SP02 Finger Clip - jaredwhichard/Capstone-Website GitHub Wiki

When we began working with the MAX30102 sensor during the planning phase, we were alarmed by inconsistent readings from the device. We researched this and learned that there are a variety of factors that can impact the accuracy of our sensor. The first of these factors is light, SP02 sensors operate by emitting an IR light through the skin, then recording the density and time between pulses via an IR receiver. If the receiver picks up external light, the results can be impacted. Another factor is pressure due to the constriction of bloodflow. With uneven pressure, the sensor may read spikes or very low pulse levels. In order to block light and keep even pressure on the sensor, we need to create a clip.

Printing the Clip

We were able to find a 3D design of a finger clip that fits our sensor on Thingiverse After getting access to a 3D printer we printed out the two pieces for the clip.

Installing the Sensor

One of the two pieces is designed with a relief for the sensor to sit in, with a small wiring track for the output to rest in. We needed to remove the testing headers from the sensor in order for it to fit within the relief and solder the wires directly to the sensor. We then attached the sensor to the bottom half of the clip using hot glue.

Assembling the Clip

With the sensor attached to the bottom half of the clip, screw the halves together at the pivot using two 10mm self-tapping screws. This allows the clip to pivot and close which will block most external light, but it still does not provide adequate tension. There is a relief in the device facing side of the clip for a spring, ideally, it is designed for a 6mm x 30mm spring but a pen spring can be substituted.