Changes between Initial Version and Version 1 of DeadProjects


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Timestamp:
11/08/13 10:17:53 (4 years ago)
Author:
hazen
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  • DeadProjects

    v1 v1  
     1This page will document a biological compound sensor being 
     2developed for the research group of Profs. Mohanty and Eramilli. 
     3 
     4This device will use a proprietary sensor chip to measure the 
     5concentrations of various biological compounds in an aqueous solution. 
     6 
     7== Open Issues == 
     8 
     9* Mechanics - connector type and pinout for cell connection 
     10 * See [http://joule.bu.edu/~hazen/BioSensor/multisideshow.pdf CAD drawing] 
     11proposed 8-device prototype.  What are the units? 
     12 
     13== Prototype 1 Specifications == 
     14 
     15* Generate a fixed AC stimulus signal of 10mV at 17Hz (sinusoidal) 
     16* Provide a DC bias for ''''V(DS)''' on which AC stimulus is superimposed 
     17with a range of -2V to +2V.  Set in 5mV or smaller steps, 
     18absolute precision to 1mV desirable. 
     19* Provide an analog switch to route the above ''''V(DS)''' combined 
     20AC/DC signal to one of eight electrodes. 
     21* Output a separate DC source for ''''V(GS)''' with same 
     22specs as for ''''V(DS)''' above.  This will set the potential of 
     23an electrode immersed in the solution. 
     24* Provide two additional side-gate bias voltages with an output 
     25range of -5 to +5V (Precision?  Step size?) 
     26* Provide eight analog switches for each side-gate bias voltage 
     27to route the above signals to the desired device. 
     28* Measure the DC and AC currents through the sensor.  The AC current will 
     29be measured using a phase-sensitive detector, converted to a DC signal, 
     30and digitized with an ADC. 
     31 
     32Future versions may also have  
     33variable frequency and amplitude for the AC stimulus. 
     34 
     35== Analog Circuit Implementation == 
     36 
     37The analog interface electronics will be implemented on a custom PC board 
     38which will have a connector on which the sensor cell can plug directly. 
     39 
     40Please refer to the 
     41[http://joule.bu.edu/~hazen/BioSensor/proto_block.pdf block diagram] 
     42The blue lines show the wiring on the device itself, or it''s mounting PC board. 
     43The blue squares represent connection points to the electronics. 
     44 
     45Four DC bias voltages are buffered and driven to the device as shown.  Three analog switches 
     46for each of 8 devices allow bias signals to be selectively applied to one device at a time. 
     47 
     48Readout is via a current-sensitive op-amp circuit, a phase-sensitive detector, DC 
     49amplifier and ADC. 
     50 
     51== Control and Interface == 
     52 
     53We currently plan to purchase an off-the-shelf embedded controller 
     54and A/D interface board.  See links below for some likely options. 
     55We would provide software on the embedded computer to support 
     56setting the analog switches and bias voltages, and measuring 
     57the current with an ADC. 
     58 
     59A simple TCP/IP server or USB equivalent would be provided, 
     60with a very simple DEMO program running on a PC to show 
     61functionality. 
     62 
     63* [http://www.embeddedarm.com/products/board-detail.php?product=TS-7260 TS-7260] 
     64from technologic systems looks like a good bet. 
     65* [http://www.embeddedarm.com/products/board-detail.php?product=TS-ADC16 TS-ADC16] 
     66 board would provide DAC (12-bit) and ADC (16-bit) and digital I/O functions – 
     67[http://joule.bu.edu/~hazen/BioSensor/TS-ADC16%20FPGA%20registers-v2.pdf preliminary manual] 
     68* [http://www.embeddedarm.com/products/board-detail.php?product=TS-9700 TS-9700] 
     69alternative I/O board with 12-bit DAC/ADC functions. 
     70 
     71 
     72