Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Remote lightswitch operation

Status
Not open for further replies.

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
 

MikeMl

Well-Known Member
Most Helpful 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.
 
Last edited:

MikeMl

Well-Known Member
Most Helpful 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?).
 

giftiger_wunsch

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 :p. Hope you enjoy posting here, by the way :D

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.
 
Last edited:

MikeMl

Well-Known Member
Most Helpful 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:

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
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top