LED Ring Light for Microscopes and Loupes

Most microscopes, eye loupes, and optical comparators do not have the ability to provide lighting for the top surfaces of the specimen being viewed.  If you want to examine a printed circuit board, you would have to use either ambient light or a hand held flashlight.  This instructable will show you an easy way to light the top surface of your specimen.  Most parts can be found in your junk box, but even if you bought all new parts, the cost would be less than $20  Interested?  Lets get started!

Step 1: Materials You Will Need

You will need the following items:

1. A wall wart or wall transformer of about 6 VDC or more and rated at 50 MA or more.
2. A clothes pin or similar clamping device
3. Two or more white LEDs and several resistors of less than 500 ohms.
4. A two inch square of thin plywood, plastic, metal or other stiff but workable material.
5. Some solid or stranded wire of about 20 to 24 AWG 
6. tape or shrink tubing to cover the wire joints.
7. A soldering iron and solder to solder the wires to the LEDs and wall wart.
8. Tools to cut and shape the plywood, wires, etc.
9. Drill bits or dremel cutter to drill holes for LEDs

There's nothing difficult or fancy here so feel free to improvise.

Step 2: Things to Note Before You Start

The pictures show only my way of doing this.  Feel free to improvise.  You may want to add more or less LEDs or you may have an optical  device with larger or smaller housings.  Your dimensions and electrical requirements may be different from mine, so I have provided no drawings or schematics.  It would be wise to layout your LEDs and wall wart before starting and check them for proper brightness or any overheating.  Figure on about a 3 volt drop and 20 MA of current per LED.  Do not connect the LEDs without proper current limiting resistors.  Start with high values for the resistors.  If you are not familiar with wiring LEDs, get some help or search the internet.

Step 3: Building the Mounting Ring to Hold the LEDs

Measure the outside diameter of the device you are building the ring for.  This will be the inside diameter of your mounting ring.  Make the outside diameter of your mounting ring about 1.5 inches bigger.  If you do not have the exact size drill bit for the Inside diameter, then use a smaller diameter bit and sand or file the hole until it fits snugly on your optical device.  Do not cut the ring in half until it is glued to the clothes pin.  It you are using plywood and it cracks, try laminating two pieces with the grain oriented 90 degrees to each other.  

Step 4: Drilling the Holes for the LEDs

After you have determined how many LEDs you want to use, lay out the drilling pattern on the mounting ring.  The holes can be drilled at perpendicular to the ring.  As an option, you can angle the LEDs toward the ring center so that they focus about an inch away from the ring.  You can use white craft glue or epoxy, or shoe goo to glue the LEDs in place.  Do not use CA or crazy glue because this will fog up the LEDs.  Wait until the LEDs are secure before gluing the ring to the clothes pin.

Step 5: Attaching the Ring to the Clothes Pin

Notch out a clothes pin to accept your mounting ring as shown in the pictures.  Use a glue appropriate for the materials that you selected.  After the glue has set, cut the ring in half.  Check for proper clamping action before wiring up the LEDs permanently.  Wire up the LEDs and the wall wart . (You did check out your circuit before hand didn't you?)  You are now done - enjoy!

Step 6: Some Options...

1. You could use a rechargeable battery pack for field operations.
2. You could add a variable resistor to adjust  LED brightness.
3. Add a camera to record your images