing power of battery)
Switch for Arduino Push To Start

Does this sound like it will suffice?

Im asking very similar questions:

For knowing when the engine is started... Does your engine have an alternator or dyno with a charge warning light? or actually you could just take the voltage as indicator the engine is running (battery chargine = 14v+ = engine running - simpler than engine RPM).

Very happy to collaborate on the code for engine RPM as that is exactly what I am looking to do, but without any blocking.

I've been looking at frequency counter code to adapt but so far not found anything that fits the bill.

it does have a Warning light, but this only comes on above 30% throttle while running. so the Starter will drag to long for comfort. The engine is a 20HP Kohler Command 2 Cylinder, and its overkill for this set up. I may step it down to the 13hp that would suffice for the 48" deck, as I Do not have that engine yet I would like to not plan on using the voltage as a indicator for running as I do not know how it's charging circuit will be set up. I was thinking simple hall effect, magnet on one pulley down on deck, and the other could read the same magnet on the crank the coils use to fire. The project could easily suffice without Engine RPM, and start/kill functions, but it's Arduino, why not. the functions are there! lol

The only part of the project that I would be concerned about is the Arduino knowing when to shut off the starter motor. Is there any significant advantage in giving the Arduino control of that process rather than simply using a manual push-button switch completely separate from the Arduino?


I can live without it starting it. But the kill I really want to keep. I can measure starting RPM and always give it a set valve of 50 RPM above to for release of starter. I also want to start a "Autonomous Mower" project after this one using both boundary wire, and RTK or Differential GPS to mow 2.5 Acres. That's another subject though. But doing the mentioned above can give me experience for that project.

Sorry, I'm really confused about this bit:

The engine is a 20HP Kohler Command 2 Cylinder ... I may step it down to the 13hp that would suffice

You are gonna have to walk me through that bit, I can't get my head around that concept..? "Less Power" is completely alien to me? :wink: Haha!

well yeah ok now you put it like that, going off battery voltage is perhaps not a good idea.

Well seeing how a 13HP will suffice, the 20HP can be saved for that Harbor Fright 10K gen head I want to use :wink: Seeing as how a 13HP is cheaper and more easily obtained, it makes since. Right now though the 20HP is the one going to be used.

Well if you refer to my thread, there’s some ideas for counting revs on there, and on the other thread that is linked at the top of the thread I linked up there ^^^ if that makes sense?

I’m gonna have to draw a diagram to understand this “Less power” thing…

I have read through it, but need to go back and re-read as well as check the links inside of your thread. I am also thinking of mounting the Arduino on the rear mower, and just run a cat 5 with a waterproof connector for display and the Start/Stop switch. less wires to run between the two. The start/stop will more or less carry signal for Arduino to start and stop, not carry amp for the relay directly.

Thinking more, I may negate voltage monitoring for blade engagement, so 2 switches, one for Start/Stop of engine, one for Start/Stop of deck PTO Clutch(these are 12V)

so display will be like: While Running, RPM is for show

Engine: Running
Deck: Running
Engine RPM: 3000
Deck RPM: 400

While Towing:

Engine: Running
Deck: Off
Engine RPM: 3000
Deck RPM: 0

More, but you get the idea. This will fill the 20x4 display, so I may just place an LED light on the deck somewhere for non-Arduino monitored Charging. Also need Arduino to know when I start/stop the deck vers when I'm cutting and it gets jammed so it'll safety kill PTO and/or engine.


Engine: Running 13.8
Deck: Running
Engine RPM: 3000
Deck RPM: 400

Engine: Off 12.3
Deck: Off
Engine RPM: 0
Deck RPM: 0