xSpectrolum version v0.71
Version 0.71 of the xSpectrolum series is built using the Arduino NANO IOT 33 board. Compared to version 0.06, version 0.71 uses the Hamamatsu C12880MA sensor without any breakout board. Additionally, the aviation plug is upgraded to a 6-pin version, to allow for 4 digital channels from an RS-485 MODBUS breakout board (note that the RS-485 breakout board is enclosed with the external sensor and not part of the wiring here). As with model versions 0.03 through 0.06, additional light sources are built into attachments and directly powered from the battery via a metal–oxide–semiconductor field-effect transistor (MOSFET).
Note that version 0.71 is not intended for production, but is built as a template for designing and testing the wiring of a purpose built shield or Printed Circuit Borad (PCB) to be fitted with an arduino type microcontroller. Not necessarily the Ardiono NANO IOT 33 board.
The step from wiring a set of breakout boards to a shield or PCB designates a major development; hence the step from 0.06 to 0.7.
Light emission sources
One of the major shortcomings with the solution of all versions from 0.03 is the power supply for the electromagnetic emitter. The voltage and current supplied from the spectrometer to the muzzle with the light source depends on the charge level of the battery, and is regulated by a simple resistor in the muzzle unit. As the battery potential can vary between around 3 volt (low charge) to 4.2 volt (fully charged) the emitter is not generating a constant field. Further the resistor is a poor solution that wastes battery power, does not adjust for the potential and generates heat. A new solution is needed, and for that purpose the light sources to be used with forthcoming versions are listed here and summarised in table 1:
- xenon bulb, 3.0 V, 300 mA
- IR broad band emitter (LED), 2.25 - 3.0 V, max 500 mA
- Neutral white led, 2.75 V, 65 - 200 mA(?)
- Alt. neutral white led, 3.0 V, 60 mA
- Blue laser, 4.8-5.6 V, 35 - 60 mA
- Green laser, 5.0 V, 45 mA
- red laser, 2.2-2.4 V, 20 mA
- UV led, 3.5 V, 20 mA
- Standard LEDs @ 3 - 3.3 V and 20 mA (in different wavelengths)
Table 1. Emission sources for the xSpectre spectrometer.
source | type | min potential | max potential | min current | max current | connection |
- | - | V | V | mA | mA | - |
Xenon | VIS+NIR | 1.6 | 3.0 | 200 | 300 | Bi-Pin 1.27 mm |
IR led | VIS+NIR | 2.25 | 3.0 | 300 | 500 | surface mount |
White LED 1 | VIS | 2.75 | 2.75 | 65 | 200 | surface mount |
White LED 2 | VIS | 3.0 | 3.0 | 60 | 120 | surface mount |
Blue | laser | 4.8 | 5.6 | 35 | 60 | 3-pin TO-18 |
Green | laser | 5.0 | 6.6 | 45 | 75 | 3-pin TO-18 |
Red | laser | 2.2 | 2.5 | 20 | 22 | 3-pin TO-18 |
UV led | monochrom | 3.2 | 3.5 | 20 | 20 | catod/anod |
Blue led | monochrom | 3.3 | 3.3 | 20 | 20 | catod/anod |
Green led | monochrom | 2.5 | 3.5 | 10 | 20 | catod/anod |
Except for the xenon and IR broad band emitter, other altrnatives are available.
To cover the spectral range of interest, both with broadband emitters as well as single wavelength LED and laser emitters, at least 3 different forward current solutions are presumably required:
- 3.3 V and 20 mA for any standard 2-pin (cathode/anode) LED emitters and red lasers, whether broadband or single wavelength,
- 5.0 V and 45 mA for short wave (blue to green) laser diodes,
- 3.0 V and 300 mA for xenon, IR broad band emitter and neutral white LED emitters.
Version 0.71 contains a battery and breakout boards controlling the charging and drainage of the battery, a fixed DC to DC stepup module outputting 5 volt, and a power switch. All included modules/components are listed below.
pin | symbol | id | I/O | comment |
1 | +Vs | Vin | I | 5 V input |
2 | GND | Ground | - | Ground |
3 | +Vs | Vin | I | 5 V input |
4 | CLK | Clock pulse | I | Sensor clock pulse |
5 | Case | Case | - | Case connection |
6 | ST | Start pulse | I | Sensor start pulse |
7 | TRG | Trigger pulse | O | Pulse for signals |
8 | - | Fastening | - | Do not connect! |
9 | EOS | End Of Scan | O | Sensor scan end |
10 | Video | Video output | O | Sensor video output |
Spectrometer box
The container holding all the components is larger than earlier versions, approximately 95 x 55 mm. The openings at the far end is for the external probes.
The spectrometer box (.stl) for 3D printing is available as spectro-box-HAMA-VIS_20210831_v071a.stl.
Spectrometer sample and light source attachments
The sample attachments for version 0.71 includes the required light sources. The samplers are attached to the spectrometer container using TRX connections. The light, samples and spectral sensor are thus always lined up in the most optimal manner regarding each sample type and light source.
Direct sampling probe
The muzzle attachments containing the emitters and holding the samples, are the same as for v0.6x:
- white LED light (VIS sensing)
- xenon light (VIS-NIR sensing)
- blue LED (VIS-NIR fluorescence)
- red/green laser (NIR Raman spectroscopy)
Application of the red or green laser Raman spectroscopy requires a controlled (indoor) environment with no or little ambient light condition.
Controlled solid sampler
The controlled grind (solid) muzzles resemble the direct muzzles, but with a longer cylinder and a sample holder that fits into the lower half of the cylinder. This gives a more controlled light environment compared to direct sampler. Additionally the use of reference reflectance samples can be used for instrument calibration in direct association with the sensing. The controlled soil sampler thus comes in the same four (4) versions as the solid sampler:
- white light (VIS sensing)
- xenon light (VIS-NIR sensing)
- blue led (VIS-NIR fluorescence)
- red/green laser (NIR Raman spectroscopy)
Cuvette sampler
All cuvette samplers are built from two pieces, the cuvette holder, and the foundation that attach to the spectrometer container. The foundation is the same for all cuvette holders. The cuvette holder comes in 5 versions:
- white LED front light (VIS sensing of opaque liquids)
- white LED back light (VIS sensing of transparent liquids)
- xenon back light (VIS-NIR sensing of transparent liquids)
- blue led side light (VIS-NIR fluorescence of transparent liquids)
- green laser side light (VIS-NIR Raman spectroscopy of transparent liquids)
- red laser side light (NIR Raman spectroscopy of transparent liquids)
Modules, components and sensors
xSpectrolum v0.71 is constructed from set of modules and components, and can also attach external sensors using either an aviator plug or a BNC prot. To get more information on these modules, components and sensors, including the separate scripts for individual controls, follow the links below.
GX aviator plug GX12/GX16 aviator plug pH meter - DFRobot ph meter DFRobot for 5 volt TRX connection TRX power connector Xenon light with MOSFET regulation Xenon light with MOSFET regulation OSRAM IR led OSRAM broadband IR light for spectrometers FQP30N06L MOSFET FQP30N06L MOSFET transistor for switching power on/off On-off switch Single pole gliding power switch Hamamatsu C12880MA spectrometer Hamamatsu C12880MA miniaturised visible, 288 band sensor Arduino NANO IOT 33 Arduino NANO IOT 33 microcontroller board SHT10 moisture and temperature sensor SHTXY moisture and temperature sensor Capacitive Soil Moisture Sensor v1.2 Capacitive Soil Moisture Sensor v1.2 Sparkfun AS7263 6-Channel infrared spectrometer Sparkfun Breakout board with AMS AS7263 infrared spectrometer Adafruit AS7262 6-Channel Visible spectrometer Adafruit Breakout board with AMS AS7262 spectrometer