1. Home
  2. Electronics Design
  3. Light activated switch

Light activated switch

Hi All,

I have just added a 15W fluro under a shelf in the bathroom. It has it's own switch but when the light is on the glare is so great it is hard to visually find the switch. I know where it is but others may struggle with it and probably just leave it on. I know the wife will!! {grin}

I'd like a switch that detects the main bathroom lights coming on and that then turns on the new fluro. Also it must turn the fluro off when the main lights go off.

I found this and it looks simple enough, but it works the wrong way round. I know I could wire the relay to work the way I want but then the circuit is always active when there is no light. Not drawing a lot of current, I know, but...

formatting link

Also it requires a 9v power supply and I was hoping someone could come up with a simple design that used 110-mains voltage as I hope to install it all inside the fluro case.

I can assemble parts onto a board but I am hopeless at design, so a schematic is essential for me.

Thanks

Dave

Reply to
Dave, I can't do that
Loading thread data ...

On a sunny day (Sat, 29 Jan 2011 10:58:45 -0800 (PST)) it happened "Dave, I can't do that" wrote in :

You can get one of those cheap motion detectors, and control all the bathroom lights with it. No one there, after say 1 minute (adjustable) it will switch off. If somebody is there, it will go on immediately.

Reply to
Jan Panteltje

Yes, but don't try to read in there.

I you are reading on the pot and not moving, the lights will go out on you.

More fun with technology.

hamilton

Reply to
hamilton

What's needed here is a propper motion detector....

Reply to
TTman

LOL, how much do you move when your reading !

:-)

Reply to
hamilton

formatting link

I guess it's natural that most light-sensitive switches for switching a light on are designed to turn on when it's dark. Technically, it shouldn't be difficult to design one that does the opposite. More than one possible configuration come to mind, but right now I don't have time to work out the details with all component values. There are a couple of things you should be aware of: 1) A simple and compact design that uses mains voltage directly will probably have to have all parts of the circuit live. 2) The light sensor will have to distinguish between the main lighting and the added fluoro. Otherwise, it will be kept on by its own light. Shielding and careful orientation will be needed.

Reply to
Pimpom

And once in the bathtub, the light flips out again......

Reply to
Sjouke Burry

The one I have in the garage can be set to as high as 15 minutes, but the slightest motion resets it. Just wave your arm if it goes dark ;-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed
Reply to
Jim Thompson

If someone is too lazy to turn on the lightswitch, they would be too lazy to wave their arm.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.
Reply to
Michael A. Terrell

can you wire the new fluoro in parallel with the existing lamp?

Arranging a light detector to not see the light from the nes fluoro may be tricky.

--- news://freenews.netfront.net/ - complaints: snipped-for-privacy@netfront.net ---

Reply to
Jasen Betts

Thanks everyone,

I should have mentioned I had a battery powered light with motion sensor but it drove the wife nuts. (some may say a short trip :) ) The light is above her makeup tools and potions so it only saw motion from her midriff. When it went out and started up again, it was just an orange glow for about 10 seconds. before getting the correct daylight- color. Yeah, I know ten seconds and daylight, but hey I like a quiet life and the motion sensor didn't cut it.

I had not thought about the light affecting the sensor. I need to see if I can run a remote wire for the sensor. Actually just thinking about that I could run the sensor and wire up through the top of the shelf as the light is underneath and very little light is likely to be reflected around and over the shelf. Especially if I can adjust the sensitivity.

Connecting it to the main lights would be a major job with very long drills, fish-tape, crawling around the ceiling space and more patience than I possess.

@pimpom I am not overly worried about the circuit always being live. When I mentioned that, I was thinking that the circuit I linked to I would just have the relay coil wired in reverse but it would always be energized when the light was off. I figured that would not be good.

Dave

Reply to
Dave, I can't do that

Running the sensor wire around was one of the reasons why I mentioned the circuit being live. See below.

I thought as much, which is why I didn't suggest that option although it crossed my mind.

What meant when I mentioned the circuit's being live was that it could be dangerous if there was any possibility of touching any part of the circuit, such as in the sensor wiring. This will be the case if it's powered directly from the mains without an isolating device like a transformer. A transformer or wall wart will add bulk which you seem to want to avoid. A switched-mode power supply will add complexity and cost. Using a 9V battery will solve these problems if you don't mind having to change it from time to time.

As for the working principle, exchanging the positions of the sensor diode and the base resistor will have the effect you want. You can use an LDR instead of the photodiode.

Reply to
Pimpom

OK, thanks, the fluro has a rather large plastic case with quite a lot of room inside. They have made a large open box-section to coil and hide unused cord so fitting it all inside should be fine. I may even be able to fit a small wall-wart inside the case.

Dave

Reply to
Dave, I can't do that

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.