radiation sensing tank

University of Reykjavik

Final project report

Radiation sensing tank

Author:

Daniel Bergmann Sigtryggsson

Jökull Jóhannsson

Birgir Þór Svavarsson

Instructor:

Joe Foley

November 27, 2011

Abstract

Our project aim was to build a tank robot that could detect radiation and locate it in space.Early we ran into numerous problems in the assembly phase, forcing us to re-scope our projectinto a tank that can drive in space, showing radiation readings on a LCD display. Finally thattask came to a halt when we discovered that all of the pins on the Arduino are all occupiedwhen using only the minimum of 4 data bus pins on the LCD module

We own many thanks to Dr.Andrei Manolescu1 for providing us with both radiation sourcesand radiation sensor board for ARDUINO + geiger tube. We would also want to thank ourinstructor Joe Foley for his support and the lab supervisor Hrannar Traustason for supplyingus with the tank unit, motor-controller, DC motor among other things.

1Physics professor,[RU] School of Science and Engineering, his website can be found in this url:http://www.ru.is/kennarar/manoles/

� Reykjavik University - Fall 2011 - T-411-MECH �

Introduction

Our project aim was to build a tank robot that could detect radiation and locate it in space. Dueto numerous problems that arose in the assembly phase early on, we fell behind on schedule andneeded to re-scope our project to a tank that can drive in space and show a radiation readingon a LCD display module.

In a nutshell this robot is a fair attempt to build a scaled down version of a more sophisti-cated robot currently used in the real world situations.

The problem this project is trying to solve

It is a common knowledge that an exposure to high radiation dosage is unsafe for most livingthings or at least should be avoided by any means. The real reason for the danger according toPrinceton Universities environmental health and safety website[URL11b]is that it does damageto living tissue from the transfer of ionizing energy from the radiations source. MoreoverPrinceton states that these ionizations can be both harmful and not so harmful e.g."producefree radicals, break chemical bonds and even damage molecules that regulate vital cell processes.But the mundane damage from background radiation can easily be repaired. That is not thecase at high doses, cell death results. Causing a tissue failing to function."

The problem to be solved with this project is to make autonomous robot that could bedeployed into a hazardous environment to test if any given space is safe enough for humans tostep into without risking tissue damage or even organ failure.

Who should use it

A possible candidate for a use of a device of this sort could be:

• Anti terrorist units

• Governments

• Military

• Security companies

• Science institutions

Has anyone else done something similar?

After a brief research on the internet one can �nd an obvious example[iRo11] of a similardevice currently on the market is the IROBOT 510 PACKBOTTM2 for HazMat Technicians.The Packbot is lightweight and easily transportable (�ts into a backpack). Amongst itskey features is a sensor that gathers real-time data about gamma radiation and explosive gasesamongst handful of other features. That robot is also capable of complex operations beyondthe scope of this project such as a lever arm with multiple cameras and lights.

2PACKBOT is a registered trademark of iRobot corporation

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Figure 1: Packbot 510 for hazMat[Pac11]. Figure curtesy of iRobot corporation

Our di�ers perhaps mostly on simplicity and cost. However the Packbot price is unavail-able from reliable sources but a cautious estimate could be tens of thousands of dollars. Thusexpanding the market-group range.

Why is this more?

This project could be a much cheaper alternative for a much more complex unit on the market.Also it could turn out a better option in some cases since the robot dimensions are relativelysmall.

Time

Project proposal due date was 26.10.2011, project presentation was scheduled 24.11.2011

Cost

Estimated cost is roughly 30.000 ISK. Fortunately, most of this cost was aided from the goodpeople of the faculty of science and engineering in form of equipment lending. Final expensesfalling on the team came down to the cost of 16 pc.of AA batteries, ARDUINO UNO microcontroller and USB cable. Grand total: 5.000 ISK.

Scope

1. Drive the tank around a given space

2. Sense the radiation levels in the environment

3. Display radiation intensities in Sievert per hour on a LCD module.

4. Stop tank when radiation intensity reaches certain threshold

5. Protective house from plastic since the rays penetrate plastic well.

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Resources

Most of our small resources came form Hrannar's laboratory, that is buttons, wires, tools andetc. We used our own ARDUINO uno microprocessor that we bought earlier this semester.We got a ready to use geiger counter ARDUINO shield from which physics professor AndreiManolescu was kind enough to fund for our project. He got it from the online store CookingHacks by Libelium[Gei11a]The following is list of tools that was used extensively trough out the project assembly.

Tools

• Soldering iron

• Wire cutters and pliers

• hot glue gun

• Screw drivers

The following is list of main equipments chosen for this project.

Equipment

• 2pc. DC motors

• 1pc. Sabertooth 2x5 motorcontroller

• 1pc. Traxter tank robotic kit as seen in �gure 2

• 1pc. Arduino uno prototyping platform as seen in �gure 3

• 1pc. Geiger counter shield for arduino

• 1pc. 2"by6" breadboard

• 2pc. two state buttons

• 8pc. AA batteries

• 1pc. 9v battery

• 15cm2 of plexi glass (2mm thickness)

• Nuts and bolts of various sizes

.

Figure 2: Traxter kit parts[Tra11]

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Figure 3: Arduino uno[?]

DC motors details

Astonishingly, searching the product ID showed no results.[NOr11].Its product ID is: HG37D670WE12-052FH , by Hennkwell. A Taiwanese company that spe-cializes in small gear motors. However, our motors are labelled with some minor speci�cations.

• Operationg voltage: 7.2V

• 160rpm.

• 45-07 � no idea what that number stands for

Our motors has a magnetic encoder that we do not use for this project.

Geiger counter board

According to the Cooking hacks website[Gei11a] the board consists of two primary parts. Thepower circuit is based on an oscillator that connects to a voltage multiplier that composes ofcapacitors, resistors, transistors and diodes (see schematic section for detail). With this circuitwe get the recommended voltage of 350V.

Once powered the tube can generate pulses that is received in the Arduino uno thats countsthem and with easy calculation we can get a more tangible value in Sieverts per hour.

The Arduino counts pulses for 10 seconds, which then gets multiplied by 6 to get pulses perminute(CPM). Then it divides that number by the conversion factor(see speci�cation for ourtube) to obtain SV/h.

The board also have Piezo speaker and LED indicator that sounds and blinks when eachpulse is generated.

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Figure 4: "Geiger board". Curtesy of cookin-hack webstore[Gei11b]

The Geiger tube

The tube that came with the board is from a Chinese company Nordic optics. Its product idis:J305β

Figure 5: "O�cial Geiger tube"[Gei11c], curtesy of Cooking hacks webstore

The Cooking hacks website[Gei11d] has conveniently listed some speci�cations for it, sinceits data sheet is in Chinese. This is the speci�cations:

• Manufacturer: North Optic

• Radiation Detection: β, γ

• Length: 111mm

• Diameter: 11mm

• Recommended Voltage: 350V

• Plateau Voltage: 360-440V

• Sensitivy gamma (60Co): 65cps/(muR/s)

• Sensitivity gamma (equivalent Sievert): 108cpm / (muSv/h)

• Max cpm: 30000

• cps/mR/h: 18

• cpm/m/h: 1080

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• cpm/muSv/h: 123.147092360319

• Factor: 0

Motor-controller

We got the motorcontroller from Hrannars lab. Its product name is Sabertooth 2x5 and itcomes from Dimension Engineering. The data sheet[Sab11] states that the input voltage 6-18V nominal and 20V absolute max. We chose to use 8AA batteries which gave 12V to theSabertooth. Con�guration was done by looking up a convenient mode in the data sheet. Weused the simpli�ed serial mode that uses TTL level single-byte serial commands to set motorspeed and direction. It is a one way transmit from the arduino to S1 on the sabertooth. Thatway it was very convenient because then we could easily manipulate both motors with one 8byte character. Each motor has 7 bit of resolution. We chose 9600 baud rate because that wasrecommended and showed reliable communication.

Figure 6: Sabertooth 2x5[þooth2x5], curtesy of dimension engineering

Power source

Early on we chose to power the motors with 8AA batteries connected in series. We initiallythought that it would be a cheaper and smaller alternative to the rival teams approach of biggerlithium rechargeable batteries. In stead we ended again and again up with empty batteriesmaking it much more expensive. It helped to use quality batteries such as Duracell batteries.To power the Arduino plus Geiger board, we used 9V battery from Hrannar. That showedgreat results as we only had to replace those once.

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Executive summary

This chapter outlines main work procedure of this project and how we tried to meet the projectscope. More detail about each phase can be found in the project management section.

1. Phase � Gather suppliesFirst we made part list and acquired necessary supplies, see resources section for details.

2. Phase � AssembleFirst we assembled belts and wired DC motors and arduino to motorcontroller. Then wewired two state buttons and indicator LEDs to batteries.

Next after lots of testing we wired Geiger board to LCD. Trying to steal a pin from eitherthe LCD or the LEDs on the board. Since the LCD has 8 data bus pins but can workwith 4 pins[pin11]. Finally when the testing phase was exhausted we made the protectionbox, �nishing scope nr.5

LCD pin name Rs EN DB4 DB5 DB6 DB7Arduino pin 3 4 5 6 7 8

Table 1: Map of Arduino pin we used for LCD

LED array 1 2 3 4 5Arduino pin 9 10 11 12 13

Table 2: Map of Arduino pin used up by LED array of Geiger board

Analogue pins are used for our Geiger tube

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3. Phase � TestingThis phase Consisted of testing Geiger counter, motor controller, DC motors and LCD.We modi�ed the conversion factor to 0.00792 because the value given by the manufactureris only accurate with the radiation element with which it was calibrated for(60Co). Weadjusted it with a more sophisticated Geiger found in RU physics lab and radiation source(137Caesium) .DC motors and LCD worked �ne. But the pin task came to be a more challenging thananticipated. The LCD only used 4 pins from the manufacturer and rest of the pins wereintegrated into the PCB board of the Geiger unit.

4. Phase � ReportThis phase was done by most parts in parallel with this project. Utilizing previous workdone from project proposal and presentation.

5. Phase � presentationThis phase consisted of writing presentation and present it to audience.

6. Phase � SoftwareThis phase consisted of implementation for driving, utilizing open source code (see detailsin code section). The most tricky part was to adjust the pins so the motors could becontrolled in parallel with the LCD. We tried all possible settings but non worked. Weworked with two open source codes from the internet one for the Geiger counter[ope11a]and the other for the Sabertooth[Ope11b].

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Code

The code was written with the following objectives in mind, the tank should be able todrive, measure radiation in the environment and react accordingly. The �rst problemwas to get the tank to drive, for that we took a code we found on a forum[Ope11b] andchanged it to �t our needs. Those changes were mainly chopping down functions to makethem simpler and easier to �nd errors. Changing input for the drive function. The reasonfor that change was that the original code assumed that both the motors would spin atthe same speed. In reality the motors needed di�erent values to spin at the same velocityso the tank could drive straight.The second problem was to measure the radiation for that we used a source code[ope11a]that is published on the Geiger counter web site. The code works but because of thedesign on the Geiger Arduino board we hit a major hurdle as mentioned in the execu-tive section. The functionality of this code remained very much the same but few minorchanges were made. As with motor code we split this code into smaller function for thesame reasons stated earlier. Also we changed the output for the LCD screen so it printsinformation relative to our project.After the changes had bean made and each of the code tested to assure they worked westarted combining those codes to get the function out if it we desired for the project. Theoutcome of that is what we are returning now.

The code was written in a programming language called Arduino. The language is based[?]on another language called Wiring and the development environment is based on yetanother language called Processing.

We chose to work on it for the sole reason that we had worked with it earlier in thisclass. Although working quite well the program isn't without it �aws. Sometime theerror messages can be a little misleading making it hard to �nd compile errors, anotherproblems it that we couldn't �nd easy way to debug the programs. A possible solutionto this could have been to use Eclipse, but the setup for Eclipse to make it work for theArduino was too steep learning curve for all of us.

Psudocode

The logic or the thinking part of the tank is fairly simple described below are the steppesthe tank takes when driving around in some space looking for radiation.

(a) Start driving.

(b) while driving check if radiation is higher than 0.5 sv, if yes go to step c else repeatstep b.

(c) Stop driving.

(d) Output the radiation level on a LCD screen.

(e) Check if radiation is higher than 0.5 sv, if no go to step a else repeat step e.

To learn more about the code see appendix. It has been thoroughly commented in anattempt to make it easier for people that are not used to reading code to understand it.

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Circuit

The �gure below shows the wiring of our project, implemented using Altium circuitrydesign platform

Figure 7: wiring diagram

This schematic is of the Geiger board.

Figure 8: Schematic of Geiger board[Gei11e]

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Mistakes

We ran into number of mistakes trough out the implementation of our project. Manyidiotically simple other not as intuitive. But always a good lesson learnt. The followingis our list of mistakes and the "how to �x" respectively.

(a) Shorting the battery and melting the battery casing

(b) Loosing contact with batteries within the casing

(c) 4 AA batteries connected in series for the DC motor supply voltage

(d) Not enough current drawn from our supply.

(e) Code does not upload to Arduino properly, needs a restart every time the power isturned o� and back on.

(f) Declaring the use of a pin twice in the code resulted in some strange behaviour fromthe tank.

(g) Not enough pins on the Arduino to run the motors and LCD screen on the sametime.

How to �x

(a) Be careful to wire the buttons in series NOT IN PARALLEL

(b) This came down to poor soldering skills, which melt the plastic. Fixed with solderingpractice

(c) 4 AA batteries connected in series show to be insu�cient, we chose to double it to8 AA, giving us 12.5V ("fresh" batteries).

(d) Never let a single AA go below 1.5V with in the whole supply. Buy new Duracellbatteries and dump Hrannar's crap batteries

(e) Use new Arduino

(f) Not declaring the use of the same pin for two di�erent thing �xed this problem.

(g) Buying Arduino Character LCD Shield (see �gure 9) so that the LCD screen requires2 digital pins instead of 4 or a set of Arduino unos that would communicate together.

Figure 9: Pre-made PCB boards[LCD11] to reduce number of pins needed to operate LCDmodule

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Project management

The project decomposition and a task list was used so we could manage the project better.With the task list we could see what tasks were done and what tasks where left and howmuch time they were estimated to take, and from that we saw if the project was behindschedule. From the decomposition we could see in what order we should do the projectevery item on the decomposition had a id that was also on the task list.

Task list

Estimated time for this project was 77 hours Actual time was about 91 hours The tasksthat took more time then estimated were Implementing, testing, and wiring the LCD.They took about 14 hours more then estimated. Although the project went 14 hours overthe estimated time it was still under the max time for this project which was 121.2 hours.

Figure 10: Task list

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Future work

This robot could be a beginning of a development of a more automated device. In theoryit could perhaps respond to more complex situations in the future if someone would beinterested in mounting motion sensors, web-cam to send video link to human interfaceand a remote control interaction.An interesting approach would be to have the tank back to a given starting point and/ormap the radiation source in space.

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Conclusion

We succeeded 4 out of 5 tasks declared in our scope. We did not succeed in driving anddisplaying data at the same time. It could have been resolved if we had known that theLED array on the Geiger board had been hard wired into the PCB. Then we had ordereda an extra shield as seen in �gure9. The Geiger counter kit did not show accurate readingusing the given CMP to Sieverts/hour conversion factor from manufacturer 0.008120.We calibrated the counter by modifying the conversion factor so it showed same resultsas the more sophisticated Geiger counter found in the RU physics lab. The new factor is0.00792.

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Appendix A

Glossary of technical terms

• Geiger counter ⇒ Is a particle detector that measures ionizing radiation, some-times referred to as a Geiger�Müller counter. It detect the emission of nuclearradiation in the form of :alpha particles, beta particles or gamma rays. Note that itcan not distinguish the energy of the source particle.[URL11a]

• Geiger tube ⇒ A hallow glass tube �lled with inert gas (usually helium, neon orargon with halogens added). It gives an impulse of electricity when a particle ofradiations makes the gas conductive. This brief moment of conduction is ampli�edin the tube by a cascade e�ect, resulting in a outputs of current pulses.[URL11a]

• Motor controller ⇒ A circuit board that takes in signal from a processor toregulate the performance of an electric motor. It can also protect against overloadsand faults.[?]

• Arduino uno ⇒ The o�cial website says: "Arduino is an open-source electronicsprototyping platform based on �exible, easy-to-use hardware and software"[ARD11]

• Siverts ⇒ Unit of biologically e�ective radiation dose.[?]

• PCB board⇒ According to techterms.com[PCB11] it is an abbreviation of "printedcircuit board", as the name suggests it can be described as a circuit board wherethe electrical wires are printed on thin plastic board, connecting di�erent elementstogether.

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Bibliography

[ARD11] Arduino de�nition. Website, 11.20.2011. http://www.arduino.cc/.

[Gei11a] Geiger counter. Website, 11.17.2011. http://www.cooking-hacks.com/

index.php/pack-radiation-sensor-board-for-arduino-geiger-tube.

html.

[Gei11b] Geiger board �gure. Website, 11.23.2011. http://www.

cooking-hacks.com/index.php/documentation/tutorials/

geiger-counter-arduino-radiation-sensor-board#intro.

[Gei11c] Geiger tube �gure. Website, 11.23.2011. http://www.



[Gei11d] Geiger tube specs. Website, 11.26.2011. http://www.



[Gei11e] Geiger schematic. Website, 11.27.2011. https://docs.google.com/

viewer?url=http%3A%2F%2Fwww.cooking-hacks.com%2Fskin%2Ffrontend%

2Fdefault%2Fcooking%2Fimages%2Fcatalog%2Fdocumentation%2Fgeiger_

counter_arduino_radiation_sensor_board%2Fradiation_board_v2.pdf.

[iRo11] Irobot 510 packbot. Website, 11.17.2011. http://www.irobot.com/gi/

filelibrary/pdfs/robots/iRobot_510_PackBot_2011.pdf.

[LCD11] Lcdsheild. Website, 11.20.2011. http://emartee.com/product/42005/

Arduino%20Character%20LCD%20Shield%20With%20LCD1602.

[NOr11] No search result. Website, 11.20.2011. https://www.google.com/search?

gcx=c&sourceid=chrome&ie=UTF-8&q=HG37D670WE12-052FH.

[ope11a] Geiger counter code. Website, 11.19.2011. http://www.cooking-hacks.

com/skin/frontend/default/cooking/images/catalog/documentation/

geiger_counter_arduino_radiation_sensor_board/geiger_counter.pde.

[Ope11b] Motor controller code. Website, 11.19.2011. http:

//forums.trossenrobotics.com/showthread.php?

3636-Arduino-and-Sabertooth-2x5.

[Pac11] Packbot 510 �gure. Website, 11.20.2011. http://www.irobot.com/gi/

filelibrary/pdfs/robots/iRobot_510_PackBot_2011.pdf.

[PCB11] Pcb de�nition. Website, 11.27.2011. http://www.techterms.com/

definition/pcb.

[pin11] Lcd 4 pin mode. Website, 11.23.2011. http://www.ladyada.net/learn/lcd/charlcd.html.

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BIBLIOGRAPHY � Reykjavik University - Fall 2011 - T-411-MECH � BIBLIOGRAPHY

[Sab11] Sabertooth 2x5 data sheet. Website, 11.26.2011. https://docs.google.com/viewer?url=http%3A%2F%2Fdimensionengineering.com%2Fdatasheets%

2FSabertooth2x5.doc.

[Tra11] Traxter kit parts. Website, 11.26.2011. https://docs.google.com/viewer?

url=http%3A%2F%2Fwww.roboticsconnection.com%2Fmultimedia%2Fdocs%

2FTraxster_Assembly_Manual_v1.0.pdf.

[URL11a] Geiger counter tube def. Website, 11.17.2011.

[URL11b] Princeton univerity, environmental health and safety. Website, 11.17.2011.

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