| Version 8 (modified by , 10 years ago) (diff) |
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CW DOSI Probe for Cancer Monitoring
The proposed probe contains six pairs of LEDs, one photo-detector assembly and drive electronics. Each of the 12 LEDs may be selected individually, with external drive current controlling the output intensity.
The LED pairs are arranged in a circle with a 25.4mm radius, with the photodiode assembly in the center.
A single flexible, multi-conductor cable provides power and control. The HDMI cable seems like a reasonable off-the-shelf solution (with mini-HDMI type C connector on the probe)
Initial (Rigid PCB) Design
- Schematic: PDF ExpressPCB
- Layout: ExpressPCB
- Suggested parts:
- 74HCT154 (Digi-Key 568-8858-1-ND) in VQFN 3.5mm x 5.5mm package (Note 1)
- DMN2004DMK-7 dual MOSFET (Digi-Key DMN2004DMKDICT-ND)
Notes:
- The 74HCT154 is attractive because of the very small package, but has active-low logic outputs. This requires a small change in the schematic. The control interface should be unchanged.
Interface Cable
| 1 | PD_C | Photodiode cathode connection |
| 2 | PD_A | Photodiode anode connection |
| 3 | GND-S | Ground shield for Photodiode signal |
| 4 | GND-S | Ground shield for photodiode signal |
| 5 | A0 | LED address bit 0 |
| 6 | A1 | LED address bit 1 |
| 7 | A2 | LED address bit 2 |
| 8 | A3 | LED address bit 3 |
| 9 | EN | LED enable - active low |
| 10 | DGND | Logic GND |
| 11 | VCC | Logic power (3.3V-5V) |
| 12 | DGND | Logic GND |
| 13 | AGND | LED GND (power return) |
| 14 | AVCC | LED power |
