Spring 2018 3DoT Hexy: UV Sensors Study

April 15, 2018/in 3Dot Spiderbot Generation #2, Spiderbot/by Eduardo De La Cruz

By: Kris Osuna (Electronics & Control Engineer)

Verified by: Eduardo De La Cruz (Project Manager and Manufacturing Engineer)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Introduction

The original idea for the autonomous navigation of the maze was to have 3DoT Hexy take a picture, process the image and decide its action based on the image. The camera idea was proven to be too extensive with a high learning curve, so we are researched other methods for the autonomous part of the maze. We have decided to look into UV sensors to detect and follow a UV marker line.

Requirements

Must detect the presence of the UV marker line
Must be able to differentiate between UV marker line and no UV marker line

Materials

Update 4 (April 19, 2018)

We are no longer using 5V to drive the LEDs. We changed UV LEDs to IR LEDs since the data shows that the UV sensors can not accurately differentiate when the UV LEDs are powered by 3.3V.

Update 3 (April 1, 2018)

Some samples were obtained that should have UV ink. In a similar way as Update 2, data was measured at different spots on the samples.

Data

Table 1: UV light test under different UV ink surfaces

Samples containing UV ink data.

All samples were taken with UV LEDs at 5V. It did not look like there was much UV print on the skyscraper sample. The light post seemed to have the most UV ink, because of how it illuminates under UV light. The data shows that the values for the lamp post are lower than the values for the light blue sky. The dark skyscraper has lower values than the lamp post, so the sensor can tell the difference between dark and light. The overall trend in all the data is that the UV sensor is working more like a color sensor. This is somewhat expected since lighter colors reflect more light. We expected the UV marker or UV ink to have a bigger impact on the reflection, but it did not. This might be due to the UV ink and UV marker not being the right wavelength for the sensor to pick up. The maze can be made with white and black lines. However, this would be the same as the current maze that is used. We are currently looking at other options.

Update 2 (March 13, 2018)

Performing a field of view test

Figure 1: New set-up for measuring values

405 nm LED used at a 25° angle, .7 inch away and .3 inch vertically as seen in figure 1. The calibrated light sensor is 1 inch above the marked line pointing straight down. Two UV LEDs were used at the beginning, but one stopped working. A pack of one hundred 395 nm UV LEDs were ordered to redo the testing with multiple LED testing. Measurements were taken at the center of the UV marked line, at the edge of the marked line then measurements at every half an inch away from the edge until 2 inches away from the edge of the line.

Data

Table 2: UV test results

Link to the new measurements

Conclusion

The data shows that the UV sensor values, when the UV LEDs are driven at 3.3V, is not reliable for detection. The value differences on all materials is very small making detection very difficult. The best values I obtained were on white plastic. The values show that the UV index with a threshold of .06 would best be used. This has a nice drop off that could be used to make the maze.

Update 1 (March 6, 2018)

Test 1

The UV sensors we looked at were the Si1145/46/47 and the SL1145. Once the sensor was received testing was begun immediately. First tests should that the UV marker was not being detected by the UV sensor. Closer reading of the Si1145/46/47 datasheet revealed that the UV reading is not a “true” UV reading. The sensor uses a calibrated light-sensor to find the UV index.

We decided to find a true UV sensor. The sensor we used is the GUVA-S12SD which is an analog “true” UV sensor that reads that detects 240-370 nm wavelengths. The sensor works with voltages of 2.5-5.5V which is within our robot’s range. When the GUVA-S12SD sensor arrived we hit a roadblock. The sensor would not get a reading even with a UV blacklight directly on the sensor. We believe that the UV marker does not give out a wavelength that the sensor can reach. We used a black light to illuminate the UV line and the GUVA-S12SD did not receive any information. We believe this is because the UV marker is not in the 240-370 nm range.

We went back to the Si1145/46/47 with a blacklight directly on top. This gave us a UV index readout. We were able to reverse engineer how they obtain UV index from wavelengths. Our UV index value was multiplied by a constant of 25 then multiplied by 100 to make the value easier to read. The test was performed at two different values 3.3 V and 5 V: 3.3 v is the minimum voltage obtained from a pin read out when we used a multi-meter and 5 V is the voltage if we were to use a booster shield. Blacklight was 1 inch away straight above and tested on a 1 x 1 inch square that was marked by the UV marker. Measuring was started on the UV line and moved out of the UV marked square. Plastic white at 1 inch away seems to give the best results.

UV Light directly on the UV sensor 1500-2300*

*Cloth was Grey 90% Cotton 10% Polyester

Table 3: .5-inch distance results

Table 4: 1-inch distance results

Table 5: 2-inch distance results

Figure 2: Flora UV index sensor – Si1145 light sensor

Figure 3: Analog UV sensor

Figure 4: UV marker

Figure 5: Measuring set-up

Resources

AT-ST Verification Test Plan

April 15, 2018/in 3Dot AT-ST/by Intiser Kabir

By: Joseph Cho (Mission, Systems, and Testing)

Verified By: Intiser Kabir (Project Manager)

Approved By: Miguel Garcia (Quality Assurance)

Table of Contents

Introduction

Verification test plan is used to verify our L1 and L2 requirements through analysis, inspection, demonstration, and/or testing. The L1 and L2 requirements are listed in the spreadsheet below. The test plans will be generated from the spreadsheet. Few of L1 and L2 requirements have been reworded by MST.

Please be noted:

GL1 is General Level 1 requirement;

SL1 is Specific Level 1 requirement;

SL2 is Specific Level 2 requirement.

Verification Matrix

Figure 1: Verification Matrix

Figure 2: Verification Matrix continued.

Figure 3: Verification Matrix continued.Description:

This matrix contains all of the verification needed for the AT-ST. Each test cases are differently colored. Test Case 1 is green, Test Case 2 is blue, Test Case 3 is yellow, and Test Case 4 is red.

Test Cases

TC-01: General Inspection

Description: Verify all of AT-ST inspections..

Test Environment: Indoors on a level surface. Preferred to be inside ECS 316.

Figure 4: Test Case 1 (included in the Verification matrix)

Figure 5: Test Case 1 Continued

Figure 6: Test Case 1 Continued

Figure 7: Test Case 1 Procedure Step

TC-02: Maze Demonstration

Description: Verify all requirements for the hedge maze.

Test Environment: Indoors on a level surface. Preferred to be inside ECS 316.

Figure 8: Test Case 2

Figure 9: Test Case 2 Continued

Figure 10: Test Case 2 Procedure Step

TC-03: ArxTerra App. Demonstration

Description: Verify all requirements for ArxTerra App. Demonstration

Test Environment: Indoors on a level surface. Preferred to be inside ECS 316.

Figure 11: Test Case 3

Figure 12: Test Case 3 Procedure Step

TC-04: Mechanical Testing

Description: Test all mechanical requirements of AT-ST

Test Environment: Indoors on a level surface. Preferred to be inside ECS 316.

Figure 13: Test Case 4

Figure 14: Test Case 4 Procedure Step

Description

The test cases above is a list of test cases that will be done in order to test the level one and level two requirements of AT-ST. All these tests will be done as the project progresses and additional test cases may be added in the near future.

References

Goliath Fall 2017 Verification and validation test plans:

https://docs.google.com/document/d/1AxqEOK9IbOjYYHCB_hjBvkPCMkmBkUHTAropGCucphM/edit?usp=sharing

Goliath Verification and validation matrix:

https://docs.google.com/spreadsheets/d/1nidxLcOYEpPlr_o6vkksaHdT84JXj-LlkuektFs7Hwg/edit?usp=sharing

AT-ST Verification and validation matrix:

https://docs.google.com/spreadsheets/d/1HHaQliwvLYbqErqJi2AVOlqGEzNX7grKOYJ2CBUFQ7M/edit?usp=sharing

AT-ST L1 and L2 requirements:

www.arxterra.com/spring-2018-at-st-project-specific-requirements-and-objective-l1l2/

Spring 2018 3DoT Hexy: Power Estimate of Micro Metals

April 13, 2018/in 3Dot Spiderbot Generation #2, Spiderbot/by Eduardo De La Cruz

By: Kris Osuna (Electronics & Control Engineer)

Verified by: Eduardo De La Cruz (Project Manager and Manufacturing Engineer)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Introduction

We obtained two unidentifiable DC motors from Professor Hill’s resource cabinets. Current and Voltage measurements were obtained using an Arduino Uno and INA3221 Breakout Board. Measurements were taken with a load that is half the weight of 3DoT, 66.3g, and the gears in motion. We purchased two DFRobot FIT0481 micro metal gear motors and began our testing.

Components Needed

Scale
3DoT David
3 micro metal gear motors
INA3221 breakout board
Arduino Uno
Opto-Reflective switch
2 NPN transistors
Resistors 100, 200, 1k
Process Control Student Guide by Parallax INC

Related Requirements

The micro metal motor must be able to turn six gears
The motor must be able to work in the 3.7-5V range
The motor must have an RPM of at least 360 with a 66.3g load

Setup

A riser was placed on the scale and tared so that we can weigh 3DoT David shown in figure 1. 3DoT David weighs 132.6 grams. There are two micro metal motors used so each motor will have a load of 66.3 g. The original motor inside 3DoT David was removed. The motors were connected to the INA3221 breakout board to measure current with no load. Set up can be seen in figure 2. RPM was calculated by using the opto-reflective switch to read the black marked paper on the sheet attached to the motor shown in figure 3. The motor spins the attached piece of paper, which is half black and half white. The opto-reflective switch has an IR LED and phototransistor which is able to differentiate the black and white part of the paper. Each count means a full rotation was achieved. The motor shaft was marked black and recorded for 10 seconds then played in slow motion to confirm that the opto-reflective switch readings were correct.

The motor being tested replaced the motor inside 3DoT David. This is done so that the gears moving would be part of the load. The motors are connected to the INA3221 breakout board to measure the current while dealing with the load. RPM was calculated by using the opto-reflective switch to read the black on the sheet taped to the gear attached to the motor. The gear attached to the motor was marked, recorded for 10 seconds and watched in slow motion to confirm the opto-reflective results were accurate.

Figure 1: 3DoT David Weight

Figure 2: Current Measurement

Figure 3: Calculating RPM

Figure 4: Full RPM measurement set-up

Figure 5: Current measurement with load

Figure 6: RPM measurement with load

Results

Table 1: Measurements of cabinet motors at 3.7 V

Table 2: Measurement of cabinet motors at 5 V

Table 3: Measurements of our purchase motors

The following graph is for table 3 which uses the purchased micro metals that will be used on 3DoT Hexy

Graph 1: Results from our purchased motors graphed

Analysis

The purchased motors stall at around 3.4 V with a load, because of this it means that we cannot use the 3.3V pins on the Arduino Uno board. The 3DoT board can provide 3.7V to our motors. We are waiting for 3DoT Hexy to be 3D-printed to decide whether we will need 3.7V or 5V power to our motors. Once we find the full weight of 3DoT Hexy with all the sensors attached we should run another power study. The new power study will be more realistic because 3DoT Hexy will be moving and have all the sensors workings. If 3DoT Hexy can take the full load without the motors stalling at 3.7V we would only need one buck booster for the UV LEDs.

Resources

Figure 7: Micro-motors from resource cabinets

Figure 8: Purchased Micro-motor