Simple UV Counterfeit-Money Detector

• When wiring, make sure the red wire from the battery connector is connected to the LED's longer lead. The shorter lead is connected to one lead of the resistor. The resistor's other lead is connected to the battery connector's black wire.
• Hint: The flat spot on the LED is next to the LED's shorter lead.

While I do recommend soldering the connections before taping them, it is possible to merely twist them together and then squeeze the wires with a pair of long-nosed pliers.

The circuit is complete.

Since the circuit will be attached to the battery, electrical tape should be used to insulate the battery before attaching the circuit.

Follow the photo and use the electrical tape to attach the circuit to the insulated battery.

The detector is turned on and off by moving the snap connector back and forth.

• The LED used here produces long-wave ultraviolet light and some visible purple light. Its peak wavelength is 395 nm. Nearly all commercial white paper glows when UV light hits it. However, the special paper used to print US paper money does not. This fact is helpful when making a determination if the money is counterfeit.
• Take a good look at the photo. At the top is a genuine $50 US bill and below it is a $1 bill. Both bills are lying on a sheet of regular copy paper. Notice the difference between the papers.

• In addition to checking the paper to make sure it is genuine, the UV Counterfeit Money Detector also detects the UV strip that is inserted in $5 to $100 US bills. Look at this photo taken of a $50 bill with the LED shining from the back. The strip glows yellow. This is more assurance that the bill is genuine.
• In $50 bills the strip should show up yellow when viewed from behind with the UV LED, in $20 bills it should show up light green, in $10 bills orange and in $5 bills it should be greenish.