UV Nightlight / Bulletin Board





Introduction: UV Nightlight / Bulletin Board

About: After a career in industrial electronics I went back to college and now do DNA research.


This simple and practical ultraviolet (UV) nightlight project will illuminate your home with a beautiful soft blue/green glow at night. It is also bright enough to use as a small message board during the day to remind you of those important appointments.

You can write or draw on it using a standard yellow highlighter which glows a green color. I bought a pack of various color highlighters only to find out that yellow was the only color that would glow under UV. You may want to try your luck and see if you can find any other markers that work. If you do, please post a comment and share it with the rest of us.


S A F E T Y . N O T E :

The term "Ultraviolet", is misleading when used to describe LEDs. UV LEDs actually emit "near ultraviolet" light (400nm). This narrow wavelength falls within the same, much broader, band as regular fluorescent black lights. This means that UV LEDs are completely safe and will NOT damage your eyes or give you skin cancer - no matter what you have heard or read elsewhere on the internet.






You may already have some of these parts in your junk box. If you do then your project cost will decrease.

(1) 5VDC/300mA Unregulated Power Supply (Wall Wart)
PWR1258 @ $1.49 each from BG Micro

(1) 2.1mm 2.1mm Barrel Connector Plug
#PWR1255 @ $.06 each from BG Micro

(1) 2.1mm Panel Mount Power Jack
#PWR1145 @ $.99 each from BG Micro

(2) Ultraviolet (UV) LEDs
#LED1078 @ $1.49 each from BG Micro

(1) 3mm Sintra Expanded PVC Sheet (8" X 12")
$3.25 each from Solarbotics

(1) Piece of Plexiglas (mine is about 80mm X 100mm)
Available at your local building supply

(2) 150 ohm 1/4 watt resistors

If you need to purchase these items then I can recommend these sources:

BG Micro
web site
I am only a hobbyist and I don't spend a lot of money on projects, but the people at BG Micro have always treated me like I was their most important corporate customer. That kind of service is nearly impossible to find these days. Add that to their great selection and low prices and you have a winning combination.

web site
Solarbotics is a great company with great products, but they are located in Canada. Because of this, you will need to allow a couple of extra days for shipping. You might be able to find a US source for small pieces of Sintra (less than several square feet in size) but I could not. If you do find a US source, please share it with us by posting a comment.




You have limitless options when it comes to a case. I used 3mm black Sintra for mine (see note below). You could use an Altoids box, a small plastic, metal, or wooden project box, or even a cardboard box. You may even want to use an old picture frame. You could put a photograph in the frame or just a sheet of black construction paper to give it a cool high contrast look. You can also use a plastic CD/DVD case instead of the plexiglas, but in my opinion the results you get with glass or CD/DVD cases is not quite as good as with Plexiglas. Plexiglas has special light guide properties that really make the fluorescent ink glow brightly. You can always wire up the LEDs and try different materials to see what suits you best.

If you use a case similar to the one I made you will need to cut a slot in it for the Plexiglas like shown below. The Plexiglas needs to at least be flush with the inside of your case. It won't hurt if it extends inside the case a little so long as you leave room inside for the rest of the parts.

If you decide to use an old picture frame or some there material you are on your own at to how to mount the LEDs so they will shine onto the edge of whatever material you use. If you come up with something that works I would love to see a picture of it.

NOTES: Sintra is sort of like foam core board, but it is made of PVC and is much stronger. It is pretty easy to cut to whatever size you want. Just score it a few times with a utility knife and then snap it in two. After cutting, sand the edges smooth with sand paper or an emery board normally used for fingernails. You can glue Sintra together using super glue.
It is available in various thicknesses and colors. You can buy it from several sources but Solarbotics is the only source I have found that sells it in smaller sheets (8 inches by 12 inches). If you decide to buy some from Solarbotics, I suggest that you buy several sheets in various thicknesses and colors because once you use this stuff you are going to find a thousand uses for it. It is great for all sorts of projects - especially robotics. Sintra adds a certain professional look to your projects that is hard to achieve with any other product.




I used a 4.5 volt wall wart transformer to power my nightlight. You can buy a power supply or maybe you have an old charger that went to a cell phone that died long ago. Whatever power supply you use, make sure the output is direct current (DC) and not alternating current (AC). The output voltage is not really too critical so long as it is in the 3 to 9 volt range. You can always adjust the resistors for whatever voltage you have. See my note below to figure out what value of resistor you need to use.

I used a plug and jack with my power supply, but you could just solder your power wires directly to the LEDs and resistors. This thing uses very little electricity so a switch isn't necessary.

NOTE: To determine the resistor value you will need you need to know the power supply voltage. It should be clearly marked on the power supply. As an example, suppose your power supply puts out 6.0 volts. Just divide 6 by 0.03 (30mA) which is the maximum current the LEDs can take. This value should be the same for any UV LEDs you buy. Doing the math gives you 200. Go to Radio Shack or your junk box and find a resistor that is 200 ohms or greater. I won't matter if it is a bit larger than the number you came up with. In this case a 220 ohm resistor will work fine. Just don't use a resistor with a value less than what you calculated (in this case 200). If you do go lower, your project may still work, but the LEDs will slowly loose their UV qualities and your nightlight won't glow as brightly.




I have included a JPG graphic file and a metafile (UV Nightlight.emf) of the schematic below. The LEDs (*) need to be soldered to the resistors and then these components need to be soldered to the power supply. Allow enough extra wire so you will be able to move the LEDs around and aim them at the edge of the Plexiglas after soldering.

When you are finished you can squirt a little hot glue on and around the LEDs and resistors to hold everything in place and make sure nothing shorts out. Be careful not to fill your power jack up with glue or the connector may not go into it.

(*) LEDs are polarized components which mean they can be installed the wrong way. They need to be soldered into the circuit correctly of they will not work. There are several ways to tell which wire coming out of the LED is which. The easiest way for me to tell the difference is to look at and feel the round base of the LED. There is always a little flat area on the side of the base next to the lead that goes to the negative side of the power supply. Just feel around the base, find the flat side, and make sure that side goes to your negative wire.

(**) The power leads coming from the wall wart are also polarized which means, just like the LEDs, they can be hooked up the wrong way. You will need to check out the label on your wall wart to find out how which wire is + and which is -. Once you have the resistors soldered to the LEDs you can touch them to the power wires or power jack terminals to see if they light up. If they don't, simply reverse the leads. Once you get the LEDs to light up, solder them to the jack terminals or power leads.


Step 5: POWER IT UP!


Turn on the power and hope you don't see or smell smoke.

Write or draw on the plastic or glass with a yellow highlighter. The more you of the highlighter ink you put on it the brighter it will be at night. I guess you could say this project has an adjustable brightness control option.




I hope you enjoy building and using this fun and practical project as much as I have. Hopefully you will post an instructable of your design so we can see what you came up with.






Thank you for taking the time to view my project.

I hope it will inspire you with new ideas of your own.

As Thomas Edison said,

"To invent you need a good imagination and a pile of junk".

Thanks Again,





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I was pondering the idea of using a black sheet of paper behind the Plexiglas, before seeing that I could actually purchase Plexiglas with a slight tint to it. The idea is to allow better contrast. Do you think the tinted Plexiglas will prevent the effectiveness of the LED's?

1 reply

I have no idea what effect plexiglass would have. A paper our plastic backing should add some cool effects. If you try the tinted plexiglass please let me know how it works. Best building!

For the LED's, would something like this work?


It's a string of 20 purple LED's that are powered by 3-AAA batteries, and costs $15. According to the description, they are "almost UV".

Here's what I came up with just in case you'd like to see your idea being used : I gutted an old X-Box 360 SMPS I had laying around to use as the base/stand. I used 3 U.V. L.E.D.'s just to be sure I would get the desired effect. I also used a simple power plug I installed on the back side of the base and a 5.2vDC 320mA supply. And the best markers I found were Expo NEON Dry Erase Markers. Here are a few photos of my finished product :

6 replies

I forgot to add the pics ! Here they are :



I love what you came up with! This is so awesome! I like your game console base idea. Brilliant! I especially like the way you drilled holes for the LEDs instead of cutting a slot for the plexiglass. That is much simpler than the way I did it. Cutting that slot was a real pain in the rear. Also thanks for the heads up on the dry erase markers. I never took the time to experiment with anything other than the yellow highlighter. I like your modifications so much I think I am going to make another one and give it to my daughter. Thank you so much for sharing the pictures with me. I wish you the best on learning more about electronics.

Thanks again,


Thanks a lot ! Another thing is the plexi glass - There were two two types at the store - The regular and the one that is supposed to hold up in outdoor conditions. I bought them both thinking the outdoor version would be better because it was just a tad bit thicker, but NOO - The regular worked far better to "hold" the near U.V. light.


Doesn't the outdoor stuff have a UV block?
Maybe that's why it is not as good - by design.

I didn't even think of that. HA ! I guess sometimes the most obvious things are the easiest to miss ! That has gotta be why it sucked. Good thinking !

And there actually is a slot for the glass .... It sits down in there right on the top of the L.E.D.'s. ... It's only about 3mm in however and I used 2 part epoxy glue to stabilize it. I had to cut little metal plates to hold the L.E.D.'s. And hopefully I'll learn quickly ... I have been in fact. My dad's degree is in electronics - He's an Electrical Engineer - He uses it every day. So I have a pretty good teacher ! Thanks Again !

Thanks for responding ! I didn't think I'd get an answer ! I researched a bit more and found out ... Another question I've got is why not this : (5.2v-3.3v)/.03mA to find resistors needed ? 5.2v = source, 3.3v = led volt. and you know the mA. I have not been able to find an answer to this ! (Just by me researching on Google) Is there an actual explanation for why you didn't find resistance this way or is it cause this is a bit more simple and user friendly way of doing it ?

3 replies

You cannot determine the resistance needed for the circuit using that method because that does not take into account the voltage drop across the resistor and the LED. Using the values you gave in your example you would come up with a 63 ohm resistor when you would really need a 173 ohm resistor. A 63 ohm resistor would allow over 80 milliamps to flow through the LEDs. That is almost three times their rating. They would fry in no time. I suggest you look up ohm's law. Check your local library for a book on basic electronics. I assure you it will be time well spent.

I guess also if I would have really paid good attention you answered this question in your reply to my question yesterday !! Ha ! Thanks Again !

That's what I came up with using the method you gave - 173. I have read and read and re-read the Ohm's Law wiki page - HA ! I think that's what I'm going to do is go pick up a book because this is all SOOOO interesting !! And THANKS for the explanation and your time !! I really appreciate it.

Because that is where it worked best for me from a purely physical layout perspective. This is a series circuit and the resistor will limit the current no matter which side of the LED it is on. It makes no difference at all.

Also - This is a neat idea - I'm sure you've been told ! I see you've been told ! Even 3 years later ! I'm making one of these for my little sister for her b'day coming up - So thanks for the idea !!

this ones really coooool !!!!!!!

it'd be cool to adapt this to a message board format for a college dorm or something. put this thing up in your room and have the girlfriends leave you secret messages

just out of curiosity, how does this perform in light?