Changes between Initial Version and Version 1 of DeadProjects

Timestamp:

Nov 8, 2013, 10:17:53 AM (10 years ago)

Author:

Eric Hazen

Comment:

--

DeadProjects

@@ +1 @@
+This page will document a biological compound sensor being
+developed for the research group of Profs. Mohanty and Eramilli.
+
+This device will use a proprietary sensor chip to measure the
+concentrations of various biological compounds in an aqueous solution.
+
+== Open Issues ==
+
+* Mechanics - connector type and pinout for cell connection
+ * See [http://joule.bu.edu/~hazen/BioSensor/multisideshow.pdf CAD drawing]
+proposed 8-device prototype.  What are the units?
+
+== Prototype 1 Specifications ==
+
+* Generate a fixed AC stimulus signal of 10mV at 17Hz (sinusoidal)
+* Provide a DC bias for ''''V(DS)''' on which AC stimulus is superimposed
+with a range of -2V to +2V.  Set in 5mV or smaller steps,
+absolute precision to 1mV desirable.
+* Provide an analog switch to route the above ''''V(DS)''' combined
+AC/DC signal to one of eight electrodes.
+* Output a separate DC source for ''''V(GS)''' with same
+specs as for ''''V(DS)''' above.  This will set the potential of
+an electrode immersed in the solution.
+* Provide two additional side-gate bias voltages with an output
+range of -5 to +5V (Precision?  Step size?)
+* Provide eight analog switches for each side-gate bias voltage
+to route the above signals to the desired device.
+* Measure the DC and AC currents through the sensor.  The AC current will
+be measured using a phase-sensitive detector, converted to a DC signal,
+and digitized with an ADC.
+
+Future versions may also have 
+variable frequency and amplitude for the AC stimulus.
+
+== Analog Circuit Implementation ==
+
+The analog interface electronics will be implemented on a custom PC board
+which will have a connector on which the sensor cell can plug directly.
+
+Please refer to the
+[http://joule.bu.edu/~hazen/BioSensor/proto_block.pdf block diagram]
+The blue lines show the wiring on the device itself, or it''s mounting PC board.
+The blue squares represent connection points to the electronics.
+
+Four DC bias voltages are buffered and driven to the device as shown.  Three analog switches
+for each of 8 devices allow bias signals to be selectively applied to one device at a time.
+
+Readout is via a current-sensitive op-amp circuit, a phase-sensitive detector, DC
+amplifier and ADC.
+
+== Control and Interface ==
+
+We currently plan to purchase an off-the-shelf embedded controller
+and A/D interface board.  See links below for some likely options.
+We would provide software on the embedded computer to support
+setting the analog switches and bias voltages, and measuring
+the current with an ADC.
+
+A simple TCP/IP server or USB equivalent would be provided,
+with a very simple DEMO program running on a PC to show
+functionality.
+
+* [http://www.embeddedarm.com/products/board-detail.php?product=TS-7260 TS-7260]
+from technologic systems looks like a good bet.
+* [http://www.embeddedarm.com/products/board-detail.php?product=TS-ADC16 TS-ADC16]
+ board would provide DAC (12-bit) and ADC (16-bit) and digital I/O functions –
+[http://joule.bu.edu/~hazen/BioSensor/TS-ADC16%20FPGA%20registers-v2.pdf preliminary manual]
+* [http://www.embeddedarm.com/products/board-detail.php?product=TS-9700 TS-9700]
+alternative I/O board with 12-bit DAC/ADC functions.
+
+
+