In the BIOZ and ECG MediBrick we use the MAXIM MAX30001G analog front end (AFE). It's a modern IC with a "waver level packaging" foot print which makes is difficult to solder and requires precise PCB manufacturing.
The MAX30001G can measure:
- Biopotential
- ECG (waveform)
- R-R Time (heart rate and heart rate variability)
- Bioimpedance
- Resp (respiration rate)
- GSR (galvanic skin response, stress level)
- EDA (electro dermal activity)
Here MAX3001G we summary capabilities from the datasheet.
For general consideration of bio impedance design and safety: Analog Devices: Bio-Impedance Circuit Design for Body Worn Systems"
| 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 | $145.80 | PCBWay | $29 |
| Parts and Assembly | 5 | $186.42 | PCBWay | $38 |
| Assorted Wires | 8m | $15 | Amazon | $1 |
| Assorted Screws and Nuts | 100 | $7 | Amazon | $0.05 |
| Assorted 3D printed parts | $3 | |||
| ECG 3.5mm cables | 1 | $5.50 | Sparkfun | $5.50 |
| Electrodes (consumable) | 100 | $25 | Amazon | $ 1 |
| Total | $110 |
Electronic components are $20 per board. Because of WLP foot print of MAX30001G the PCB is 3 times as expensive as the other PCBs.
Test software is located in the Arduino folder.
| Folder | Description |
|---|---|
| MAX30001G Driver | under development |
| Test programs | not available yet |
Not available 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).
We have the following external connectors:
-
ECG, 3,5mm audio
- ECG_N (middle of plug) e.g. left arm
- ECG_P (proximal side of plug) e.g. right arm
- VCM/ECG_GND (common mode) (tip of plug) e.g. leg
-
Impedance, 3.5mm audio
- BI_N
- BI_P
- GND (tip of plug)
-
Driver, 3.5mm audio
- DRV_P
- DRV_N
- GND (tip of plug)
- We can operate the board to measure ECG or Impedance or both.
- We can operate the board to use only two leads, four leads or six leads.
- 6 leads ECG on ECGP & ECGN, BIOZ on BINP & BINN and DRV on DRVP & DRVN
- 4 leads ECG on ECGP & ECGN, BIOZ on BINP & BINN
- 2 leads ECG, BIOZ, DRV on ECGP & ECGN
- We can configure the board to measure impedance of a calibration resistor that is soldered onto the board (100 Ohm).
Typical values and conditions of external components
| Name | typical value | Comment |
|---|---|---|
| C_ECG | 2.2nF | datasheet |
| C_ECG-G | 10pF | datasheet, 47pF protocentral |
| EP_EN | open | if closed disable ECG |
| R_ECG | 0,51k,200k Ohm | 0, 200k shown in datasheet (200k when ECG conencted with BIOZ), 51k protocentral, 0 Ohm evaluation kit |
| R_ECG-B | 51k | evaluation kit |
| C_ECG_B | 47nF | evaluation kit |
| ECG_UNBAL | open | if closed disable balancing |
| EP_BP | open | impedance and ECG is on different plug |
| EN_BN | open | impedance and ECG is on different plug |
| C_BIN | 47pF | datasheet |
| C_BIN_G | 10pF | datasheet |
| BP_BN | open | if closed disable BioZ |
| R_BIN | 0, 200 Ohm | 200 protocentral where ECG is connected to BIN, 0 evaluation kit |
| R_CAL | 100 Ohm | evaluation kit |
| RP | open | if closed no external impedance |
| RN | open | " |
| BP_DP | open | impedance and driver on different plug |
| BN_DN | open | impedance and driver on different plug |
| C_DRV | 200nF, 47nF | 47nF protocentral, 47nF evaluation kit |
| R_VCM | 0 Ohm,10k,200k | 10k protocentral, evaluation kit has buffer driver circuit, 200k datasheet |
| R_VCM-B | 51k, none | none protocentral & evaluation kit |
| C_VCM-B | 47nF, none | none protocentral & evaluation kit, 47nF datasheet |
| VMC_UNBAL | open |