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Lights on a keyfob (3 way switching?)


Mohsen

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So I have some bulkhead lights, on the fore and stern decks. These lights are operated internally via a switch. Pretty standard stuff...

What I would like to do is switch them on via a keyfob, such as this.

https://m.ebay.co.uk/itm/400764241561?_mwBanner=1

Easy right?

But I want to retain the ability to switch them on from switches inside. I haven't found any of these fobs with 3 way switching, L1,L2, COM, etc like you can get on an ordinary switch.

Is there another way to make this work?

 

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You need one with a double throw relay, ie both NO and NC contacts. I'll have a look...

Oh but also, the relay will stay energised in one of the states, so if say you turn it on with the relay then off with the switch, the relay remains powered indefinitely. Perhaps it would be easier to get another couple of keyfobs and stick them on the wall next to the switches?

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5 minutes ago, nicknorman said:

You need one with a double throw relay, ie both NO and NC contacts. I'll have a look...

Oh but also, the relay will stay energised in one of the states, so if say you turn it on with the relay then off with the switch, the relay remains powered indefinitely. Perhaps it would be easier to get another couple of keyfobs and stick them on the wall next to the switches?

Cheers Nick,

How much draw would the relay take when permentantly energised? I don't understand your last sentence, do you mean install extra lights controlled by the fob alone?

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8 hours ago, Mohsen said:

Cheers Nick,

How much draw would the relay take when permentantly energised? I don't understand your last sentence, do you mean install extra lights controlled by the fob alone?

I meant use the existing light but have no switches (that you use, anyway) and control the light with one of those relay units and two keyfobs, one in your pocket and one stuck on the wall near where the switch is now.

8 hours ago, Mohsen said:

Cheers for the link 6ma, might be a worthy price to pay as it would make my Mrs feel a lot better.

 

It talks about 140mA with "all relays operating" and the data sheet is for models with up 3 relays. So I think we could say around 50 mA for one relay, which I suppose isn't a lot.

51 minutes ago, Sir Nibble said:

How about an old Volkswagen headlight relay, change over on just a brief pulse with no standing current draw.

Yes, good idea but the ordinary light switch would have to be replaced with a push button or other momentary-action switch.

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8 hours ago, nicknorman said:

Perhaps it would be easier to get another couple of keyfobs and stick them on the wall next to the switches?

When the daughter was very small (a long time ago, she's now an engineering student and nearly as tall as me), she reached the stage at which she could take herself to the loo on the boat in the night, but couldn't reach the switch on the bathroom ceiling light ). Rather than hack about a lot of woodwork to run wires to a low level switch, I used a remote controlled relay kit and fob from Velleman. The relay board is hidden in the roof space alongside the light, the fob is hidden in the existing false back of a cupboard, and I soldered a couple of thin wires to it for a bell push.

The relay is only energised when the light is on, the receiver quiescent current with the light off is a few tens of milliamps. The fob battery has lasted for years. I think the exact kit has been discontinued now, but they have similar ones. The thing to watch with more modern digital stuff is that the receiver may paired to recognise only a specific fob (mine would work with any fob, or any number of fobs, of the same type), so you would need to check that it can be used with multiple fobs. The other thing to watch is quiescent current.

The other way you might do this with the relay you suggest, is to run a second live to the light fitting, switched by the relay, assuming yu can get at the wiring route. That way the relay need onky be energised when the light is switched on via the fob, the rest of the time the existing switches work as normal.

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1 minute ago, AndrewIC said:

When the daughter was very small (a long time ago, she's now an engineering student and nearly as tall as me), she reached the stage at which she could take herself to the loo on the boat in the night, but couldn't reach the switch on the bathroom ceiling light ). Rather than hack about a lot of woodwork to run wires to a low level switch, I used a remote controlled relay kit and fob from Velleman. The relay board is hidden in the roof space alongside the light, the fob is hidden in the existing false back of a cupboard, and I soldered a couple of thin wires to it for a bell push.

The relay is only energised when the light is on, the receiver quiescent current with the light off is a few tens of milliamps. The fob battery has lasted for years. I think the exact kit has been discontinued now, but they have similar ones. The thing to watch with more modern digital stuff is that the receiver may paired to recognise only a specific fob (mine would work with any fob, or any number of fobs, of the same type), so you would need to check that it can be used with multiple fobs. The other thing to watch is quiescent current.

The other way you might do this with the relay you suggest, is to run a second live to the light fitting, switched by the relay, assuming yu can get at the wiring route. That way the relay need onky be energised when the light is switched on via the fob, the rest of the time the existing switches work as normal.

Yes I think this could be a sensible approach but it depends on exactly what the OP wants it to do. If he only wants to be able to turn the light on and off using the remote, whilst it is off at the wall switch, then putting the relay in parallel with the switch will do that. But if he wants to be able to put the light on with the switch, then off with the keyfob, he needs 3 way switching.

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9 hours ago, nicknorman said:

Yes I think this could be a sensible approach but it depends on exactly what the OP wants it to do. If he only wants to be able to turn the light on and off using the remote, whilst it is off at the wall switch, then putting the relay in parallel with the switch will do that. But if he wants to be able to put the light on with the switch, then off with the keyfob, he needs 3 way switching.

True. If we're talking true domestic style 3-way switching, it would be possible to wire up a DPDT relay as an intermediate switch, but then the problem of the relay being energised a lot of the time remains.

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1 hour ago, AndrewIC said:

True. If we're talking true domestic style 3-way switching, it would be possible to wire up a DPDT relay as an intermediate switch, but then the problem of the relay being energised a lot of the time remains.

A latching relay would avoid that but as Nick has already pointed out that would require the existing switches to be changed to momentary. 

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33 minutes ago, nicknorman said:

Anyway, it is topics like this that remind me how glad I am I insisted on our Empirbus system for Telemachus. Makes this sort of thing a doddle to implement!

I thought light switching was the butler’s job...

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You need to use latching relays with normally open and normally closed or changeover contacts. These are available either with magnetic latching and have 2 coils  or with a ratchet single coil pulse type so do not draw power continuously.  Made by Finder or Omron either din rail or 11 pin base. Not designed for switching DC loads so use these to switch an automotive type relay for the load with a back emf diode across the relay coil. Contact if you need circuit/part numbers.

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44 minutes ago, adrianh said:

You need to use latching relays with normally open and normally closed or changeover contacts. These are available either with magnetic latching and have 2 coils  or with a ratchet single coil pulse type so do not draw power continuously.  Made by Finder or Omron either din rail or 11 pin base. Not designed for switching DC loads so use these to switch an automotive type relay for the load with a back emf diode across the relay coil. Contact if you need circuit/part numbers.

As previously discussed in this thread, that would require changing the existing switches to momentary. 

There are plenty of latching relays rated for 12V. 

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