Detecting money can be very useful for allot of people. For instance shop owners, you don't want people to buy stuff from you with fake money.
This money detector disguised as a mouse will look nice behind the counter and is very easy to use.

I got this idea when I found this mouse in some junk box upstairs. Unfortunately this mouse died... about 15 years ago.
Can you believe it, this mouse had a ball inside of it. I used these mouses allot back in the day, and I think some youngster don't even know a mouse like this did exist :)

Anyway, below you'll see a movie and some photos of the end result.
Hope this instructable is useful for you. Or at least fun to watch :)

Note: The photo below and in the movie show blue light coming from the UV LED. I think it has something to do with my camera not being able to capture UV light correctly. The UV light coming from the LED is more of a purple color.

Step 1: Materials & Tools

There aren't too many materials needed to make this. Next to this the materials are pretty cheap. So it doesn't have to cost much to make this.

You need:

- Old mouse (Using a new one would be stupid. But if you feel like using a new one, be my guest)
- 1x UV LED 5mm
- Button cell 3v (I used a CR2032)
- Button cell holder
- Electrical wire
- Tinfoil (sorry, forgot to put this in the photo below).

- Screwdriver
- Glue gun (hot glue)

Once you've got this stuff you can start.
I've got to note that there are some parts in building this where you need to be gently and patient (that's when we're going to use the tinfoil :)

Step 2: Preparing the Mouse

1. Open the mouse with the screwdriver.

This mouse was stuck together with only 1 screw. It's possible that your mouse has more screws and they might be hidden (under some stickers maybe).
Be sure to get all the screws. You don't want to force anything and break the mouse.

2. Inside you'll find everything that's needed for a 'mouse' to work. We don't need anything of the electronics and parts (photo 2). So remove all of that. Again don't force anything cause it might break the casing.

Oh, and don't loose the screw, like I did. Took me about 15min to find it back.

Step 3: Tinfoil Connector

Since it's a mouse it's nice to make the money detector work with clicking a mouse button.
Therefor I choose to use tinfoil. It's really thin and easy to work with (if your gently).

1. First you want to remove the mouse buttons from the upper part of the casing.

2. Cut 2 pieces of tinfoil that will fit nicely on the inside of the mouse button.

These next steps you need to do gently and patiently. You don't want the tinfoil to shred.

3. Gently glue the 2 tinfoil strips on both parts (see photo 1). You need to glue them right on the edge.

Once done with the whole project, these 2 parts will join when clicking the mouse button. This will complete the circuit and make the LED light up.

4. Once the glue is dried up, we need to attach electrical wire.Strip the ends of the electrical wire and wrap it up in the tinfoil. This should be done patiently and very gently. We don't want to shred the glued tinfoil.

5. If you've got the electrical wire attached to the tinfoil, use the glue gun to stick it in that position. This way the electrical wire can't get loose from the tinfoil.

6. Once the glue is dry you can put the mouse buttons back into the upper casing.

When done you should have something like photo 4 below.

Step 4: Attaching LED and Battery

Now it's time to insert the LED and attach the battery.

Before you continue, you need to be sure you make a correct circuit. The LED and battery should be place correctly. So the positive side of the battery should make contact with the positive leg of the LED (the positive leg of the LED is the longer one).

Test this first before you going to attach everything and glue it together.

1. Attach the LED to the electrical wire of the upper part and mount a small electrical wire on the other end of the LED (photo 1).

2. Put the the LED in the hole where normally the mouse cable goes through. I've used a 5mm LED and it fit perfectly.
Glue the LED with the glue gun so it stays in position (photo 2 and 3).

3. Put the 3v battery in the battery holder and attach the 2 electrical wires on the correct sides. Glue them a little to they won't let go (photo 4).

4. Glue the battery holder on the exact same spot as the mouse ball was (battery facing down). This way, when the battery runs out, you can easily change it without opening the whole mouse casing.

Check if everything is glued well together and nothing can let go. If so, you're ready to finish it up.

Step 5: Finishing Up

If you've done everything correctly, you're mouse should now look the same like photo 1 below.

1. Now put the top and bottom part together and put back in the screw.

You're done!

It should now look like photo 2. Now press the mouse button and see if the LED will light up like in photo 3.

On photo 4 and photo 5 you can see why we glued the battery holder the way we did.
Like this you can easily change the battery when needed.

Note: In the photos the UV light shows up blue. I think it's because my camera can't capture the UV light correctly. UV light is much like purple (more purple then blue).

Now go check your bank notes if they're real :)