Multiple polarizers experimental apparatus - Revision history

Ist12916: /* Optical path calibration */

2026-06-02T09:55:23Z

Optical path calibration

Ist1106345: fixed index of software

2026-05-26T23:35:08Z

fixed index of software

Ist1106345: updated software+firmware sections (Laranjo)

2026-05-26T23:23:59Z

updated software+firmware sections (Laranjo)

Show changes

Ist193156 at 19:29, 26 August 2025

2025-08-26T19:29:19Z

Ist193156 at 19:26, 26 August 2025

2025-08-26T19:26:46Z

Ist193156 at 19:24, 26 August 2025

2025-08-26T19:24:43Z

Ist193156: /* Order of assembly */

2025-07-18T13:17:24Z

Order of assembly

Ist193156: /* Order of assembly */

2025-07-18T11:51:43Z

Order of assembly

Ist1102577: /* Software */

2025-06-12T15:13:13Z

Software

Ist1102577: /* Electronic component assembly */

2025-06-12T15:07:08Z

Electronic component assembly

@@ Line 454: / Line 454: @@
 The first polarizer is fixed and shall be positioned with a couple of degrees in order to avoid starting the experiment from a maximum, allowing for easy observation of such maxima. Consider having it around ~15º to 30º and well secured, eventually with glue.
-Then start the calibration procedure by inserting the second polarizer and rotating it until the maximums are detected and measured (usually two). Take note of their value and leave the second polarizer at rest in the measured position. Now insert the third polarizer and repeat the procedure for the detection of the maximums and do this for the rest of them.
+Then start the calibration procedure of the second polarizer by rotating in block all the remaining polarizers and detect the maximum intensity and register it. Leave the second polarizer at rest in the measured maximum position. Now rotate again the remain block of polarizer simultaneously, and repeat the procedure for the detection of the maximums for the rest of them. Take note of all maximum values and publish them.
 Every time a hard film or lens is installed it has to be firmly fixed or glued. If glue is used it ''must not damage the polarizer film''.

@@ Line 462: / Line 462: @@
 Later, when performing the experiments these values of offsets must be considered in order to eliminate the systematic error of the system.
-== Software ==
 To properly use the experiment, commands and data retrieval have to be in place. This can be achieved in two ways acting through the serial connection to the Arduino Mega.

@@ Line 330: / Line 330: @@
 {|
 |[[File:stepper_wires_placement.jpg|thumb|Wires connection in the RAMPS 1.4.]]
-|[[File:switches_wires_placement_software.png|thumb|Wires and switches connection in the RAMPS 1.4 (software view) according to each step-motor.]]
+|[[File:stepper_array.png|thumb|Top-view of kit:numbering of thre steppers and respective switches.]]
 |[[File:switches_wires_placement_software.png|thumb|Switches' wires (green) and step-motor wires (blue) (software view).]]
 |}

@@ Line 330: / Line 330: @@
 {|
 |[[File:stepper_wires_placement.jpg|thumb|Wires connection in the RAMPS 1.4.]]
-|[[File:stepper_array.png|thumb|Wires and switches connection in the RAMPS 1.4 (software view) according to each step-motor.]]
+|[[File:switches_wires_placement_software.png|thumb|Wires and switches connection in the RAMPS 1.4 (software view) according to each step-motor.]]
 |[[File:switches_wires_placement_software.png|thumb|Switches' wires (green) and step-motor wires (blue) (software view).]]
 |}

@@ Line 330: / Line 330: @@
 {|
 |[[File:stepper_wires_placement.jpg|thumb|Wires connection in the RAMPS 1.4.]]
-|[[File:stepper_wires_placement_software.png|thumb|Wires and switches connection in the RAMPS 1.4 (software view) according to each step-motor.]]
+|[[File:stepper_array.png|thumb|Wires and switches connection in the RAMPS 1.4 (software view) according to each step-motor.]]
 |[[File:switches_wires_placement_software.png|thumb|Switches' wires (green) and step-motor wires (blue) (software view).]]
 |}

@@ Line 67: / Line 67: @@
 | Bar || Support bar for polarizer supports; adjusts compression exerted || Polarizer Assembly || 1 || PLA || No
 |-
-| Roda dentada || Gear wheel that fits behind each polarizer || Polarizer Assembly || 5 || PLA || No
+| Gear || Gear wheel that fits behind each polarizer || Polarizer Assembly || 5 || PLA || No
 |-
-| Fixed Polarizer Holder || Fixed polarizer holder that fits into the polarizer detector holder || Optical Assembly || 1 || PLA || No
+| Fixed Polarizer Holder || Fixed polarizer holder that fits into the polarizer Support led || Optical Assembly || 1 || PLA || yes
 |-
-| Detector Holder || Part that holds the LED holder || Optical Assembly || 1 || PLA || No
+| Detector Holder || Part that secures the LED adjuster || Optical Assembly || 1 || PLA || No
 |-
-| Detector Adjuster || Part that holds the LED holder || Optical Assembly || 1 || PLA || No
+| Detector Adjuster || Part that secures the LED holder || Optical Assembly || 1 || PLA || No
 |-
 | Led Holder || LED and detector holder, which fits into the adjustment parts above || Optical Assembly || 2 || PLA || No
 |}
 . Peel the supports of the pulleys using pliers or an X-Acto knife.

@@ Line 23: / Line 23: @@
 |[[File:parts_needed_.png|thumb|x400px|Top|Parts needed for the assembly]]
 |}
+The following table can be used to check the number of parts to be printed and if supports are needed:
 . Peel the supports of the pulleys using pliers or an X-Acto knife.
 {|

@@ Line 401: / Line 401: @@
 =Software =
-To properly use the experiment, commands and data retrieval has to be in place. This can be achieved by two ways acting through the serial connection to the Arduino Mega.
+To properly use the experiment, commands and data retrieval have to be in place. This can be achieved in two ways acting through the serial connection to the Arduino Mega.
-The firmware existing in the Arduido is able to (i) configure the experiment (ii) run and retrieve the generated data and (iii) execute some specialized function in order to test, calibrate and maintain the experiment. To interface with the firmware it can be use (i) a python proxy code (high level software layer) capable to interoperate with the FREE server or a (ii) a terminal emulator like Minicom avaiable for Linux that allows you to send and receive data over the serial connection.
+The firmware existing in the Arduido is able to (i) configure the experiment (ii) run and retrieve the generated data and (iii) execute some specialized function in order to test, calibrate and maintain the experiment. To interface with the firmware it can be used (i) a python proxy code (high-level software layer) capable of interoperating with the FREE server or (ii) a terminal emulator like Minicom available for Linux that allows you to send and receive data over the serial connection.
 ==Raspberry FREE proxy==
-The Raspberry Pi is responsible for transmitting the video feed of the experiment and establishing communication with the FREE-Server by using a proxy interface. The FREE hosts the graphical user interface (GUI) to the clients. This section provides a concise overview of the procedure used to control all electronic components via the arduino, as well as the communication protocols between the arduino and the FREE-Server.
+The Raspberry Pi is responsible for transmitting the video feed of the experiment and establishing communication with the FREE-Server by using a proxy interface. The FREE hosts the graphical user interface (GUI) to the clients. This section provides a concise overview of the procedure used to control all electronic components via the Arduino, as well as the communication protocols between the Arduino and the FREE-Server.
 ===Communication model between the FREE-Server and the Raspberry PI===
-The communication between the server and the experiment follows the elab’s structured protocol that enables real-time interaction and data exchange. The central server, Exp Server, acts as an intermediary between users and the experimental apparatus (RPi Server). Users interact with Exp Server via a web interface made with Django, a high-level Python web framework, to configure and control the experiment parameters, while Exp Server which directly relays these commands to the experimental setup. The communication between Exp Server and RPi Server occurs over the internet using JSON-formatted messages, ensuring flexibility across different experimental configurations. Authentication is
+The communication between the server and the experiment follows the elab’s structured protocol that enables real-time interaction and data exchange. The central server, Exp Server, acts as an intermediary between users and the experimental apparatus (RPi Server). Users interact with Exp Server via a web interface made with Django, a high-level Python web framework, to configure and control the experiment parameters, while Exp Server directly relays these commands to the experimental setup. The communication between Exp Server and RPi Server occurs over the internet using JSON-formatted messages, ensuring flexibility across different experimental configurations. Authentication is performed at the connection stage, where the RPi Server transmits an ID and a secret key for verification. Once authenticated, the Exp Server sends an experiment-specific configuration file to the RPi Server, which then establishes communication with the local controller using the predefined protocol [7]. Throughout the experiment, the RPi Server continuously exchanges status updates, experimental results, and error messages with the XP server, ensuring synchronized operation and real-time data accessibility for users.
 ===Communication model between the Raspberry PI and the Arduino Mega===
@@ Line 421: / Line 420: @@
 Fig. 11: ReC Generic Drive State-machine diagram of the driver [7]
-By reading the arduino’s serial port at a baud rate of 115200 bits per second, the user sends a bit string (ending with the character ’\r’). The configuration message is defined as:
+By reading the Arduino’s serial port at a baud rate of 115200 bits per second, the user sends a bit string (ending with the character ’\r’). The configuration message is defined as:
   cfg p0 p1 p2 p3 p4 p5 p6 p7\r
-where p0 defines the state of LED (on or off), p1 p2 p3 p4 and p5 define the angle (in steps of 0.36◦) at which the experiment will start the sweep, p6 defines what polarizer will be sweeping
+Where p0 defines the state of the LED (on or off), p1 p2 p3 p4 and p5 define the angle (in steps of 0.36◦) at which the experiment will start the sweep, p6 defines what polarizer will be sweeping (if does not pretend to sweep then p6 is 0) and p7 defines the limit angle of the polarizer being swept (also in steps of 0.36◦) at which the experiment will stop.
 ==Firmware==
@@ Line 434: / Line 432: @@
 To execute a discrete sequence of steps based on a given angle in degrees, the rotate function was implemented. The motor rotates to the low nearest integer multiple of 1.8◦ to the provided angle.
-The data acquisition interval is crucial for the final experiment since the goal is to optimize the user experience by minimizing waiting times when retrieving intensity of light and scanning angle data. To address this, a global RPM of 600 revolutions per minute was used. With a scanning limit of 324◦ (as previously mentioned in Section III), the experimentally measured data acquisition time for scanning one or more polarizers simultaneously was approximately 40 seconds.
+The data acquisition interval is crucial for the final experiment since the goal is to optimize the user experience by minimizing waiting times when retrieving the intensity of light and scanning angle data. To address this, a global RPM of 600 revolutions per minute was used. With a scanning limit of 324◦ (as previously mentioned in Section III), the experimentally measured data acquisition time for scanning one or more polarizers simultaneously was approximately 40 seconds.
-To further refine the voltage readings from the photodiode, an arithmetic mean of N points was implemented in the photodiode voltage reading function. By computing the arithmetic mean over 13 points of the value being measured, the standard deviation of this mean reduces the original standard deviation in ≈ 27.14%. This reduction was deemed acceptable for the experiment, as the data adjustment performed was successful, as will be observed in Section V).
+To further refine the voltage readings from the photodiode, an arithmetic mean of N points was implemented in the photodiode voltage reading function. By computing the arithmetic mean over 13 points of the value being measured, the standard deviation of this mean reduces the original standard deviation by ≈ 27.14%. This reduction was deemed acceptable for the experiment, as the data adjustment performed was successful, as will be observed in Section V).
 =Links=

@@ Line 276: / Line 276: @@
 |}
-. Place the electric circuit in the box corner, positioning it accordingly to the holes, and bolt it.
+. Place the electric circuit in the box corner, position it according to the holes, and bolt it.
 {|
 |[[File:electric_circuit.jpg|thumb|Switchers positioning in the switch holder.]]