1. Introduction
This automated test strip analyzer will be one of some additonal peripherals for the Medical tricorder Mark II. We will make use of commonly available urine test strips. The test strips I am using are for semi-quantitative and qualitative detection of asorbic acid, glucose, bilirubin, ketone, blood, protein, urobilinogen, nitrite, leukocytes, pH and specific gravity in urine. These kind of test strips can help to diagnose diseases such as urinary tract infection, kidney disease, and diabetes.
Fig. 1 dBest® urine test reagent strips I purchased on taobao
The hardware of the test strip analyzer will mainly consists of a linear actuator (slider) and a TCS34725 based color sensor. On software side I will use a kNN algorithm beside of other supervised machine learning tools to classify and validate the detected colors.
2. Hardware
2.1 Test strip carrier
As usual I start a project with some sketches. The images below show the test strip carrier and how the test strip will be fixed on the carrier. SketchUp 2014 was used for the model.
Fig. 2 Test strip carrier
Fig. 3 Clamping mechanism
Fig. 4 Test strip fixed on carrier
2.2 Linear actuator
I purchased several linear actuators on taobao. These linear actuators might also be useful for other projects.
Fig. 5 Linear actuator
Technical data:
- Motor: Stepper, bipolar, 4-6V, 300 mA, 15Ω per coil, motor dia.: 15mm
- Screw length: 90mm
- Screw pitch: 0.5mm
- Screw dia.: 3mm
- Slide stroke: 80mm
Next a bipolar stepper motor driver PCB [1] was designed and the linear actuator modeled for further design steps.
Fig. 6 Bipolar stepper motor driver schematic
Fig. 7 Bipolar stepper motor driver PCB design
Fig. 8 Model of the linear actuator
3. References
[1] http://www.tigoe.com/pcomp/code/circuits/motors/stepper-motors/