Thought the fuse was supposed to protect the switch not the other way round? - Page 1
Forum section: electronics / repair

author: bd139
author_rank: Super Contributor
timestamp: April 19, 2018, 12:35:39 pm
content: My Bosch lawn mower just blew up. Motor stalled. Totally incinerated the switch which went open before the fuse popped

author: Harb
author_rank: Regular Contributor
timestamp: April 19, 2018, 12:37:42 pm
content: Electric Mowers are for girls.....get a mans mower......get a mower you have to pull to start

author: bd139
author_rank: Super Contributor
timestamp: April 19, 2018, 12:39:38 pm
content: I would get one but my garden is so small I couldn't turn it around in it.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 19, 2018, 12:53:14 pm
content: Contacts probably wore down to nubbins, and were arcing the whole time -- hence why it didn't have enough torque to even start!Tim

author: Zucca
author_rank: Unknown
timestamp: April 19, 2018, 01:01:50 pm
content: After cleaning or replacing the switch, would some contact grease help here?

author: bd139
author_rank: Super Contributor
timestamp: April 19, 2018, 01:12:49 pm
content: Yep contacts toast. I took the switch to bits:

author: bd139
author_rank: Super Contributor
timestamp: April 19, 2018, 01:25:22 pm
content: They're awful. This one is about a year old. I was quite surprised to see that the wires are just push in and basically friction fit. Terrible design really.

author: Zucca
author_rank: Unknown
timestamp: April 19, 2018, 01:32:40 pm
content: same problem with a little light in a kid bedroom table. Switch was toasted, after some contact cleaning and replacing the light with a small power LED it`s all good now.no idea how long it will last...Anyway how to prevent the contact toast poblem? Grease or relais?I suppose as long the switch is in free air, there will be some O2 to burn and it will create the black burned stuff on the switch.

author: schmitt trigger
author_rank: Super Contributor
timestamp: April 19, 2018, 02:45:38 pm
content: Observation based on the limited info from the photo.It appears that the top right contact from the first actuator suffered the most, as the others contacts are only lightly charred.That to me indicates that the contact pressures were not evenly distributed.

author: Zucca
author_rank: Unknown
timestamp: April 19, 2018, 04:54:30 pm
content: Mah... The four contacts don't switch at the same time. I think that contact was the last one to touch the metal, so the arc was happening there by closing the circuit.

author: PChi
author_rank: Frequent Contributor
timestamp: April 19, 2018, 05:36:22 pm
content: Fuses are there to stop fires, nothing more.

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 20, 2018, 05:35:14 am
content: Quote from: Harb on April 19, 2018, 12:37:42 pmI know of a girl (Rinoa Super-Genius) who hacked together a propane powered mower. What was really entertaining was when she asked one of the guys to try to start it up... Largely because it was hacked together and several of the controls do not work as expected. Such a thing would definitely be too big for a tiny yard, where a manual reel mower would be ideal.

author: james_s
author_rank: Super Contributor
timestamp: April 20, 2018, 05:55:26 am
content: I have a B&D electric mower that the switch failed the same way, I replaced it with a mosfet and that worked until I upgraded the batteries to LiPo packs, the ESR was so low that the inrush popped the mosfet. I'm making a new control now using an attiny microcontroller to PWM soft start it, hopefully that'll work better. I used a gas mower for years but my yard is so small that it's ridiculous, I spend more time cleaning out the carburetor than I do mowing. Seems I'm always having to go get fresh gas too, for a small yard electric is hard to beat.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 20, 2018, 10:27:04 am
content: you'll learn pretty fast that fuses used in smps, motors, psus, are the last to go loll

author: bd139
author_rank: Super Contributor
timestamp: April 20, 2018, 10:41:05 am
content: Good news. New switch arrived next day from a random eBay seller. This one looks more robust. Now to stuff it in and finish the lawn off.

author: Cerebus
author_rank: Super Contributor
timestamp: April 20, 2018, 01:55:28 pm
content: Pah! Lawnmowers are for wimps, you need aDaisy Cutter!

author: bd139
author_rank: Super Contributor
timestamp: April 20, 2018, 02:54:10 pm
content: A couple of years ago there was a massive spider in the back garden. Something Australia sized but here in the UK. Not putting up with that kind of shit. So there is still a burn mark 5 feet across and no grass where that died via homebrew incendiary, so I'm totally up with the daisy cutter idea

author: james_s
author_rank: Super Contributor
timestamp: April 20, 2018, 06:15:33 pm
content: Usually about once a year I see an article in the news about a house that burned down after some guy tried using fire to kill a spider.

author: bd139
author_rank: Super Contributor
timestamp: April 20, 2018, 06:16:26 pm
content: Keep an eye on liveleak. Might be me next

author: metrologist
author_rank: Super Contributor
timestamp: April 20, 2018, 08:02:02 pm
content: If it fails again, manual push mower is very convenient for small areas...

author: bd139
author_rank: Super Contributor
timestamp: April 20, 2018, 08:09:25 pm
content: Too many ant hills for thatI am a bad lawn keeper!

author: Cerebus
author_rank: Super Contributor
timestamp: April 20, 2018, 09:25:56 pm
content: Sounds like you're ready for Redimix to call. Added bonus, if you put enough steel reinforcement in first it'll offer a lovely ground plane at RF.

author: bd139
author_rank: Super Contributor
timestamp: April 20, 2018, 09:45:23 pm
content: Yes not a bad idea. I did think about writing "shit" or something in it with Roundup to accelerate the decision as well