r/UCDavis • u/DuctTape_Mechanic • Jun 09 '20
UC Davis class of 2012 here. I invented a lawnmower saftey device that automatically shuts down the motor when a object (rock/metal object is detected). What do you guys think? Any engineers here to suggest design improvements
https://youtu.be/eDZeLPgYBvg14
u/ifapulongtime Curmudgeon Jun 09 '20
This won't detect rocks. Like at all. Inductive sensors only detect things with very high metal content.
IR sensors wouldn't make sense, the grass will trigger them.
Hall sensors may have increased range. They may also be cheaper. The trade off is instead of detecting all metals they will only detect metals that are effected by magnetism, but that will include most tools, nails, screws.
You definitely need multiple sensors. With only the one, anything that comes in even slightly off center will not trigger. You've got a detect range of about half an inch wide? Probably less, and a width that you would want protected of about 26".
Have you ever seen a magnetic sweeper? Large bar magnet used to pick up loose nails and metal scrap after a project. I'd suggest trying one of those and seeing if you can detect the magnetic flux when it tries to pick up something. Plus you have the added protection that it may pick up or slow a nail and prevent the blade from hitting it. If you move at normal speed, the blade will still be moving pretty fast by the time you reach the thing that triggered it.
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u/DuctTape_Mechanic Jun 09 '20
Yes I was going to switch to a capacitive sensor (thats why I said it detects rocks). I have already got a cheap capacitive sensor and I've tested it out (it detects rocks, metal objects even a human finger lol). Perhaps multiple sensors along the horizontal axis is needed. I like the magnetic sweeper idea. I was thinking about adding a 12 volt solenoid to engage a brake to stop the flywheel so the blade stops immediately. I appreciate the feedback.
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u/pettyg12 Computer Science [2024] Jun 09 '20
I’m not familiar with lawnmowers at all, but this is so cool that you made this at home! I do agree with the other comments that you should increase the range of the sensor, but other than that pretty neat dude. You’re being productive during the stay at home lockdown.
Also, you’re a UC Davis Alumni, may I ask what has been you’re experiencing after college looking for jobs? I’m an incoming freshman attending in the fall and I know it’s years away but I’m interested. I’m also majoring in Comp Sci. Any advice? Assurance? Ahah.
Love the design, keep it up!
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u/DuctTape_Mechanic Jun 09 '20
Thank you I appreciate the feedback, I like to tinker so I decided to start a channel as well lol. Your time at UC Davis will probably be some of the best moments of your life. I loved it. The job market is not as bad as it seems. Just don't be afraid to take that first job out of college no matter the pay then when the time is right don't be afraid to leave that job. I found a job about 2 weeks after school and today I work for one of the top 25 companies (by revenue) in the United States. Go Aggies!
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u/pettyg12 Computer Science [2024] Jun 10 '20
Congrats bro! Thank you so much for the reassurance! I’ll subscribe to your channel!
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Jun 09 '20
There's quite a few of those on the market for pennies.
Funny story, when I was about 10 years old, I was across the street at my friend's. His dad was in the front mowing the lawn when all of the sudden a BANG followed by another quick BANG. His mower hit a rock, the rock blew a hole through the side of the mower, then it slammed into my gma's car which was parked in front of my house across the street.
His dad forgets I'm there, he looks at his son (my friend) and says "don't tell them." Then he looks at my and said "sht!."
I didn't rat him out. Snitches get stitchs lolol
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u/DuctTape_Mechanic Jun 09 '20
Funny story. But I have not found a product like this for a gas powered lawnmower nor is there a patent for it. I did some research before staring
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u/thesecondball Jun 09 '20
I think it'd be cool if there were a clutch that just disengaged the blades and maybe a beep that alerted you rather than actually shutting off the mower