Remote switch

[Roman]

Hi all,

Here's a query regarding a new project:

I am thinking of developing a switch that will be controlled mechanically by a remote actuator. A relay is not an option because the switch must be on at all times (except in emergency when it will cut off all current supply to the vehicle) without causing battery drain.

In other words, the body of the switch and the knob for switching it on and off are to be separated. This is because the switched wires have to be as short as possible, but the controls are to be placed at the back of the vehicle. The distance between the two will be greater than 3 meters.

I have some ideas how to do it but was wondering if anyone has seen such a thing ready made, just to to save me the time and effort?

[dollythelw]

yes - a friend has one on his comp safari racer - E stop with an additional cable operated actuator on the outside of the vehicle - I can try and find out where he got it from if it helps?

[BogMonster]

I would think something like one of the little square solenoids that you sometimes find as starter solenoids on Lister type generators may be worth checking out. I am not sure if these have a "normally open" and "normally closed" terminal, it may only be "normally open" but it would be worth a look anyway. If there is a "normally closed" terminal then your battery wiring could run through this and then when you flip the panic switch, then it would cut off power. Just a thought.

Otherwise you could have a cunning solenoid operated pair of wire cutters on the positive battery lead, press a button, snip, all power is cut off

[Diff]

Hi all,

Here's a query regarding a new project:

I am thinking of developing a switch that will be controlled mechanically by a remote actuator. A relay is not an option because the switch must be on at all times (except in emergency when it will cut off all current supply to the vehicle) without causing battery drain.

In other words, the body of the switch and the knob for switching it on and off are to be separated. This is because the switched wires have to be as short as possible, but the controls are to placed at the back of the vehicle. The distance between the two will greater than 3 meters.

I have some ideas how to do it but was wondering if anyone has seen such a thing ready made, just to to save me the time and effort?

I used a simple system on my trials buggies, so that that the emergency cut off could be actuated from either side of the vehicle. A simple 'red key' type cut off is fitted wherever you like and you run a bowden cable with a knob (eg carb choke cable) to wherever else you want. The end of the cable goes through the hole in the tab/handle of the red key. You put a simple barrel nipple on the cable end and arrange for the cable to pull on the key such that when you pull the cable knob, the key turns through 90 degrees and pops up, cutting the electrics. The key switch can still be disconnected in its original location too.

Regards,

Diff

[Andy]

Otherwise you could have a cunning solenoid operated pair of wire cutters on the positive battery lead, press a button, snip, all power is cut off

brilliant, possibly too much maintainance keeping the cutters sharp though?

[landmannnn]

The ideal switch is called a self latching relay. These relays use no power once switched on or off, either using magnets or a mechanical mechanism to hold the contacts in place.

An internet search will tell you all about it.

A specialised item so not cheap, last time I looked - over £120.

[Roman]

yes - a friend has one on his comp safari racer - E stop with an additional cable operated actuator on the outside of the vehicle - I can try and find out where he got it from if it helps?

dollythelw,

Thanks, that would certainly help. It may be just what I'm thinking of.

[Roman]

The ideal switch is called a self latching relay. These relays use no power once switched on or off, either using magnets or a mechanical mechanism to hold the contacts in place.

landmannnn,

Thanks. A latching relay could be an option, but the trouble is when you press a button to disconnect all power supply, the relay will not work because the contacts that supply power from battery (hence to its coil) will be opening at the sime time.

[rtbarton]

You could have a normally open relay permanently energised (therefore closed) through normally closed contacts on your emergency button (or buttons wired in series). Pushing one breaks the circuit and the relay drops, cutting off the power.

If you're worried about a relay being permanenttly energised used "economy contacts". These connect a resistor in series with the coil to reduce the current slightly. This works because the holding current is less than the picking current.

[landmannnn]

landmannnn,

Thanks. A latching relay could be an option, but the trouble is when you press a button to disconnect all power supply, the relay will not work because the contacts that supply power from battery (hence to its coil) will be opening at the sime time.

You are right that could be problem. Some mechanical types are spring loaded so that when you press the off button the relay is unlatched so drops out even though there is no circuit remaining.