Our Keurig coffeemaker sits in a dark corner. The water reservoir is charcoal gray. I often rise before the sun comes up. It is difficult to know if there is enough water in the reservoir to brew a cup of coffee. This Instructable will show how I added an LED light that indicates the water level with a glance.*

Tools

Drill
Saw
Screwdriver
Soldering gun
Metal shears
Heat gun

Materials

Wood strip
Screws
Sheet metal
9 volt battery
Battery clip
150 Ohm resistor
LED flashlight
#10 plastic coated wire
Heat shrink tubing
Polyurethane foam

*Newer Keurig machines have gone to a clear water reservoir with a blue LED to illuminate the water level. And, I first considered tapping into the Keurig circuitry to add an LED that would always be "on" when the machine is "on," but I would have had to go into the machine through the bottom and remove everything to get to the circuit boards at the top. I chose a lower tech. path that means adding a battery powered flashlight "on" only momentarily.

Step 1: Rip and Cut Wood

First and Second Photo--Rip a piece of wood 3/4 inch wide and not quite as thick as the mounting screws will be long. I do not know for certain what is inside the Keurig, although I have seen videos on YouTube. I do not want the screws to be too long, nor to have sharp points, lest they puncture a soft water hose or pierce a wire. I ground the points flat. Only enough screw length reaches beyond the wood to attach to the plastic in the Keurig's exterior.

Third Photo--Carefully drill holes for the screws in the outer case of the Keurig next to where the water reservoir mounts. Attach the wood with the screws. I may one day paint the wood black, but no one sees it in normal use.

Step 2: The Flashlight

The pencil thin LED flashlight uses specialized batteries that are expensive and usually must be ordered. Each is 3 volts and the pointed end is the negative terminal. I will be powering the flashlight with a "dead" 9 volt radio battery that is still very close to 9 volts.* I used an app. on my phone that includes an LED calculator for determining the value of the resistor needed to protect the LED from burn out. Because the flashlight uses 6 volts of power, I used that as the forward voltage of the LED, even though that is surely higher than most LEDs. The input voltage is 9 volts. I selected 20 milliamps as a safe current level. The suggested resistance is 150 Ohms. See the second photo.

The third graphic is a diagram of the circuit.

*We use 9 volt batteries in smoke detectors and external keypads for garage doors. We change them every year for safety and dependability. Usually they are not at all near to depleted. They are perfect for this project.

Step 3: Connect With the LED

The photo of the batteries in step 2 shows a very pointed end. I discovered the inside diameter of the flashlight is just a little larger than the plastic insulation on a piece of #10 house electrical wire. I cut and straightened a piece long enough to extend outside the flashlight. I ground a sharp point onto the end of the #10 wire.

Step 4: Mount the Flashlight

The flashlight shines on the countertop behind the water reservoir. I bent some sheet metal about 24 or 26 gauge around the flashlight. The pen clip keeps it from slipping. I drilled the sheet metal and used a screw to attach it to the wood strip. One conductor makes the circuit through the barrel of the flashlight. I slipped one wire between the layers of sheet metal and tightened the screw holding the flashlight mount to the wood.

Step 5: Mount the Battery

I made a sheet metal wrap to hold the battery much like the holder for the flashlight in the previous step and attached it with a screw.

Step 6: The Switch

I had planned to use a momentary contact button switch. But, the #10 wire slides freely inside the flashlight. Initially, I had a little cloth electrical tape around bare #10 wire at its upper end. Sometimes it became stuck and the light stayed on. I replaced it with some heat shrink tubing. I added some polyurethane foam to act like a spring and raise the point of the #10 wire when finger pressure is removed. The circuit is made with a little downward finger pressure. What is shown in the photo is just below the back of the top surface on the Keurig. I reach over the top with one finger and gently press downward. See the second photo. When I remove my finger, the LED light goes out. (The second photo was taken before the cloth tape was removed and the polyurethane foam was added.)

Step 7: With and Without

The first photo shows how difficult it can be to see the water level, even when there is some daylight. The second photo shows how the light illuminates the water level line.