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3D-Printable Raman Spectrometer

The only thing worth doing, is the thing worth doing right!

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The DAV5 V3 Spectrometer will be the only project build here on Hackaday in its category, with ongoing, full performance and specifications documentation, this project will also be at least 95% 3D printed! The main goal for this project has 4 points:

1) To build a rugged and reliable low cost spectrometer with 3D printable parts.

2) A spectrometer capable of producing consistent and professional quality results in the field, home or Lab

3) A device with upgradeable capabilities

4) Every part of this project will have it's .STL file (for 3D-printing,) available for download.

**This project will also have full professional/analytical and chemical documentation.

***This project is in NO way related to, or in anyway, conceptualized to replicate the 3D Raman-Pi project here at Hackaday.***

This is my projects MISSION STATEMENT:

This is the primary motivation for doing this project from its inception over a year ago to present day, I specialize in biological pigments and dyes. This is the ultimate direction that this project will be moving toward. Nanoparticles used as bio tags for an unprecedented level for cellular targeting eliminating the need to use the conventional methods of bio staining.

Reference:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC419715/

*UPDATE* 3/11/2017 4:55AM

The LS-532A-laser collimation tube assembly, is my design and build. I have assigned it this nomenclature for easy identification.

Here are the three components that will be a critical part of the CCD driver circuit, so I wanted to post a general feature and description of them, starting with the AD8021 opamp (which will be used as the pre amp for the ADC (AD7667)

GENERAL DESCRIPTION

The AD8021 is an exceptionally high performance, high speed voltage feedback amplifier that can be used in 16-bit resolution systems. It is designed to have both low voltage and low current noise (2.1 nV/√Hz typical and 2.1 pA/√Hz typical) while operating at the lowest quiescent supply current (7 mA @ ±5 V) among today’s high speed, low noise op amps. The AD8021 operates over a wide range of supply voltages from ±2.25 V to ±12 V, as well as from single 5 V supplies, making it ideal for high speed, low power instruments. An output disable pin allows further reduction of the quiescent supply current to 1.3 mA.

*UPDATE* 3/27/2017 5:54:AM

I eliminated the MAX232EIN from the circuit equation, it cannot handle the load placed on it from the AD8021 op amp, so it is going to be replaced by the MAX660 - Switched Capacitor Voltage Converter. The MAX660 CMOS charge-pump voltage converter is a versatile unregulated switched-capacitor inverter or doubler. Operating from a wide 1.5-V to 5.5-V supply voltage, the MAX660 uses two low-cost capacitors to provide 100 mA of output current without the cost, size and EMI related to inductor based converters. With an operating current of only 120 µA and operating efficiency greater than 90% at most loads, the MAX660 provides ideal performance for battery-powered systems. MAX660 devices can be operated directly in parallel to lower output impedance, thus providing more current at a given voltage. The FC (frequency control) pin selects between a nominal 10-kHz or 80-kHz oscillator frequency. The oscillator frequency can be lowered by adding an external capacitor to the OSC pin. Also, the OSC pin may be used to drive the MAX660 with an external clock up to 150 kHz. Through these methods, output ripple frequency and harmonics may be controlled. Additionally, the MAX660 may be configured to divide a positive input voltage precisely in half. In this mode, input voltages as high as 11 V may be used.

http://www.ti.com/lit/ds/symlink/max660.pdf

AD7667

FEATURES

2.5 V internal reference: typical drift 3 ppm/°C Guaranteed max drift 15 ppm/°C Throughput: 1 MSPS (Warp mode) 800 kSPS (Normal mode) 666 kSPS (Impulse mode) INL: ±2.0 LSB max (±0.0038% of full scale) 16-bit resolution with no missing codes S/(N+D): 88 dB min @ 20 kHz THD: –96 dB max @ 20 kHz Analog input voltage range: 0 V to 2.5 V No pipeline delay Parallel and serial 5 V/3 V interface SPI®/QSPITM/MICROWIRETM/DSP compatible Single 5 V supply operation Power dissipation 87 mW typ @ 666 kSPS, 130 µW @ 1 kSPS without REF 133 mW typ @1 MSPS with REF 48-lead LQFP and 48-lead LFCSP packages Pin-to-pin compatible with AD7671, AD7677

GENERAL DESCRIPTION

The AD7667 is a 16-bit, 1 MSPS, charge redistribution SAR analog-to-digital converter that operates from a single 5 V power supply. The part contains a high speed 16-bit sampling ADC, an internal conversion clock, internal reference, error correction circuits, and both serial and parallel system interface ports. It features a very high sampling rate mode (Warp), a fast mode...

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CCD circuit driver 4 FEB26.asc

Main CCD driver circuit schematic/TCD1304AP

asc - 8.82 kB - 03/05/2017 at 16:34

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Exploded view TCD1304 100 ohm fix to MCU mar5.asc

Revision C for modification on 100 ohm resistors in series with ICO, MCLK and SH leads to D13, D16 and D14 connections at MCU (ATmega1284 development board.)

asc - 876.00 bytes - 03/05/2017 at 16:34

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switch debouncer SIM mar 3.asc

*UPDATED* 3/4/2017 Added switch debouncer at S1 on main schematic for CCD driver circuit for the Toshiba TCD1304AP.

asc - 1.44 kB - 03/04/2017 at 13:28

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ad8021 sim.asc

*UPDATED @ 6:53PM 3/2/2017* LTspicemodel sim for the AD8021 opamp

- 2.77 kB - 03/02/2017 at 23:53

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6417.asc

LTC6417 op amp

asc - 2.12 kB - 03/01/2017 at 19:12

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FIXED cuvette holder FEB 2 (Meshed).stl

*UPDATED: 2/5/2017 re-designed the Raman filter slot again, I found a less expensive Raman edge filter at Thorlabs that will work just fine, so the new slot is now 25.5 x 4.45mm and 39mm deep so the filter is at 12.5mm center line.

Standard Tesselated Geometry - 1.41 MB - 02/05/2017 at 13:12

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25 x25 x 6mm diffraction hologrphc done (Meshed).stl

UPDATE 1/17/2017:Holographic Diffraction grating mount holder. Dimensions; 27 x 27x with a 6mm width slot for grating mount. Inlayed 2mm at slot bottom.

Standard Tesselated Geometry - 597.64 kB - 01/17/2017 at 23:07

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40mm Lens Holder Coupler assembly fixed (Meshed).stl

UPDATE 1/17/2017:Widened the dia. of the coupler and inner dia. the 3D printing came out with a little shrinkage so I had to fix that.

Standard Tesselated Geometry - 376.74 kB - 01/17/2017 at 23:07

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20mm dia locking sleeve (Meshed).stl

lens locking sleeve for 2nd lens chamber

Standard Tesselated Geometry - 98.71 kB - 12/22/2016 at 20:57

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ALL mounting holes cut dec 16 main enclsr (Meshed).stl

Re-designed Main enclosure, 203 X 152 X 74 mm without Lid. All mounting holes are pre-cut and exactly placed.

Standard Tesselated Geometry - 5.08 MB - 12/16/2016 at 21:03

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View all 14 files

  • 1 × Cuvette Holder W/ Exit slit plate Dimensions; 45 X 45 X 25 mm / 3D-printed by Sculpteo
  • 1 × (2) Square Mirror Mounts 26 X 13 X 26 mm
  • 1 × Round standoff M3 Nylon 13mm
  • 1 × Round standoff M3 Brass 11mm Used for enclosure
  • 1 × Machine screw Pan head phillips M3
  • 1 × Machine screw Pan head phillips M4
  • 1 × JDEPC-ov05 CMOS webcam (board level type) USB 2.0 free driver included, S/N ratio >39dB, 60mm L X 8mm W X 6.6mm H cmos 2mega pixel JPEG video compression
  • 1 × Orion 8728 32mm Sirius Plossl Lens 54 degree field of view. dimensions; 50mm length X 31.7mm barrel dia.
  • 1 × Schott Glass filter (ThorLabs) ROHS compliant (2011/65/EU) Mounted 025.0mm 280nm, longpass Color filter - Cost - $49.15US
  • 1 × (2) 50.8mm Square Silver Mirror (protected silver coated) ROHS compliant: 3.2mm thickness (2011/65/EU) Cost - $43.50US 2 ea.

View all 19 components

  • 555 Timer Pulse Generator @ Approx 1020 Hz

    David H Haffner Sra day ago 0 comments

    I put together a simple pulse generator, using a 555 timer chip from a schematic from an old Forest Mims notebook of mine, so I could calibrate the MCU and MegunoLink Pro to work together when I get ready to link the CCD to the ATmega1284.

    These are the results below and they are beautiful :)

    Final Plot, 4.47vdc @ 0.26mA

    Code used for this test;

    #include "MegunoLink.h" // Helpful functions for communicating with MegunoLink.

    // Millis value when the data was last sent.

    long LastSent;

    // Interval (milliseconds) between sending analog data

    const unsigned SendInterval = 200; // [ms]

    // The plot we are sending data to.

    TimePlot MyPlot;

    void setup()

    {

    Serial.begin(115200);

    LastSent = millis();

    MyPlot.SetTitle("PulseTestProgram");

    MyPlot.SetXlabel("Frequency Hz");

    MyPlot.SetYlabel("MilliSeconds");

    MyPlot.SetSeriesProperties("GeneratorValue", Plot::Magenta, Plot::Solid, 2, Plot::Square);

    }

    void loop()

    {

    if ((millis() - LastSent) > SendInterval)

    {

    LastSent = millis();

    int DataValue = analogRead(PA0);

    MyPlot.SendData("GeneratorValue", DataValue);

    }

    }

    This plot is using a 10k Pot @ 4.53vdc

    Pulse at 4.98vdc

    Pulse at 4.13vdc

    Pulse at 4.27vdc

  • XR2206 Function Generator/Experiment for setting up serial plotter for TCD1304 CCD Graphing Plot

    David H Haffner Sr5 days ago 0 comments

    *UPDATE* 3/26/2017 9:03:AM

    I scrapped my plans for using SerialPortPlotter because writing the routine just was not working out right, between the code for the CCD detector and the serial port, so I searched for a few hours and found the perfect match up, MegunoLink Pro, http://www.megunolink.com/ it has the capability of allowing me to customize my serial interface and the CCD control program in a seamless manner.

    I downloaded the free trial and tested it out and immediately it connected and I was monitoring data output, very cool :) It also allows me to log data to a file automatically.

    The biggest advantage of this new program will be the ability to write a control program for live capture and calibration of the spectral data in real time and shoot it off in csv file format without having to swim the English channel to get their.

    I have a program called "serialportplotter," which is really nice, and has a routine I can modify for using it as the main plotter for downloading the data from the CCD detector. I need it because it is easy to convert the data to csv file format, I know Arduino serial plotter can do this also, but it can only trace 500 data points and I have to copy and paste the data, I no likey that!

    So I put together a quick function generator from an old XR2206 chip I had, with a 12vdc pwr supply, so I could at least display a couple of waveforms easily and test my modified routines out in C, for SerialPortPlotter.

    I included a short little video showing a simple square wave from Arduino's serial plotter to make sure that I put the circuit together right, and walla, I did!

    http://photos.google.com/photo/AF1QipOj-owuNBgY702v2rmQV8QoVBTvQ_Z94UwIPND0

    Well, this is it;

    This is the ATmega1284P development board form MCUdude that I bought from the Tindie store;

  • REV C / TCD1304AP - CCD Detector Module (DAV5 V3 Raman Spectrometer)

    David H Haffner Sr03/22/2017 at 08:57 0 comments

    *UPDATE* 3/23/2017 4:59:AM

    Ok, I tried to outsmart the AD7667, the LM318p is NOT going to work for the simple reason that the slew rate is too small (50 V/um) even with REV C, the slew rate is still only 70 V/um. The AD8021 has a slew rate of 120 V/um, upon testing the CCD output using the serial plotter, the signal was very "jumpy." (also the LM318's bandwidth is too small, 15MHz.)

    Also the MAX232 was getting very hot and I can't afford the ADC getting damaged, so back to placing the AD8021 in it's rightful place. I will have to re-design component placements and get everything to fit on a 99 X 53.2 mm board.

    I had to make a major modification to the CCD detector module this week, the leads were too long coming from the ADC to the MCU, so I had to completely de-solder the boards and reconfigure them on one board.

    A double sided type configuration, very tedious, but worth it. I got everything on both sides and replaced the AD8021 op amp with the LM318P REV B op amp, reason for this is the ad8021 is so very small and hard to work with, so I sacrificed some speed and bandwidth on the video side of things and the LM318 will provide the same function and low noise, with greater stability for the MAX232.

    I sacrificed a little bandwidth at the pre-amp side for the ADC, by placing a 10pf cap at pin 5 of the op amp (the data sheet calls for a 7pf, but I need a little more stability,) so I cut the bandwidth down a bit but increase over all stability of the video output, and the MAX232 can handle the load, and I can still operate at 5vdc.

    This is the back end view showing the ADC and MAX232.

    A close up shot of the AD7667 (ADC)

    Below is the TCD1304AP CCD chip module and LM318P op amp

  • Module 1/TCD1304AP Complete/Module 2/AD7667 Complete

    David H Haffner Sr03/12/2017 at 21:34 0 comments

    Well exactly 98 man hours later, (avg. 14hrs per day*7,) and These are the 2 primary modules and I included the CLI (communication link interface) I had to make this so I could connect the CCD module with the ADC module.

    This is the CCD module (1)

    This is the ADC, module (2) Top view

    Below is the bottom view

    This is the CLI, Top view (which will be connected to the inside front face of spectrometer

    Below is the backside view of CLI, CCD module (1) connects to terminal on the left and above view, the 2 x 6 dual terminal with the power indicator LED, faces toward user for connection to MCU and ADC module.

    This is the top cover of the MCU chassis, the trigger switch is already in place with the science frame indicator LED visable

    Close up view of the trigger switch circuit

    Below is the backside view of the switch already mounted in place

    In case you were wondering why there is a 14 pin DIP socket securing the switch? Well, this is a little blast from my past, it was suppose to be a project for a function generator and evidently I never finished it, so I decided to put it to good use anyway :)

  • *UPDATE* Change made To The MCU/ATmega1284 REV B

    David H Haffner Sr03/10/2017 at 09:33 0 comments

    I removed the 1st breadboard strip I had in place as my terminal junction, and used this configuration instead. This makes more sense and gives me room to employ the necessary 100 ohm resistors and other terminals.


  • Work Started On The TCD1304 Proto-board/ADC (AD7667) Proto-board

    David H Haffner Sr03/10/2017 at 00:37 0 comments

    These are the major components soldered in place on the TCD1304AP proto board. This is the 1st board facing the 2nd focal mirror.

    This is a closeup view showing the MAX232EIN and the placement of the AD8021A op-amp.

    This is the ADC (AD7667AP) placed on a 48 pin Schmartboard. This will be positioned on a 2nd proto board behind the 1st board with a 6 pin dual row terminal for the TCD1304 which will interface separately on the MCU and the rest of the terminating pins on the ADC will have their separate terminal at the MCU.

  • Assembling The ATmega1284/MCU CHASSIS CASE / SEC I

    David H Haffner Sr03/08/2017 at 17:15 0 comments

    These are the first assembly pics for the ATmega1284P/MCU (development board courtesy of MCUdude @Tindie ) http://www.tindie.com/products/MCUdude/dip-40-arduino-compatible-development-board/

    The main controller hardware will be housed in a

    1598-BSGY

    GREY CHASSIS CASE 5.26" X 5.3" X 2"

    The board when shipped, comes with an ATmega32 already to go, so I just removed that and replaced it with the ATmega1284 and burned the bootloader, everything so far, seems ok with the new chip.

  • Final Schematic/CCD Driver Circuit/TCD1304AP REV C

    David H Haffner Sr03/05/2017 at 16:33 0 comments

    This is the final schematic design for the CCD driver circuit, this design was originally made by David Allmon at http://davidallmon.com/pages/ad7667-spectrograph , I have made my own mods because it has to work with my spectrometer, but the circuit works fine. David has emailed me and verified that it works, and that my modifications are fine also, so a big green light!

    When I get the rest of my parts in, I will be documenting the build, because there are a few more mods to make so both the TCD1304 circuit and MCU can interface together.

    The .asc files will be available on my files page for all schematics for download (LTspice.)

  • Added Switch Debouncer @ S1 on Schematic/CCD Driver Circuit

    David H Haffner Sr03/04/2017 at 13:25 0 comments

    *UPDATE* 3/4/2017 3:16:PM

    I redid the SIM for the switch debouncer for S1, I included the LED indicator with its resistor to make sure the values stayed the same, do not mind the component at U1, I included it there because I needed a component to complete the circuit when it is closed and the components in the .LIB files are not cuttin' it. So it's just there to complete the circuit.

    I added a simple single trigger switch debouncer at S1 on the main schematic for the CCD driver circuit, because this is the last stop where the frame data is waiting for upload.

    The 220uf cap is to lock out S1 for 1 second after the pulse, since there will be another frame waiting in the wings.

  • *UPDATED SIM* LTspicemodel/ AD8021 re-configured...

    David H Haffner Sr03/02/2017 at 23:52 0 comments

    Here is the new spicemodel sim, I experimented with several resistor schemes to get the 9.09k value at R5 on the schematic and settled on 2 resistors; 1.5k and a 7.5k in series at R5. This takes care of that ringing spot on the rise time in the SIM. (the .ASC file will be updated on my page.)

View all 75 project logs

  • 1

    These are the build instructions for my LS-532 CB/fiber optic laser collimation tube;

    New Holographic diffraction grating holder assembly.W/drawings:

    The newly re-designed parts came in so I began to prep them and wanted to include them here under build instructions;

    These are the first preliminary drawings and CAD blueprints depicting several aspects in the assembly design and by no means is this the final assembly steps;

  • 2

  • 3

    10X Lens Holder Base assembly and holder design W/ slide rail feature:

View all 13 instructions

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Discussions

David H Haffner Sr wrote 03/09/2017 at 12:26 point

@fl@C@ , I did not mean to offend your project, my thoughts about your methodology are just my opinion, not a rant about my superior intellect. You made a few bold claims about your devices capabilities and did not provide enough documentation to support them, that's all I was getting at. 

In the scientific spectrum, there is always a clear trail of evidence that others should be able to follow in order to verify claims made, and to all experiments. 

Your project is quite extraordinary,

no doubt, but there are several flaws in some of the capabilites that you claim that it can do. As far as utilizing some of your design concepts, very few, the 3D prints are my own design, the Czerny-Turner configuration is just good science, the CCD detector and MCU, are NOT your design, so get over that. 

The .src code I am using is not yours either. When I talk about "full" documentation, that's exactly what I mean, not only the mechanical side of things, but the chemistry and spectroscopy side of things also...The process, that's what is important. Yes, the long boring techy stuff, the stuff like, what standard did you use to calibrate and verify your spectrometer? Did you use holmium Oxide?

Because when all is said and done, that is what I'll be using (and I'm going to have to make the $$ sacrifice of about $450.00US,) to verify that my spectrometer is on point and ready to go. I'm not recommending that anyone else has to do this, I'm doing it because I want this project to reflect my commitment to excellence.

Let me explain once more this projects details:

The DAV5 V3 Spectrometer will be the only project build here on Hackaday in its category, with ongoing, full performance and specifications documentation, this project will also be at least 95% 3D printed! The main goal for this project has 4 points: 

1) To build a rugged and reliable low cost spectrometer with 3D printable parts. 

2) A spectrometer capable of producing consistent and professional quality results in the field, home or Lab 

3) A device with upgradeable capabilities 

4) Every part of this project will have it's .STL file (for 3D-printing,) available for download. 

**This project will also have full professional/analytical and chemical documentation.

**Also as an aside, I have owned my Aries 532nm Green laser (150mW) for over 4 years,) so I did not rip that idea off either.

  Are you sure? yes | no

Loki wrote 03/03/2017 at 12:07 point

Especially with many cell phone cameras enabling access to RAW format images from their cameras (iPhone 6 and newer, many androids), is there any reason not to skip the CMOS all together, and use a cellphone camera; and also use it for the image processing?  Essentially, just have the light source, slit, diffraction, and raman filter in this device, and design it to mate to a cell phone camera?  That would give 8MP+ of resolution.

  Are you sure? yes | no

David H Haffner Sr wrote 03/03/2017 at 12:23 point

Well Loki, the problem with that idea is, cmos has a spectral limit of 1100nm, (metal oxide,) Raman spectroscopy requires a set up like the Czerny-Turner configuration. Also you need a stable laser source coupled with an appropriate bandpass filter.  

  Are you sure? yes | no

Loki wrote 03/03/2017 at 12:54 point

I think that's what I just said.  When I said "device", I meant external device: all the parts of this project (or the Montoya one), except for the CMOS camera and image pipeline.

  Are you sure? yes | no

David H Haffner Sr wrote 03/03/2017 at 13:01 point

"and design it to mate to a cell phone camera?  That would give 8MP+ of resolution."
you stated the above though, and that's what I was going by, if I misunderstood sorry.

  Are you sure? yes | no

Loki wrote 03/03/2017 at 13:07 point

No, that is correct.  Instead of using an older DSLR such as is used in the Montoya design, use a modern cell camera.

Could you explain more about why the CMOS spectral limit is a problem?  perhaps that's what I don't understand, in light of a CMOS sensor being successfully used in the Montoya design.

  Are you sure? yes | no

David H Haffner Sr wrote 03/03/2017 at 14:18 point

It all comes down to photons interacting with silicon. cmos if you are not familar, are 1000's of microscopic photo diodes, photons with an energy above 1.1eV will not necessarily interact with silicon. Their probability interaction depends on how much higher than the 1.1eV band gap the energy of the photon is, this defines an absorption coefficient  [cm-1] depending on the wavelength and the type of material.

This absorption coefficient defines which percentage of the photons entering a one centimeter material will be absorbed. 

To make it even simpler, silicon as a material substance, will only by its own nature, absorb so many photons no matter what, and it just so happens that the limit is approximately 1125nm.

So, as long as you are willing to stay around the 400 - 700nm range in the spectrum you'll be fine...see my point?





  Are you sure? yes | no

Loki wrote 03/03/2017 at 14:32 point

If we're going for stokes raman:

"Raman signals excited by a 532nm laser are distributed in the visible range, where the response is best for most silicon-based CCD chips. Meanwhile, Raman signals from 785nm systems fall within the NIR range (750-1050nm), where the response is still relatively good. For 1064nm, however, typically there is no response from the CCD above 1100nm" (http://bwtek.com/wp-content/uploads/2015/07/raman-laser-selection-application-note.pdf).

As long as we use a 532nm laser, the resulting stokes radiation we need to detect stays in the visible range - which would seem to allow for the use of a CMOS camera.  Also, to get around issues with low signal intensity, why are people sticking with 150mw range lasers, when so much higher power lasers are available for approximately the same cost?

  Are you sure? yes | no

David H Haffner Sr wrote 03/03/2017 at 15:07 point

Yes, you are correct about that, as I stated; as long as you stay within the boundaries of 400-700nm, a 532nm CW laser at at least 150mW will work. The reason I changed up my design scheme was that at 532nm for that particular set up would not have been very effective for analytical Raman spectral work of liquid mediums.

This type of Raman spectroscopy works best at the reflectance level, and I just didn't want to drastically re-design the whole system to accommodate it. Too many more parts and 3D printed parts, more headaches :( 

Ok, typical 785nm Raman spectroscopy is just NOT feasible for a cmos camera, after 700nm the spectrum gets very "scraggly," unpredictable and very unusable. http://www.aphesa.com/documents.php?class=wp - click on the pdf file that says; "Spectral Response of Silicon Sensors"

  Are you sure? yes | no

finstp wrote 02/28/2017 at 21:57 point

There is a very simple design for a home-made 3D printed Raman spectrometer in the literature, complete with very nice example spectra.

See 'A Homemade Cost Effective Raman Spectrometer with High Performance' by EH Montoya, A Arbildo and OR Baltuano published in Journal of Laboratory Chemical Education 3(4) p 67-75, (2015) doi:10.5923/j.lce.20150304.02. This could easily be coupled with the Spekwin32 software (see here on Hackaday), which can extract a linescan spectrum from the digital camera image and you have all the benefits of professional software too!

  Are you sure? yes | no

Mid-Ohio Area Robotics wrote 01/18/2017 at 01:32 point

This is actually really really awesome. Battelle is a defense contractor here in the states, they sell a biohazard detector that is pretty large for a lot of money, this thing can be made for a fraction of that cost and easily applied to do biohazard detection. Great work!

  Are you sure? yes | no

David Challener wrote 01/13/2017 at 19:19 point

I have been looking at Raman designs, and they all seem to have beam splitters in them. but I don't see one in your design. I have never been really sure why there was a beam splitter in the first place, so perhaps it isn't needed, but I don't understand why anyone would reduce the amplitude of the reflected light by a factor of 2 if it were not needed.  Additionally, Is more lines better or worse? (I can get a good 2500 lines per mm for $26).

  Are you sure? yes | no

David H Haffner Sr wrote 01/13/2017 at 19:56 point

Hey David, first, the more lines per mm the higher the spectral resolution, but will "reduce" your wavelength range, so when choosing a higher order grating you have to make sure you know what wavelength your working in.

1200 lines is perfect when using Holographic gratings or high quality ruled blaze angled gratings, the DVD piece is fine at 1540 lines, mostly because some of those lines are not placed so perfect during manufacturing, but there are enough good lines that are parallel where the diffractive properties are just fine, (hence the Schott glass color filter.)

Second, beam splitters, especially the cube type, are used to separate wavelength and power distribution of the laser's collimated light, in the case of Raman spectroscopy, it is used because in most set ups, there is an adjustable diffraction grating that can be rotated to select a particular wavelength. 

I don't have to use it, although it certainly would improve the overall sensitivity of my system but then it will start to become very complex and costly and since I am only concerned with the region between 500-4000 cm -1 (546.5 - 675.6nm,) I am confident all will be well. 

I know it may seem a bit strange why you would want to attenuate the incoming light beam, but depending on the application, you may want to only have 45% transmission 55% reflectance or aligned for maximum p-polarized transmission (99% reflected - 1% transmitted.) 



  Are you sure? yes | no

David H Haffner Sr wrote 01/13/2017 at 20:05 point

Also I wanted to add a quick note, mine has a secret weapon; 532nm, 12.5mm Diameter, Raman Edge Filter. http://www.edmundoptics.com/optics/optical-filters/longpass-edge-filters/raman-longpass-edge-filters/86225/

  Are you sure? yes | no

Ryan White wrote 01/23/2017 at 11:07 point

There ya go, that's what's up, but you've gotta hold your laser on that wavelength, and your laser needs to be single mode, what's your source?

  Are you sure? yes | no

David H Haffner Sr wrote 01/13/2017 at 08:38 point

Hey Ted, for an application such as this one, I would use a UV Reflective Holographic Grating, 1200/mm. Cost is around $131.00US, depending on the source and quality.

Also I wanted to add that, Holographic gratings have a low occurrence of periodic errors, which results in limited ghosting, unlike ruled gratings. The low stray light of these gratings makes them ideal for applications where the signal-to-noise ratio is critical, such as Raman Spectroscopy.

I am hoping that the Schott glass color filter placement with the diffraction grading placed before the spectral image strikes the detector, will eliminate the stray light and most ghosting effects, if not, I will be forced to adapt and use the holographic grading, which will cause a slight re-design and significant up-cost.

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David Challener wrote 01/12/2017 at 22:56 point

So next question - why are you using a DVD for your diffraction grating?  I see them used in very low cost spectrometers, but they clearly aren't quite parallel lines.  Does this matter?

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David H Haffner Sr wrote 01/12/2017 at 23:53 point

Hey David, good question, I'm using the 4.7G DVD piece with 1540 lines per mm. Spectral resolution is more important than how straight the lines may be on the diffraction grating, I've been researching this aspect for over a year now and I know that it does work, you just have to be willing to be patient and rotate the grating carefully until the spectral lines are straight.

I explained how to do this in a previous log and in some research notes on Public Lab. That is also why I cut the piece 18 x 18mm square and placed each corner on the flat top end of the Schott glass filter locking sleeve, so it can be rotated as you are watching the spectral lines in live capture mode on screen. 

I use a 2300K 13W CFL (compact fluorescent light) to calibrate the diffraction grating piece because of the mercury lines.

I hope this explanation helped!



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David Challener wrote 01/11/2017 at 17:14 point

I am interested in building one of these.   Is it ready to go?

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David H Haffner Sr wrote 01/11/2017 at 17:29 point

Hey David, everything is ready except the Raman longpass edge filter, I will not be able to purchase it until sometime next month, I included it on the bill of materials because it certainly needs to be there.

The rest of the device is performing beautiful in the UV/VIS range-300-800nm. It will do absorption/fluorescence and UV as it stands at this moment.

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PointyOintment wrote 01/10/2017 at 09:22 point

> The DAV5 V3 Spectrometer will be the only project build here on Hackaday in its category

Even if the category is as narrow as "open-source 3D-printed Raman spectrometers", there's already another project in it: #ramanPi - Raman Spectrometer

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David H Haffner Sr wrote 01/10/2017 at 11:38 point

Hey pointyointment, yes that is true, but the Ramanpi project's main documentation is mainly centered around the 3D printing of their design and on their concept of home automation. Proving their concept is very questionable for such bold claims.

They do not have sufficient scientific documentation validating the Raman aspects of their device. The process for doing so is very meticulous and precise and must be done with caution, scientific claims must be able to stand up to intense scientific scrutiny by your peer community and not be prefaced by popularity.

My project has intentional and methodical steps and protocols in order for clear validation, when I am ready to capture Raman signals that will be a whole separate set of steps and protocols.

Also, my project includes cost analysis for full transparency, in order to keep the projects main goal under $700.00US. The average cost even for a 3D printed version of high sensitivity and precision can cost upwards of $2500.00 to 3000.00US Total.

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Ted Yapo wrote 01/13/2017 at 00:35 point

Do you know approximately how much cost it would add to the BOM to use a commercial replica grating instead?

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fl@C@ wrote 03/09/2017 at 11:00 point

I would have hoped that you would have contributed to, instead of insulting a project that clearly inspired not only the name of this project, but the design as well..  Although, after reading your replies to most of the comments here.....It doesn't sound likely that your input would be very useful when taken as a member of a group, rather than you taking credit and imposing your superior knowledge on everyone.  If your understanding of ramanPi is limited to the thought that it is centered around home automation, maybe you should review the documentation again.  It's quite interesting that you seem to have chosen many of the same components, for such a questionable concept... 

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Jarral Ryter wrote 01/05/2017 at 21:28 point

yes raman has some sort of light scattering by shining laser onto the sample.... maybe you made a fluorescence spectrometer. Which is still cool.

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David H Haffner Sr wrote 11/24/2016 at 14:47 point

Hey Ryan, that's a good question, and I'm glad you asked it. Most Raman spectrometers are usually quite large and have very complicated optical designs, but the basic operating principle is still the same, resolving power of the optical mirrors and lines per mm on the diffraction grating.

A raman spectrometer can be composed of either a CCD or a CMOS detector, I have worked for a year researching the cmos type, and that is why I am using it, (cmos,) I am experimenting with the use of only one mirror, the square silver coated focusing one. The optical resolution of the spectrometer is determined by the input slit size and the optics inside the spectrometer. The best possible resolution that can be obtained is the diffraction limit, which is the resolution obtained with an infinitely small input slit. The diffraction limit is related to the size of the beam width inside the spectrometer.

The wider the beam, the more grating lines the beam illuminates and, therefore, the better the resolution. This is also referred to as the resolving power of the grating.

I will be posting a more detailed explanation of the theory and concept of my design, and the mathematics to back it up, plus I have research to back up this design also. So Raman merely means the resolving power of the spectrometer to clearly define the spectral lines with precise definition for accurate molecular finger printing.

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Ryan White wrote 01/23/2017 at 11:03 point

OK, but, Raman spectrometers use high intensity laser sources and look for the signature in the Raman shift of the scattered light, right? So basically you're looking for very weak signals very close to, but not at, the wavelength of the light source. 

Raman spectrometers use laser sources of very high spectral purity (i.e. narrow spectral line width, low phase noise, whatever you want to call it) and very narrow band filters, and as far as I understand it both are tunable, you don't seem to have either. "modern instrumentation almost universally employs notch or edge filters for laser rejection and spectrographs either axial transmissive (AT), Czerny–Turner (CT) monochromator, or FT (Fourier transform spectroscopy based), and CCD detectors." - https://en.wikipedia.org/wiki/Raman_spectroscopy

This, as far as I can tell, is not a Raman spectrometer.

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Ryan White wrote 01/23/2017 at 11:05 point

I've just seen your more recent comments, I'd love to see this working and I'd love to see how you're controlling the wavelength of the laser source. 

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David H Haffner Sr wrote 01/23/2017 at 11:43 point

Ok Ryan, my laser is a CW (continuous wave,) 150mW DPSS, I have posted the specifications for it here many times, I have a 532nm CWL, 10nm FWHM, 25mm bandpass filter employed in my fiber optic laser collimation tube assembly, I have already stated in previous postings that I am waiting on my 532nm, 12.5mm Diameter, Raman Edge Filter, it costs $450.00US, I am not made of $$.

I never stated it was a Raman spectrometer YET, it will be by the time I am finished, I strive for perfection, not speed or popularity. I do NOT need a CCD to detect Raman signals.

Finally, I am not going to explain myself over and over again, when I have been quite clear in my research and documentation, not only about Raman spectroscopy, but spectroscopy and chemistry itself. Read my work.

 

  

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Ryan White wrote 01/23/2017 at 11:48 point

Good luck with it! I'm watching with interest because I know how hard this stuff is, not because I think you won't do it. The internet is bad at capturing my tone, and (as I'm sure you know) there's been a lot of bullshit merchantry around handheld raman spectrometers for all kinds of applications, hence my skepticism. 

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Ryan White wrote 01/23/2017 at 11:52 point

Nice write-ups as well, looking forward to seeing the results (and building one!) 

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Ryan White wrote 11/24/2016 at 13:37 point

How is this Raman? 

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