Building a $10 Laser Power Meter from Scratch

A DIY project was undertaken to create a laser power meter, which is a device used to measure the power of a laser beam. The project aimed to replicate the functionality of a commercial laser power meter at a significantly lower cost.

The first step involved assembling the necessary components, including an Arduino Nano, push buttons, USB type-C charger, ADS1115 ADC module, buzzer, and OLED screen. These components were soldered onto a custom-designed PCB (Printed Circuit Board) to form the core of the device.

Next, a Peltier cell was painted with a fine coat of black paint and allowed to dry. This cell would be used as the heat absorption element in the laser power meter. The painted side of the cell was then glued to a small heat dissipator, facing outwards.

The main case and lid were 3D printed using provided design files. Insertion nuts were added to the case using a soldering iron, allowing for easy assembly and disassembly. The PCB was then inserted into the case and secured with M3 screws.

Wires were connected from the on/off switch to the PCB, and a 4V LiPo battery was added to power the device. The Peltier cell with its heat dissipator was placed inside the case, facing outwards, and wires were soldered to the corresponding pins on the PCB.

Once assembled, the device was calibrated using a commercial laser power meter as a reference. Measurements were taken at various power levels (10%, 20%, 30%, etc.) using both the commercial meter and the homemade device. The readings from the homemade device were then plotted against the actual measured power to create a transfer function.

This transfer function was incorporated into the Arduino code, allowing the device to accurately measure laser power. Future firmware updates are planned to include additional calibration steps, such as room temperature compensation.

Initial tests showed promising results, with the homemade device measuring laser power with similar accuracy to the commercial meter. However, further refinement is needed to address issues related to room temperature and its effect on the measurements.

The project successfully demonstrated that a functional laser power meter can be built at a significantly lower cost than commercial alternatives. The total cost of the DIY project was approximately 1/20th of the price of the commercial meter used as a reference.

All design files, code, and part lists are available for free, allowing others to replicate or improve upon this project. This resource can be particularly useful for hobbyists, educators, and researchers who require accurate laser power measurements without breaking the bank.

Building a $10 Laser Power Meter from Scratch

• 1 x Photodiode (e.g. BPW21 or equivalent)
• 1 x 1kΩ resistor
• 1 x 10kΩ resistor
• 1 x 100nF capacitor
• 1 x Breadboard and jumper wires
• 1 x Multimeter (optional)

1. Connect the photodiode to the breadboard, making sure to note the orientation of the diode (the side with the tab is usually the cathode).
2. Connect the 1kΩ resistor between the anode of the photodiode and a jumper wire.
3. Connect the 10kΩ resistor between the jumper wire and the positive terminal of the multimeter (if using).
4. Connect the 100nF capacitor between the jumper wire and ground.

1. Mount the photodiode on a breadboard or PCB.
2. Connect the op-amp to the photodiode and power supply.
3. Add resistors for gain setting and voltage division.
4. Add capacitors for filtering and coupling.
5. Add diodes for protection and rectification.
6. Connect the display to the output of the op-amp.

• Linearity: ±1% ( typical)
• Sensitivity: 10mV/μW (typical)
• Dynamic Range: 100nW to 100mW
• Accuracy: ±5% (typical)

• Use a more sensitive photodiode for increased sensitivity.
• Add an additional stage of amplification for increased gain.
• Use a logarithmic amplifier for wider dynamic range.
• Integrate the circuit with a microcontroller for digital readout and data logging.