Little Red Night Light Is Just Right

Don’t you hate getting up in the middle of the night to use the bathroom? The worst part is not being able to see what you’re doing, but if you turn on a light, you’ll lose your night vision. Nightlights are supposed to be the best solution, but are usually too bright for 3 AM excursions and can end up leaking light into the bedroom. What the bathroom needs is a purpose-built nightlight that uses red light so you don’t lose your night vision.

This simple, wall-mounted night light is just the thing. All it takes is two AA batteries, a resistor, a red LED, and an SPST push button. [Vchaney] even made their own battery contacts. The genius part of this build is in the adjustable LED, which is fitted into a ball that moves around in a socket so you can aim it wherever you need to see. All the files are available if you want to print one for yourself.

Those who sit might prefer to shine the light on the toilet paper roll. Here’s a smart roll holder that doubles as a night light, albeit a terribly bright one.

35 thoughts on “Little Red Night Light Is Just Right

  1. Before my balance went away and I found I needed more light to walk I used a Streamlight Siege Lantern that uses 3AA batteries. The link is to a test I did of two versions of the Siege Lantern some years ago. I now use the 3D version with rechargeable batteries (don’t want to bother getting a new lamp for the far side of the bed).

    For the 3AA version there is also a very low level red light that runs for 190 hours and seems to be popular with amateur astronomers as the light is low enough to not disturb their night vision at all.

  2. Contrary to conventional wisdom, I’ve found that blue LEDs make the best night lights. They only need to be extremely dim to work effectively and it is the rods, not the cones in your eyes that are super sensitive to blue light, which is much more energetic than red light. Done right, blue LED night lighting is similar to moonlight. The forward voltage drop of blue LEDs is higher than red ones, so a typical homebrew battery operated night light uses a 9V battery or a lithium cell instead of two alkaline cells in series.

      1. You need about 3.2 volts for the LED plus the forward loss of your current regulator (1.25 Volts is typical for an LM317) so if you’re using basic linear regulation you need a minimum of 4.5 Volts. An AA/AAA cell goes down to about 0.9 Volts per cell when absolutely empty, so the minimum number of cells you need is 5.

        Of course when you’re running the light so low, you only need a very small amount of current, so the LED will run at around 2 Volts, which means about 3.3 Volts minimum, or 4x AA/AAA cells.

        If you want to go down to microamps, then you don’t necessarily need a regulator at all because the diode will work like a linear resistor below 1.5 Volts. Put a few cells in parallel and the blue LED will glow dimly for a year. (single AA = 2,500 mAh, or 100 days at 1 mA)

        1. An LM317 is also a very inefficient current regulator and it does require 1,25V + 2 BE voltages of the darlington output stage: 2,5V to 3V. Yes, if you use this inefficient solution, a 9V block could be used.
          An efficient current regulator consists of a shunt (less than 100mV drop, in the source connection of an NMOS device and a Rail-to-rail OPV. The load (LED) is connected from BAT+ to the drain pin. You have not much more drop out voltage than the shunt voltage.
          The OPV does not really need to be R2R, the good old LM358 or LM324 is sufficient.

    1. But if you look directly into the light at any time, you immediately get a blind spot that lasts up to 30 minutes where the rhodopsin has bleached in the rods. You also can’t see by foveal vision under blue light, because there’s less rods there. The center of your field of view becomes effectively blind, and you need to look 15-20 degrees off to the side for example to read text.

      Dim blue light is good enough to navigate by, and see approaching predators in your peripheral vision, but if you need to be able to read signs or instructions, or just look directly at things to make out what they are, then you need your foveal vision. For foveal vision, the most effective color is green, but it requires enough intensity that it kills your night vision right away, so red is used instead. Sodium lamp orange is also a reasonable compromise.

      1. Amber light seems like it would be a pretty good compromise in non-critical environments where you don’t need the absolute maximum night vision.

        I wonder why cool and neutral white street lights are allowed to exist for any reason?

        Street lights maybe shouldn’t exist at all without some kind of modeling to be really sure they reduce accidents in that specific spot, but spewing ugly bluish light is extra bad.

        1. Because it’s actually cheaper and more efficient to produce the medium wavelengths of green and yellow by secondary emission out of a phosphorescent dye than by direct emission out of a LED, especially since you want them to have a somewhat broader spectrum than the single line of a low pressure sodium lamp, which is also characteristic of the pure LED device. This is why streetlights were changed over to high pressure sodium lamps before they became LEDs.

          Using a phosphor implies you’re using either UV or blue light to excite the dye. The UV would be a waste, so they use blue to make a pseudo-white LED. It has great apparent brightness, but it makes you effectively color- and night-blind.

          The irony is that HPS is still just as efficient between 100-150 lm/W so there’s no real argument on that front. The LED salesmen just have their pitch about “25 year service life” which usually isn’t true at all because the electronics are more complicated and less robust against transients and moisture.

          Plus, since the individual LED units are lower in power to keep them from overheating, they are installed lower to the ground and the light is spread more sideways, which makes them shine right into your eye. It’s just one terrible design compromise after another.

    2. The advantage of red light is precisely that rods are completely insensitive to it, which is why night vision doesn’t suffer even after exposure to rather bright light. As long as you don’t really have to worry about battery life, it’s a huge plus.

      1. well, people who go to sea and need ot read or use instruments at night have been using red night lights for a *long* time. I’ve tried a very dim blue light in the nav station – because it was all I had at the time – and you lose much of your night vision very quickly, and can’t read books at all.

    3. I thought your biological clock reacts to blue light. And so imo using a blue light is the wrong idea because it says to your brain: “Hey there, it’s day, wake up!!” That’s why the nightlight mode on laptops, phones or tablets removes the blue from the picture, to not mislead your brain into thinking that it is the middle of the day.

  3. Regular night lights give off too much light. The solution is a neon guide light. Uses .3 watts, plug it in and forget about it, it will last forever. Great for the kitchen and the hallway. I got mine from Amazon.

  4. I painted small lines and dots on walls, and in particular corners, using glow in the dark paint. It is just enough to orient yourself and then your memory is able to fill in the details. Also a targeting crosshair on the toilet bowl. :-)

  5. Every darn electrical device I own has some sort of glowing LED. My problem at night is not finding my way to the bathroom, but figuring out what to put over these beacons so I can sleep.

      1. That’s the truth! When they finally figured out how to make blue LEDs it seems like EVERYONE started putting them on things. My “favorite” was a cig. lighter plug powered device I had in my car for a while. It had this insanely bright blue LED. At night it would completely ruin your night vision, so I wrapped the whole thing in electrical tape.

  6. I built one into a battery charger and bring it on trips. Those strange motel rooms with completely dark bathrooms can be dangerous. I just plug it in and 1 ma goes into a white LED and provides plenty of light. I used a plug-in AA charger with a translucent cover. No batteries required,

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