This Thermistor solution is based on a calibrated Wheatstone bridge. The Voltage potential over the thermistor is measured and compared to a fixed voltage divider. Three thermistors can be measured using the micro controllers internal analog to digital converter. In order to achieve accuracy, the ADC is run a audio frequencies and measurements are averaged. Although ESP32 internal ADC is not of high quality, with the help of linearization and signal averaging, accurate temperature readings are achieved.
| Item | Quantity at Purchase | Costs | Source | Cost per Brick |
|---|---|---|---|---|
| Microcontroller | 1 | $17.5 | Adafruit | $17.5 |
| Display | 5 | $13 | Amazon | $3 |
| Button | 25 | $9 | Amazon | $0.5 |
| Battery | 1 | $10 | Adafruit | $10 |
| PCB | 5 | $45.20 | PCBWay | $9 |
| Parts and Assembly | 2 | $99.16* | PCBWay | $50 |
| Thermistors MA1000GG103AN ** | 1 | $6 | Amphenol | $6 |
| 3.5mm male audio connector | 10 | $10 | Amazon | $1 |
| Assorted Wires | 8m | $15 | Amazon | $1 |
| Assorted Screws and Nuts | 100 | $7 | Amazon | $0.05 |
| Assorted 3D printed parts | $3 | |||
| Total | $100 |
*Electronic components are $12 per board.
**MA100BF103 also comes in less accurate and less expensive versions: MA100BF103BN and MA100BF103CN.
Test software is located in the Arduino folder.
| Folder | Description |
|---|---|
| MediBrick_Temperature_Test | Computes calibrated temperature. |
Not finalized yet
The following files are needed for PCB manufacturing and assembly.
The Bill of Materials is formatted so that its compatible with PCBWay submissions.
These are the links to the OnShape Design files, which you can edit and modify if you have an OnShape account (OnShape has free academic accounts).