I have a cabinet where all my various chargers live -- cell phones, cameras, shaver, cordless drill, Karma, etc.

I would like to install a small light in the closet that will turn on automatically any time the closet door is open. For that, I'll need a small light (could be 120V or maybe a low voltage LED lamp) that can be easily mounted to a wall of the cabinet; and a push-button SPST momentary contact switch that is normally open but closes when the button is released.

This switch is not so easily found, they all seem to be normally open, and close only when the button is pressed.

Can someone point me towards what I am looking for?

tanstaafl.

I use these for controlling LED lighting strips in closets and cabinets.

Unlike traditional magnetic switches commonly used with alarm systems (those open the circuit when the magnet moves away), the SPDT (Single Pole, Double Throw) magnetic switches can be connected to close the circuit when the magnet moves away.

I mount the magnet portion to the door near the top edge, typically closer to the hinge side than the latch side. The switch portion is attached to the door frame, as close as I can position so there are just a few mm gap.

When the door is opened only slightly the gap is still close enough that the switch does not activate. Open the door more fully and the light turns on.

Another gotcha is that a typical alarm system magnetic 'reed contact' is only rated for very low power, typically a few milliamperes at low voltages. To directly control LED lighting strips requires a much higher current capacity.

The Amseco AMS-38BWH magnetic switches are rated for 3 amps at 300 volts, but I have only used them with 12 volt lighting.


Amseco Surface Mount Magnetic Contact Form C White

There are specialized electrical switches that mount into the door jamb or against the closed door. These work similar to the light switch in a refrigerator. Since moving on to LED strip lighting and magnetic switches I have not installed a mechanical door lighting switch in years.

They are still available, I suppose.

Regarding the light source, there has been an explosion in LED lighting. Not only economical cost but they exist in a huge variety of forms. The type I find myself using most often is the LED strip light. A flexible but sturdy tape with LED emitters mounted every so many mm apart, these strips can be cut to the desired lengths and the backing is self adhesive. Very easy to install.

If you want to enclose the LED strip for appearances, extruded aluminum sections are available for mostest cost. Being aluminum they can be cut using hand tools or even a carefully wielded shop saw. I favor the angled profile with white diffuser cover (style 007 in the link).

LED strips are designated based on the type of LED chip used and the density, number of LED per foot or per meter. I find the 5630 (each LED chip is 5.6 X 3.0 mm) type to provide useful brightness. The strips I buy consume 4.5 watts per foot, 300 LED per 5 meter spool.

The most common LED strips run on 12 volt DC power. The power supply is a typical wall wart style or laptop style power brick, depending on how much power is required to run all the lights.

There are dimmers available, including remote control dimmers.

In my view LED strip lighting has superseded fluorescent tube lighting, CFL spiral lamps, halogen pot lamps and pucks. Especially where space is constrained or heat is an issue, such as an enclosed cabinet.

I've been looking at LED light strips recently myself. They're great for this kind of situation. Some of them can be a little dim for task lighting, but still pretty good. They're all over Amazon.

The annoyance for me is that most of them can't be dimmed using my home automation system. I have to use an on/off appliance module in my ZWave system, because while the LEDs can be dimmed, it usually has to be done using transformers. It looks like there's one or two ZWave transformers starting to hit the market, though, so I'm getting more intrigued.

When shopping for LED lighting strips, first figure out how much light (lumens) you need (per foot), and which LED chip type can provide that amount of light (per foot).

Don't look for the cheapest, look for the LED type and brightness first, and the number of LED per foot (or meter). The older, smaller LED chips such as 3528 tend to cost less but put out a lot less light per chip.

Then look at the color temperature and CRI index (if that info is available). This determines the quality of the light. I prefer the 'warm' LED with color temperature around 2700K to 3300K. Others may prefer the 'whiter/colder' 5500K. 6500K to me is getting way too harsh/purple/blue tinged.

All LED dimming is done at the 12 volt DC level, using PWM power slicing to control the brightness. I am unaware of a 'low voltage transformer' for LED strip lighting that can be 'dimmed' from an AC 120 volt wall switch dimmer or equivalent. Of course, none of these 12 volt power modules are actual magnetic transformers. Sometimes called 'electronic transformers', which to me is just a confusing terminology.

Edit: Hmmm, maybe this would be useful for your remote control lighting system? Specs and description are rather thin on what it actually does.

Or this from Armacost.

I'm with you on the color temperature. I like the 2700K range, and usually go with the "soft white" Cree bulbs for my lamps.

This topic got me looking into LED lighting again and whether I could integrate it with my HA system. Looks like I'm in luck! There's this one device that fits the bill perfectly. It's capable of controlling either one RGBW strip or up to four separate white LED strips (what I'd do - I don't want color). It also has support for up to four analog 0-10V inputs for things like light/pressure sensors. I'm going to use that for a pantry door to do something just like you're looking for, Doug.


From what I've seen, there are dimmable strips that operate at 24V and are very bright.

Any old door light switch from a car should do the job. You can get cheap ones on Amazon.

There are 24 volt LED strips, they seem to be less popular and mostly used where extreme brightness is required, or perhaps very long runs of lighting. I have not looked at how they compare cost wise, in terms of lumens per dollar, per foot.

I find that most times the lighting I install uses strip lengths much shorter than the 5 meter length of one 12 volt LED tape spool. Running thin low voltage wiring between segments and back to the power source/controller, even when daisy chaining segments it rarely gets anywhere near 5 meters total LED length in any single combined run.

When using 24 volt LED strips the power supply must also match that 24 volts, as must the controller.

I considered those, but if I decided to use a simple incandescent light fixture I was concerned about running 120V through a switch designed for 12V. Of course, I could always use an automotive 12V bulb powered by a wall wart...

tanstaafl.

It's not what you're asking for, but I have these in my two hall closets. They generally work well. They always come on when I open the door. They usually stay on if I'm standing in front of the closet for a while.

I use something similar for my bathroom cabinets and it always works for me too. Certainly much simpler.

I have used motion sensors for lighting in closets. One annoyance was if the door was left open the light would cycle on each time someone moved near or walked past the opening.

Always multiple ways to solve a problem.

Perfect!

I have placed the order with Amazon. Thank you!

tanstaafl.

Edit: How does the motion sensor work, i.e., sonar, radar, visual, etc? The closet door is a mirror, can I safely assume that the mirror will prove to be opaque to the motion sensor?

db

They're passive IR (PIR) like conventional alarm sensors and you see in the corners of rooms and motion activated lights.

With those, I imagine the motion sensor circuitry has to be drawing a small amount of power almost continuously? So a bit of a drain on the batteries perhaps.

There are hinge-mount battery powered LED fixtures for this purpose which draw no power at all when the cupboard door is closed. Lee Valley Tools sells them, and I imagine they might also be found elsewhere.

-ml

Also, how long will batteries last, in your experience? Because, if it wasn't for that and what Mark mentioned, they are tempting.

I actually ordered this one since the one that Rob linked to had nearly 20% unfavorable reviews on Amazon, with a common thread of spotty quality control (units DOA or dying within weeks). I actually have one of the ones I ordered that my wife bought in California that I installed on a stairwell last week, but was so focused on the idea of a door-activated switch that it never occurred to me that the logical solution was already at hand. The one I have and installed seems to be pretty well made, and it does work well. I haven't had it installed long enough to get an idea of battery life, but I'm hoping for several months at least in the charging closet, where the door might be opened only two or three times a week. If it becomes a problem I'll get some rechargeable batteries for it.

tanstaafl.

Looks kinda large for mounting inside a cabinet.

That said, 4xAA batteries may last longer (perhaps) than 4xAAA batteries.

Not to worry, lots of room. The cabinet holds a 6' tall stepladder, my Dyson vacuum cleaner, and a couple of shelves for the charging stuff. I'll mount the light on the ceiling of the cabinet near the door, pointing down and back.

Of course. All else being equal (i.e., Duracell Alkaline), battery capacity is directly proportional to battery volume. Each AA battery has 2.16 times the volume of a AAA battery, so I would reasonably expect something over double the life compared to the same light using AAAs.

If battery life becomes a problem, I'll just find an old six-volt wall wart, cut the connector plug off the wires and connect them directly to the battery terminals of the light.

Just idle curiosity here, if I used a 12V wall wart, would the LEDs shine more brightly, and would it then fry the LEDs?

tanstaafl.

LED chips are designed to run efficiently at a specific (sometimes fairly narrow) range of current, and have a specific upper maximum current that the LED can handle without excessive internal chip heating. I assume most LED lights run their LED chips at or near the maximum current for peak brightness without excessive heat losses.

How the maximum current is controlled varies with the lamp design. On the 12 volt LED strips there are segments with each segment having three LED connected together in series with a small resistor. The resistor provides current limiting when the strip is powered by 12 volts.

A little more than 12 volts will increase the current through the LEDs and increase the brightness. A lot more voltage applied to the strip runs the very real risk of cooking the LEDs and/or burning up the resistors.

On some small battery powered LED lights the batteries are directly connected to the LED chips with just a switch. The only current limiting is the internal resistance within the battery and the battery output voltage being a close match to the voltage needed to run the bare LED. Raising the feed voltage could easily overdrive the LED.

Some LED lights have actual electronics to control the power delivery to the LED chip(s). These lights tend to be higher priced and high performance LED gear, such as high output LED flashlights.

In addition to what K447 said, you could measure the current that the LEDs use on a fresh set of batteries and then in order to use a 12V adapter, calculate what value resistance to stick in series.
R=voltage/current. Assuming the LEDs draw 40mA and you want to drop 6V (12-6) R=6/0.04= 150Ohm.
Power dropped over the resistor would be P=UxI=6*0,04=0,24W.
The most commonly available resistor type is 1/4W so it would technically do, but it would be running hot, close to its limit. Better to use two or thee resistors in series or parallel to spread the load across them. Maybe 3 51 Ohm resistors in series, or 3 470 Ohm in parallel. Don't bunch them up, give them some distance between them and they should run comfortably.

Another way to drop the voltage would be to stick a number of diodes (maybe 1N4001 ones) in series, each dropping typically around 0.6-0.7V depending on the current. Maybe get a 10-pack, stick them in all in series and check the result. If too dim, remove a diode and check again. Repeat if necessary.
That's what I found inside a cig.lighter adapter for a portable (4xAA) CD player a loong time ago... Crude but worked despite the varying supply voltage of the car (about 12-14.4V) since the player was designed to accept quite a bit of variation in voltage from the batteries it normally ran off.
Or an actual voltage regulator like a 7806 or a LM317 (with a couple resistors to set its voltage.

Unless the lights have some active electronics to regulate the current, the brightness will vary some as the batteries drain (I got a few strings of LEDs for Xmas decorations that run of 3xAA, so nominally 4.5V) But they also work just fine off a 18650 LiIon rechargeable that fully charged is 4.2 and for most of the run is about 3.7V Once I notice pretty much any dimming it means the battery is starting to drop down the tail of the curve and it's time to recharge/switch the battery. Plain AAs I'd run much further down as they're disposable, but LiIon rechargeables don't like being discharged too deep.

If you don't have a 6V adapter and don't want to play with any of the above, you might well find that the light runs at an acceptable level off a 5V adapter, which these days are extremely common and easy to find.

A bit late to the party perhaps, but I would just like to point out Ikea also has a product line specifically for this, the Omlopp series.

I do often forget that IKEA has products and often alternative solutions to common problems.

Of course, they insist on doing everything in the "IKEA" manner, so the power supply is sold separately from the LED lamp units. Actual electrical specs are rather thin

Surprising to me, the power supply notes "To be completed with ANSLUTA power supply cord, sold separately."

Selling the bits separately sounds like a good thing to me. The light fitting and the cable will probably last a lifetime, the power supply will likely need replacing at some point.

Also, the power supply can power multiple light fittings, so again selling them separately make sense.

Link: Wireless Hinge LED