# Remote lightswitch operation

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#### peterlonz

##### New Member
Hi,
I have an annoying problem with the lightswitch in my loungeroom.
There is only one switch which happens to be way across the room in an infrequently accessed position.
I could wire in a second switch but that would involve a great deal of wall damage routing the ac supply, requiring subsequent repair.

I thought a reasonable alternative would be to use an old TV IR remote to activate the existing switch. That would require an IR sensing device be fitted behind the existing switch, which I had considering powering with a modified "wallwart" secreted within the timber framed drywall.
Unfortunately the lightswitch will probably not be operated sufficiently to justify the always on power loss of the set-up I propose.
Anyone have a better idea other than "just put up with what's there."
Possibly I over estimate the wasted power of the always on sensing circuit?
All comments including the humerous ones appreciated, thanks

#### Mike_2545

##### Super Moderator
Look up X-10 home automation.

#### MikeMl

##### Well-Known Member
As for worrying about "all-ways on" power consumption of a wall-wart, here is the test I would do. Load the wall-wart with a dummy resistor load so that the resistor current is comparable to what your eventual circuit will draw (few mA). Plug in the wall-wart and leave it plugged in for 24hours. Come back and feel the wall-wart. If it is stinking hot, don't use it. If it is barely warm, then it is good to go because it's power consumption is a Watt or less.

Where I live, electric power costs about $0.09/kWh, so in one year, my wall-wart would cost (1*365*24/1000)*0.09 =$0.70 to operate....

Also, look for no-longer needed cell phone chargers. They are typically rated 5V @ 300mA. They usually produce no detectable heat if left plugged in...

#### peterlonz

##### New Member
power consumption always on wallwart

Thanks Mike,
I feel a bit of a goof for not thinking to do the simple calc.
In Australia we are bombarded with TV ads telling us to turn off all devices "at the wall" & it's claimed this could save up to 10% on power bills.
Whilst I consider this rubbish I guess it has got to me subliminally.
It would be well worth a dollar a year to have the convenience & also the satisfaction of having done this myself.
I have a few old Nokia wallwarts rated 3.7V at 35 mA but I suspect that's a lower voltage than is ideal, I will hunt around for an old 4.5 or 5 V unit a see how hot they get always on, usually they are warm to touch.
Any ideas how I can get AC power into the guts of one of these. I had planned to cut off the 3 socket prongs, but I think now there's a better way, even if I have to pot an external connection with epoxy & save posssible damage when getting inside.
Thanks again,
Pete

#### BrownOut

##### Banned
If you can shoehorn in a small relay, you can then run a pair of low-voltage wires under your carpet, behind furnature, etc. and hook up to a small switch to energize the realy. The realy will draw a little current, but only when the appliance is on. If it's only on a few hours per day, it won't draw any power for the majority of the time.

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#### MikeMl

##### Well-Known Member
...
Any ideas how I can get AC power into the guts of one of these. I had planned to cut off the 3 socket prongs, but I think now there's a better way, even if I have to pot an external connection with epoxy & save posssible damage when getting inside.
Thanks again,
Pete

I built an AC powered heater temperature controller into an aluminum mini box. It switched the AC line on/off to a 1000W external heater. I needed a little DC supply inside the box to power some opamps and stuff, so I just mounted a small wall wart inside the box. I left the prongs on; just soldered directly to them, and then slid some heat shrink over them. The wall wart sort of created a "bulkhead" inside the box such that all of the AC wiring was at one end, and the low-voltage wiring was at the other end of the box.

#### peterlonz

##### New Member
Mike ML
Again Thanks, yes I had considered that but I have to get this unit inside the drywall & I think this approach with an "outer box" will likely be too bulky. I don't like the idea of just relying on heat shrink over the "prongs" either.
As it happens I found a wallwart in my vast collection that comes apart after you defeat the 4 "security" screws (about 15 secs work). The prongs can then easily be removed & direct access to the guts is easy.
Only problem is its only 3V at 350 mA & I can't locate IR receiver module that operates at that voltage.

To Brownout,
Good idea & probably an optimum solution if I could get the low voltage wires down the wall relatively invisibly. Unfortunately the switch is exposed so that's not an easthetic solution (whats that about spellling?).

##### New Member
peterlonz said:
All comments including the humerous ones appreciated, thanks

Ah, I take it you had a good look around before joining the forums . Hope you enjoy posting here, by the way

peterlonz said:
4 "security" screws

Out of interest, were they normal screws or are you talking about those evil anti-tamper screws which require triangular or star-shaped insertions? I finally managed to fish out a star-shaped set from somewhere (I forget the official name) but those triangular ones still allude me.

peterlonz said:
easthetic solution

What's that you say? An aesthetic solution?

peterlonz said:
Only problem is its only 3V at 350 mA & I can't locate IR receiver module that operates at that voltage.

I only have a couple of salvaged wallwarts at the moment, but so far mine have come from a set of speakers, a lamp, and somewhere else, I forget. Check around, see if you have any other low-power devices which are broken / no longer needed etc; phone charger isn't the only option.

Since you're dismantling the wall wart anyway, maybe you should just use a separate transformer and bridge rectifier; you could keep it in the remains of the wallwart for insulation. I was experimenting with a lamp transformer which delivered about 10V recently.

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#### MikeMl

##### Well-Known Member
...
As it happens I found a wallwart in my vast collection that comes apart after you defeat the 4 "security" screws (about 15 secs work). The prongs can then easily be removed & direct access to the guts is easy.
Only problem is its only 3V at 350 mA & I can't locate IR receiver module that operates at that voltage.
...

Since your IR receiver only takes a few ma, consider reworking the transformer you extracted from the wall-wart to include a "Voltage Doubler" (two rectifier, two capacitor) circuit.

btw- I am a wall-wart collector. I probably have 50 of these things in a couple of boxes. I buy them at garage sales for $0.25 or so. I have AC ones, DC ones with and without filtering, I have regulated ones, I have newer ones that include a SMPS. My goal in life is to have the right junk on hand to build almost anything without getting UPS involved Last edited: #### giftiger_wunsch ##### New Member My goal in life is to have the right junk on hand to build almost anything without getting UPS involved Preparing for nuclear war there? #### peterlonz ##### New Member Lousy spelling & humour go together?? Thanks for the many replies & suggestions. About tamper proof security screws: I make it my mission to quickly defeat anything the Bas...ds throw at me. I modify old screwdrivers I would not be seen dead using ordinarily, I beat into shape stainless wire (it quickly work hardens) & then file to size etc, the triangular socket drive are some of the easiest because you can usually find an existing good condition screwdriver that will just force in & bingo all over Rover. I also have a pack of security screw inserts, but often when inserted into a holder they will not penetrate deep enough. BTW the star drive jobbies are calles "Torx" (I think) & they are pretty hi torque fasteners so its a great idea to have a specialised set of drivers for these. I think now my best option is to saw open a 12V wallwart, remove or saw off the AC prongs if necessary (one at least in my collection uses a short AC flexible lead which looks convenient). I'll try & figure out a simple circuit now but I'm not so hot at these tasks, its likely to take me hours in spite I know in principle whats needed. Pete #### audioguru ##### Well-Known Member Most Helpful Member An IR remote control is available that remotely turns on and off a light and dims it. #### peterlonz ##### New Member The best I found was a US$24 plus P&P assembled kit.
It looked pretty well made & reasonavle value but was not housed.
I figure I can, & should build one myself, even if I make hard work of it.
Still I'd be interested if you can provide me with a link to the unit you have in mind.
BTW I need 230VAC switching capability.
Pete

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