Posted on Leave a comment

Mk1 / Mk2 Boba Fett Range Finder

This is a self contained rangefinder I designed. No stalk hole is cut in the plastic, so it fits a variety of helmets. Runs on a CR2032 battery and turns on when tilted down.

Kit Overview

The kits consists of the following parts:

  • Circuit Board
  • Main Body
  • Clear Diffuser
  • 2 Phillips Screws


Take the range finder out of storage mode.

The top of the range finder has a small slot. Inside is the storage / power switch. Flip the switch to turn on.

Tip: You can use a toothpick or pen to move the small switch.

Storage Switch

How to Replace / Install Battery

Use a small screwdriver to remove the screws and diffuser.

Insert a CR2032 button cell. Make sure that the + symbol is facing up.

Tilt Circuit

Spin the circuit in your hand to activate the lights.

Installing on your Helmet

Unless you requested otherwise with your order, your range finder will not have a hole to attach your helmet stalk. You will need to cut a hole in the plastic.

Cutting Tool Examples (pick one):

  • Hot knife
  • Solder iron
  • Wood burning tool
  • Drill
  • Dremel

Use the wrench to remove the clear diffuser. Then carefully push on the two LEDs to pop the circuit out of the plastic shell. Try not to bend the tilt sensor’s position.

Tip: You can use the included wrench to push the LEDs through the holes.

Now with the diffuser and circuit removed, you can cut into the plastic without damaging them.

Remember to cut in a well ventilated area.

Adjusting the Tilt Sensor

Mk2 Solid State Sensor

Each circuit is calibrated for ~45 degrees. If you would like a different activation angle, you can adjust using the blue screw wheel.

Remove the circuit from the plastic housing. Then hold the circuit at the desired angle of activation. Rotate the screw wheel so the lights just barely come on. Test a few times by rotating the circuit.

Mk2 Angle Adjustment Screw

Mk1 Mechanical Sensor

You can carefully bend the sensor to adjust the activation angle. Pay attention to the bead inside the sensor to figure out the best angle to activate. 20 – 30 degrees works well.


Range finder doesn’t light up

Replace the battery.

Clean the battery clip. High humidity can cause a white film to appear on the battery clip. Use rubbing alcohol and a qtip to scrub away.

Remove and re-insert the battery several times. The friction cleans the battery contacts.

Flip the storage switch to ON.

If you have a mechanical tilt sensor, check if you can see or hear the ball move. If not, contact for a replacement sensor.

Range finder lights up erratically

You can adjust the angle of the tilt sensor to make it less sensitive. See above for Adjusting the Tilt Sensor info.

Tilt sensors are sensitive vibration and acceleration, so running and other movements will activate the lights the same as tilting.

Range finder is still dim after replacing the battery!

A similar shaped battery was used, but not a 3V Lithium CR2032.

Your new 3V Lithium CR2032 battery is expired. Check the expiration date. Expected shelf life is 5-8+ years.

Battery Notes

Expected Battery Life

It is important that you switch the range finder OFF when not in use.

Sensor TypeBattery Life (Idle)
Lights OFF and Switch ON
Battery Life (Active)
Lights ON and Switch ON
Mk1 Mechanical5 – 8 years2 – 4 days
Mk2 Solid State4 – 6 weeks2 – 4 days

Replacement Battery

You will know it is time to change the battery soon when the white LED is too dim to see. The red LEDs will be next.

Name brand replacement batteries are recommended. In my experience, Duracell’s CR2032 lasts about 10% longer than other brands.

Look for “3V Lithium CR2032” on the package.

Battery Life Analysis

Below you can see what the lights look like at various battery voltages. Use to determine if your battery needs replacement.

Photos show a voltage current test, starting at 3.00V then dropping to simulate a dying battery.

A brand new 3V Lithium CR2032 will measure ~3.2V out of the box, then quickly fall to the 3V operating voltage.
Most name brand CR2032 cells will stay at 3V for the majority of their lifespan.
Eventually, you will see the white light become dimmer and dimmer.
It is time to replace the CR2032 battery.