An extraordinary light switch

[Boncuk]

Ok so you want to make a better switch.
1. The problem starts with powering it. It would be a real dogs breakfast to have a cord coming out of the lightswitch going to a wall adapter so you need to find a teeny weeny power supply that can fit inside the wall plate.

I don't see a problem powering a mixed voltage device in a wall outlet. The circuit would normally require +12V (for the bistable relay which is not available for lower coil voltages.) I split the power supply to -5V and +6.5V to power the MCU and the relay with limited voltage (11.5V). I also don't see a problem using a separate PVC pipe for a low voltage cable to supply the circuit.

2. Who's got 12 light switches in a row in their home?

It's a matter of room count. Of course, if your home has just one room one light switch might suffice.

3. Projects involving the mains are not suited for beginners or noobs, you would also run into local certifications so it wouldn't be easy to export as a kit. Transformer-less supplies also tend to run hot, plus their probably a bad idea when combined with a metal touchplate.

Connecting the mains side of the switch is nothing else than connecting a "normal" light switch with the difference that mains neutral can be connected to the PCB or directly to the light.

I also stated already that I don't intend to use a transformer-less power supply for safety considerations.

I never mentioned to sell the circuit as a kit, but publish it 'open source' as suggested by bryan1.

4. Efficiency, well a mechanical switch is pretty near 100% efficient, a touchswitch is not.

Admitted, a mechanical switch is 100% efficient not consuming any power, except when the switch resistance increases due to burnt contacts. The entire circuit (without LEDs) consumes about 60mW in standby and 500mW for a brief moment (when the relay is energized).

I guess having two LEDs illuminate the touch area will be cheaper than new wallpapers, since dirty hands will cause visible (and ugly) color changes around the light switch when searching for it in the dark.

5. Light switch manufactures in Thailand must enjoy selling to an audience that busts their stuff. It's possible to make an unbreakable light switch by mere mortals, it would probably cost less than a hi tech solution. Cheap light switches here are less than $1 retail, wholesale must be pennies.

Not only light switch manufacturers, but every electric and electronic manufacturer enjoys selling his stuff in Thailand. For an example, my lovely little stepdaughter has managed to push all control buttons inside the enclosure of her stereo. They are still working by poking a toothpick through the holes to hit the buttons.

My neighbor switches TV channels using grip pliers after having ripped apart the big knob.

6. Such stuff already exists. And there are oodles of em.
**broken link removed**

Not a good example! On top of the page it says "DISCONTINUED"

Last not least, I invited forum members to suggest improvement - not talk into me to use a better quality mechanical light switch.

Regards

Boncuk

 

[blueroomelectronics]

1. Don't use a bipolar relay, use a dual coil as they exist in 5V versions.
2. I've never seen more than a handful of light switches in a row in a typical home here in Canada.
3. Either way powering the project is going to be tricky, an external wall wart would be IMO a kludge. Tiny solar cell maybe?
4. Efficiency is becoming more important in a world hopefully going green. The wall wart will also consume power. As for seeing light switches in the dark you can buy neon lit switches.
5. Can't help with your stereo and kids, maybe mount it out of reach. I never busted my parents stuff when I was a kid, maybe a plate or glass on occasion. Seriously if folks are busting light switches their using it wrong.
5a. You still have knobs on TVs and the internet at the same time! Do the computers have knobs too?
6. Oh contraire; it's an excellent example. Discontinued = no demand or poor sales. It was very similar in function to your proposed design. I could find a currently made device with a little Googling.

As for improvements: solve the power supply problem first. Second use a 5V dual coil latching relay and don't use a split supply. Third it might be possible to use the comparator inside the PIC and get rid of the IC comparator. What's the purpose of the cap between mains & ground?

 

[Boncuk]

1. Don't use a bipolar relay, use a dual coil as they exist in 5V versions.

That's one improvement already. Thanks

2. I've never seen more than a handful of light switches in a row in a typical home here in Canada.

If using that kind of switch it will certainly make a better impression if the same kind is used all over the house. My house has eight rooms including the house management room, a guest room and a workroom.

3. Either way powering the project is going to be tricky, an external wall wart would be IMO a kludge. Tiny solar cell maybe?

I'll redesign the power supply after having sourced the proper bistable relay. It should fit into the wall outlet as well since the depth of the wall outlet is 1.5".

4. Efficiency is becoming more important in a world hopefully going green. The wall wart will also consume power. As for seeing light switches in the dark you can buy neon lit switches.

No objections here. May be I'll use solar power which is planned to be used for garden illumination.

5. Can't help with your stereo and kids, maybe mount it out of reach. I never busted my parents stuff when I was a kid, maybe a plate or glass on occasion. Seriously if folks are busting light switches their using it wrong.
5a. You still have knobs on TVs and the internet at the same time! Do the computers have knobs too?

Computers have no knobs, but buttons for the ON/OFF switch and the RESET button. That one has disappeared on my stepdaughter's PC.

6. Oh contraire; it's an excellent example. Discontinued = no demand or poor sales. It was very similar in function to your proposed design. I could find a currently made device with a little Googling.

I guess that circuit works using an IR illuminator and receiver, similar to automatic urinal flushing circuits. I didn't see any price for it. May be it is simply too expensive.

As for improvements: solve the power supply problem first. Second use a 5V dual coil latching relay and don't use a split supply. Third it might be possible to use the comparator inside the PIC and get rid of the IC comparator. What's the purpose of the cap between mains & ground?

Going for the suggestions. The cap between PE and circuit ground takes care of extra hum to be "injected" into the circuit besides the change of capacitance for higher reliability. The circuit won't work properly if battery operated.

Boncuk

 

[3v0]

A large part of engineering is to know the difference between what you can buy vrs what you need to build.

These should be looked at

Microchip mTouch
Cypress CapSense
Silicon labs QuickSense

There may be more out there. I would expect TI and National to have an offering.

 

[blueroomelectronics]

There are still a handful of IR light switches available. Lutron makes a popular one. About $40 to $45 US.
Remote control light dimmer switches - RANIA® IR - LUTRON ELECTRONICS

X10 has been making remote light switches since the 1970's, the modules are cheap ~$20 or less as it's unreliable crap.

 

[Boncuk]

Another approach

I guess capacitive sensors are too complicated for a light switch and changed the design completely to employ a reflective IR sensor Vishay TCND5000.

I left the additional functions (remote IR and push button operation) of the original design.

The Vishay TCND5000 has a daylight filter and works from 2 to 25mm with peak operation distance of 6mm and 20% collector current at 25mm.

I also changed the relay for a Panasonic DK series with two coils.

The power supply will be integrated in each individual switch with the power supply and the control circuit mounted as sandwich in the wall outlet box.

Here is the schematic design.

Boncuk

 

[blueroomelectronics]

Have you got a power supply in mind?

 

[atferrari]

Hola Hans,

By reading the datasheet of the TCND5000 I could not understand how it is used. Coul you briefly explain it?

Is your hand inerrupting the reflected IR to activate the thing?

 

[Boncuk]

Hi atferrari,

the hand reflects the IR-transmission beam. Without any obstruction in the radiation pattern nothing will be reflected.

Regards

Hans

 

[Boncuk]

Reflective IR-beam switch

Here is everything of the changed design.

The transformer is slight overkill with 2VA, but it is just 14.5mm (0.57") high and should fit into the wall outlet together with the controller board.

The power supply will be mounted with the components on the bottom and can be wired for 110/220VAC operation.

The controller board sits on top of the power supply board with the components on the component side.

Both boards are connected via female and male connectors (similar to IC sockets).

Boncuk