need a switch that will deactivate with man overboard

[Madsalts]

I have a trolling motor hooked up to a canoe. I need a "dead man's switch" to de-energize the motor if I should fall overboard. This isn't being hooked to the power supply, but rather to a PWM, so current and voltage are low. I have a reed switch, but see a disadvantage: to make it work, I must attach a piece of ferrous metal between it and a magnet, otherwise it won't have enough strength to hold a magnet. By doing this for five hours (or more) at a time, many times, I'm concerned that the metal attached to the magnet will itself become magnetized, thus not breaking contact once the magnet is removed.

One option I'm thinking of is a switch that incorporates a metal rod that, when removed, opens the switch. I had something like this on a model rocket launch control years ago, and it was a bit dodgy. I wonder if better versions of it exist. What would such a switch be called?

Any other ideas? I'm thinking string tied to a knife switch, though this isn't ideal (the switch could close again during capsize).

Thanks.

 

[CDRIVE]

I bought this Electronic Bike Horn for my bike. While I don't consider the horn itself to be water proof the horn's thumb switch is. You can see the details of the thumb switch in the photos. It's completely molded in rubber on the end of the coiled cable. It would probably mount to your throttle as easily as my handlebars. Cannibalizing the switch from the horn is easy;.. only a few screws to remove.

On the other hand we may have members that know a supplier of the switch itself. Hell, they might be on fleebay too!

Chris

 

[AnalogKid]

On many speedboats with an ignition switch there is a pull-tab dead man switch near it. Insert tab, ignition switch works. Remove tab, engine dies. For some unknown reason, the same thing is built into my snow blower. Buy or build something similar, and tie the tab to your butt with string.

ak

 

[Alec_t]

The reed-switch would also do the job. Forget the bit of metal. Just tie the magnet to a pull cord. Magnet next to reed, switch contacts close. Magnet pulled away, contacts open.

 

[KJ6EAD]

Are we avoiding the readily available commercial off-the-shelf products for a reason? Too easy, don't want to be too safe, or what?

http://www.iboats.com/Emergency-Boat-Kill-Switches-Lanyards/dm/view_id.216623

http://www.westmarine.com/search?text=cut+off+switch

 

[CDRIVE]

Are we avoiding the readily available commercial off-the-shelf products for a reason? Too easy, don't want to be too safe, or what?

http://www.iboats.com/Emergency-Boat-Kill-Switches-Lanyards/dm/view_id.216623

http://www.westmarine.com/search?text=cut+off+switch

Uh, yeah. That makes more sense.

Chris

 

[Madsalts]

thanks for the replies. The commercially available switches seem to have poor reviews, stating that if used several times, the switch would likely break. I don't know if this is the case, and I hope to never be in a position where the switch is actually pulled, but I'd like to use something that isn't junk.

As for "not using the piece of metal", I have to with my switch. The reed has so little mass that even a pretty hefty neodymium won't hold to it. With the metal added, it works, though. I'm surprised that there isn't a switch that opens when a pin is pulled.

One thing that occurs to me is that I can use a DC connecting barrel jack/plug. I can wire the + and - of the jack in line with one wire, and then short the plug. When the plug is in, it will be closed. When out, it will be open.

 

[davenn]

I'm surprised that there isn't a switch that opens when a pin is pulled.

did you not bother to look at the links that KJ6EAD gave a couple of posts ago ??

that's the way most of them work!!

this style of switch is used in their 1000's on marine jet skis and the ones on the snow

I really don't see what your problem is ?

 

[Madsalts]

My mistake. I checked out the first link, and saw the same item that I saw elsewhere. On the second link, I see a lot more variety. I'll go w/ one of those.

 

[Kenneth Tan]

Reading this thread my thoughts were:
You need a switch that only activates if there is a unreasonable distance between you and the boat.
Giving you the freedom of movement while driving, while not being so precise that the motor might cut-off at an unwanted moment.
The solution is the simple lanyard with a spring operated switch. As seen on all small vessels.
It breaks the primary power to the engine. Simple, cheap.

 

[CDRIVE]

Reading this thread my thoughts were:
You need a switch that only activates if there is a unreasonable distance between you and the boat.
Giving you the freedom of movement while driving, while not being so precise that the motor might cut-off at an unwanted moment.
The solution is the simple lanyard with a spring operated switch. As seen on all small vessels.
It breaks the primary power to the engine. Simple, cheap.

Actually, if one dissects parts this post it's quite funny. I like the bold sentence the best!

Chris

 

[Kenneth Tan]

Reading it in bold, it's quite a funny line.
But it seemed very important to me because people were talking about using read switches. They are very distance sensitive. That's why I came up with that "one-liner"

 

[CDRIVE]

You need a switch that only activates if there is a unreasonable distance between you and the boat.

Well, "unreasonable distance from the boat" implies the pilot is not on board. If the pilot is not on board then any distance is unreasonable. Or is hanging off the gunnels OK? After all, he's not that far from being on board.

Here's hoping you take this with the humor that was intended. I couldn't resist the temptation!

Chris

 

[Kenneth Tan]

What's life if you can't laugh at your own mistakes.

 

[CDRIVE]

What's life if you can't laugh at your own mistakes.

My guess is that you meant to say "Some reasonable distance from the throttle". I'm not sure if that's a good idea either but In any case we had good fun!

BTW: You can ask anyone here on EP and they will assure you that I NEVER make missteaks!! ... EVER!!!!

Chris

 

[Kenneth Tan]

Neever?