| Version 30 (modified by , 9 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
- Parts list: proto1_BOM.xlsx
Revised (Flex PCB) Design
- Second Layout
- KiCAD (FINAL): http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/FlexV2/CWProbe2_Final.zip (gerber files included)
- Schematic (FINAL): PDF
- Parts List (FINAL): XLS
- Preliminary Layout
- KiCAD (PREVIEW): CWProbe.zip
- Gerbers (PREVIEW): CWprobeV1.zip
- Schematic: schematic.pdf -- Preview draft 2014-10-15
- Layout: TOP BOTTOM -- Preview draft 2014-10-15
- Suggested parts:
- Photodiode: S4797 (Hamamatsu, low profile SMT)
- LED 850nm: smt850-23.pdf (low profile SMT)
- LED 750nm: smt750-23.pdf (low profile SMT)
- 74HC4514 decoder in TSSOP24 package (original)
- 74HCT154 (Digi-Key 568-8858-1-ND) in VQFN 3.5mm x 5.5mm package (Alternative, see Note 1)
- DMN2004DMK-7 dual N-channel MOSFET (Digi-Key DMN2004DMKDICT-ND)
- DMP2004VK-7 dual P-channel MOSFET
- uHDMI connector -- WM1280CT-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. Alternatively, the 4514 decoder is available in a TSSOP24 package which is about 7mm x 8mm
Interface Cable
Proposed pinout for micro HDMI
| Pin | HDMI Use | DOSI Use | Notes |
| 1 | Hot Plug Detect/HEAC- | ||
| 2 | Utility/HEAC+ | ||
| 3 | TMDS Data2+ | Photodiode+ | Photodiode Anode |
| 4 | TMDS Data2 | Photodiode GND | Shield for Photodiode signal |
| 5 | TMDS Data2- | Photodiode- | Photodiode Cathode |
| 6 | TMDS Data1+ | LED Power | Power for LEDs |
| 7 | TMDS Data1 Shield | AGND | Shield for LED power |
| 8 | TMDS Data1- | AGND | Ground for LEDs |
| 9 | TMDS Data0+ | A0 | Address 0 |
| 10 | TMDS Data0 Shield | DGND | Logic GND |
| 11 | TMDS Data0- | DGND | Logic GND |
| 12 | TMDS Clock+ | LE | Latch enable |
| 13 | TMDS Clock Shield | DGND | Logic GND |
| 14 | TMDS Clock- | DGND | Logic GND |
| 15 | CEC | A1 | Address 1 |
| 16 | DDC/CEC/HEAC Ground | DGND | Logic GND |
| 17 | SCL/DDC clock | A2 | Address 2 |
| 18 | SDA/DDC data | A3 | Address 3 |
| 19 | +5V power | VCC | Logic power (3.3V-5V) |
