Hi,
To my knowledge you are correct, but I will need to know a bit more about the switch connections that he plans on using.

Martin.

Of you want to use a magnet, of course forget the Hall effect semiconductor, best, as appointed, is to use reed relays, looks a good idea to use a screw and a motor to remove the main fuse, place a second reed to make the motor put on place the fuse again

Hi, what sub are you building as i'm making magnetic power on/off switch if there space in the WTC.

cheers Tim

Fair comment.😉
Ciao, Doug 😎

While I accept you had that in mind not everyone would realise the situation. Stating the obvious needs to be done on occasions.

Hi Haverlock, Quite correct.
Nobody said it did!
We took it as read that for operation main power drive would be connected and disconnected at the end of the run. Preferably by removing a fuse in the positive lead.
Batteries should not be left connected in models anyway.😉
Cheers, Doug 😎

switching off and on via the ESC switch does NOT disconnect the battery from the ESC just stops the ESC passing current. Power is still being used. The only way to end all current flow is to disconnect the batter by either opening the pos or neg lead from the battery. Mounting the magnet on the end of a screw and having that fit into a threaded hole should deal with the problem of keeping it in place while running.

Absolutely Steve 👍
Alternative is to make a holder for the magnet to prevent it getting knocked off by weeds etc.
Also agree that any Failsafe' circuits must have an independent power supply.
Place to put the switch, or latching relay, is definitely in place of the little slide switch usually supplied on the ESC.
Just checked on some of my ESCs, Graupner and mTroniks, the red lead to the switch is NOT connected to the red lead supplying the RX and servos via the built in BEC. Guess the switch just triggers an FET switch inside the ESC. So the normal 500mA limit of reed switches will be enough. if a latching relay is used make sure the pull-in current is less than 500mA. Have fun All, cheers, Doug 😎
Eric; which sub is your mate building?
I have a Type 1A U-Boat dynamic diver, speed and planes only, and a kit for an Akula 2 which will be a static diver, with tank etc.

If the intention is to switch on with the magnet then remove it then you will need the reed switch already mentioned plus a latching relay.
In use you would apply the magnet which will switch the relay which in turn will switch the ESC. A second application of the magnet will unlatch the relay.

Possible choice of relay.
Relay https://www.ebay.co.uk/itm/5v-12v-24V-Coil-Bistable-Latching-Relay-DPDT-2A-30VDC-High-Quality/113232919274?hash=item1a5d353aea:m:mH8OjtWO_5VZ843iolIqa6A:rk:3:pf:0

He would need to consider carefully that he still has power to the safety backup which will blow ballast a certain time after loss of signal.

Steve

I do not know how much knowledge of electronics your friend has but I need to point out that a hall effect sensor is not like a relay. While they do act like a switch ( sort of) they need to be powered and have a hall effect voltage to switch. This would mean in the use intended there would be a current drain on the sensor and if the power supply ( battery?) voltage fell to far it would not function.
The effect you want could be replaced by a reed relay cheap and simple to use. However reed relays can only pass low currents so would need to be cascaded with a higher rated relay before switching the main battery supply on and off.

https://www.ebay.co.uk/itm/10-Pcs-2-5X14mm-3-Pin-4W-Glass-Reed-Relay-Magnetic-Switches-N-O-N-C-SPDT/372165424048?hash=item56a6c9b3b0:g:vgAAAOSwJtdaL2~p:rk:53:pf:0

these reed relays have both normally open and normally closed contacts and at a couple of quid for 10 worth buying so he can experiment.

Depends on how he has it wired up, is he using an Mtroniks esc? if so these have an on/off switch & bec, so he could replace this switch with the proximity one.