[Dan] wanted to learn a bit about solid state ignition in engines; to get started he needed a test subject, so he decided he would upgrade his old 12 horsepower lawnmower.
Originally the lawnmower engine used a magneto coil ignition system, magnetos are simple and very common in lawnmowers. The magneto is designed to produce a high voltage spike when influenced by a magnetic field. A magnet is attached to the engine’s crankshaft to time the voltage spikes, these spikes are fed directly into the spark plugs to cause ignition, this is why you don’t need a battery. [Dan] explains how the solid state ignition works on his site as he goes through the build details. Essentially it uses a hall effect sensor to detect a spinning magnet on the crankshaft for timing, and a transistor and battery to fire the spark plugs for ignition.
Once he got his circuit up and running on a breadboard, he fitted the entire system into a neat plastic box and fixed it to the front of the lawnmower, as if it was meant to be there all along.
[shadeydave] wanted to build his own Lawnbot, but he had no idea where to start. He purchased some DIY plans online which looked like they would get the job done, but then he strayed from the path in a big way and spent gobs of money in the process.
In his Instructable writeup, he details each misstep he made, explaining why his choices were bad as well as how much each mistake cost him. It sounds like pretty much everything that could go wrong did go wrong, from spending money on unnecessary microcontrollers to choosing the wrong wheels. Our favorite part is where he mentions that he couldn’t figure out how to create a “kill switch” for the Lawnbot in the event that his transmitter loses contact with the speedy whirling death machine.
[shadeydave] is well aware of how poorly his build went, and primarily wrote it up as a cautionary tale to others out there who might decide to take on a similar project. He says that the Lawnbot works for the most part, but with his newfound wisdom he will be revising the bot, having learned from his mistakes.
We actually like to see this kind of writeup as they can be quite beneficial to someone trying to put together a similar project. So if you have some major flubs under your belt, don’t be shy about digging them out and letting us know. As Thomas Edison said, “I have not failed. I have just found 10,000 ways that won’t work.”
Continue reading to see a quick video tour of [shadeydave’s] mostly working Lawnbot.
[phantompinecone] has an electric mower that worked great for about 4 seasons, and then the battery started to die. A replacement was installed but it started being a pain after the first season. Since the battery was brand new (and probably costly too) there must be something else.
Checking the brushes, which were fine, the next logical place was the switch.These mowers are just a battery, motor, and switch. Yanking it apart there was indeed a problem, they were chewed up and corroded, not allowing full electrical contact. So [phantompinecone] replaced the simple mechanical switch with a MOSFET.
Electrically there is an IRF1405 MOSFET, some resistors to pull signals around and a couple diodes to A) keep the back emf from the motor in check, and B) drop the voltage going into the fet from 24volts to 12. Problem solved, and the motor should not have anymore trouble caused by a junked up switch.
There’s the quiet serenity of paddling through the backwoods in a canoe, and then there’s this. It’s a lawnmower motor powered canoe that comes complete with steering wheel, throttle, and a stereo system. To keep the craft balanced the driver rides in the front seat while the motor is hanging off the stern of the boat. The biggest trick is not swamping the thing while getting the motor running, but future plans do include adding an electric starter. There is a kill switch for safety and it appears that top speed will not cause any stability issues. It’s hard to tell for sure from the video after the break, but it sure does seem to be loud!
It’s no secret that we’re gear heads at heart. Our transportation hacks category is full of unfortunate machinery like [Steven Laurie]’s motor art, weed whacker bikes, and electric motorcycles of all types. Even we have trouble justifying the existence of this monster truck style lawn tractor though. We haven’t found a project site for it and can’t help but wonder what kind of person would build such a thing? It’s obviously the type that would own a car sized American flag. We just need to realize with the popularity of lawn mower racing, this sort of thing was bound to happen.
You will need a battery-powered lawnmower for this, as well as a 12-volt solar charger with a car lighter jack. This easy hack mainly involves a small amount of work with the wiring; the car lighter jack must be removed from the solar panel so that the wires can be attached to the batteries. Yeah, that’s it. We’d love to see a more elegant solution since the way it is now you have switch the wiring from parallel to series everytime you want to mow.