Automated Vacuum Machine

Friday, August 09, 2002

Group Members:Juliya Golubovich

Tasnim PinkyIan McClain-Sewer

AbstractEngineers are always out to improve something, and in the

process make our lives simpler. After learning about the capabilities of a micro controller, a kind of computer without input or output devices, a question was posed: How can a micro controller be put to practical use? To make life easier, an automated vacuum cleaner could be constructed. Constructing this vacuum cleaner provided a lot of experience in the realm of making something as conveniently as possible. Buying a rechargeable dust buster was useful, because new batteries do not have to be purchased, and it does not need to be plugged into the outlet. Also, to be able to use a reasonably low voltage, relays were employed. They allowed a small input into the motors, and a big output. The initial design of the vacuum failed, mainly due to the motors’ lack of power. To solve this problem, the simple motors were replaced with ones already attached to gears.

IntroductionThe objective of this project was to make an Automated Vacuum

Machine using the principles of Mechatronics, the synergistic application of mechanical engineering, electronics, computational hardware and software, and controls. Mechatronics open up a world of automation. In this case, the automated vacuum cleaner would save time. This product would be helpful for the users to get the cleaning done without even actually having to do the vacuuming themselves, which would save them a lot of time and labor. This machine can also be helpful for the handicapped, the elderly, and those who are frail, to have a better life.

Dust-o-Bot is the name of this automated vacuum machine. The micro-controller was programmed via a programming language called PBasic to make two motors (both attached to rubber wheels) turn for the machine to move up and down a room. Before the platform hit a wall, an Infrared Optic Sensor would detect the wall, and the program would get activated, sending a signal to the platform to make a left U-turn. Using a PBasic command called a for-next loop, at the next wall the platform was programmed to turn right, then left again, and so on. As a result of going up and down, the platform would eventually vacuum the entire room. The wheels failed to turn because the apparatus lacked the necessary power. To solve this problem, the motors were replaced with ones attached to gears. The gears allowed for the apparatus to convert the rotational speed of the wheels to additional hauling power, via a difference in gear width within a gearbox of the motor. As a result of the addition of gears, the second design accomplished its task, giving the wheels the power to turn the vacuum's platform.

Background

1. RelayA relay is simply an electromechanical switch made of an

electromagnet and a collection of contacts (a switch and spring). The function of a relay is to use a small amount of power in the electromagnet– coming from a low-power electronic circuit, to move an armature that is able to switch a much larger amount of power. The concept behind an electromagnet is clear-cut: By running electric current through a wire, a magnetic field can be produced. The spring holds the switch in a certain position, until a current is sent through the coil. The coil creates a magnetic field, which shifts the switch. A very

small amount of current can trigger a relay, and the switch can often handle a lot of current. The most familiar relay coil is a length of magnet wire twisted around a metal core. When voltage is applied to the coil, electricity flows through the wire and generates a magnetic field. This magnetic field draws the contacts together and keeps them there until the current stops flowing through the coil. (Figure 3)

Figure 3 Relay Wire twisted around metal core

Figure1 1- Amp SPST Reed Relay- 5 VDC

Figure 2 RelayCapacity: 120 VAC at 50 to 60 Hz

2. MotorsA simple motor is made up of an armature or rotor, commutator,

brushes, axle, field magnet, and DC power supply. An electric motor makes use of magnets to create motion. In two bar magnets with their ends marked "north" and "south," the south end of one will pull at the north end of the other one. Consequently, the south end of one magnet will repel the south end of the other (same goes for the two north ends). These attracting and repelling forces generate rotational motion.

Figure 4 Inside a motor

Figure 5 External of motor

3. Micro-controllerA micro-controller is a computer without input or output devices,

namely keyboards, mice, monitors, and printers. Therefore, its not meant to “talk to people.” Micro-controllers are implanted in other devices, like televisions, so they can control the product. Hence, a micro-controller is also called “embedded controller.” Micro-controllers perform only one job at a time on one specific program. This program is stored in the micro-controller Electronically Erasable Programmable Read-Only Memory (EEPROM). The EEPROM can be changed without changing the chip. In addition, the chip’s data does not need to be completely erased to change its programming. Unlike desktops, micro-controllers are low power, and can run on a battery, taking up about 50 milli watts. A micro-controller often has a small LED or LCD display for output. A micro-controller also takes input from the device it is running and in turn controls it by sending signals to its different components. The average low-end micro-controller chip might have 1,000 bytes of ROM and 20 bytes of RAM on the chip, along with many of I/0 pins. Random access memory has to be refreshed all of the time or it forgets what it is holding. The microprocessor then carries out these instructions without additional human interference.

One type of micro-controller is the "BASIC Stamp", created by a company called Parallax. A BASIC Stamp is adapted to recognize the BASIC programming language. PBASIC makes it very easy to make software for the controller. The micro-controller chip can be bought on a small carrier board that works with a 9-volt battery. Plugging it into a port of a desktop computer after a program has been written for it in PBASIC can program it.

4. Infrared Sensor

An infrared sensor consists of two parts, an infrared transmitter and receiver. The infrared transmitter sends infrared light, usually at a peak wavelength of between 880 and 950 nm, into the volume of space immediately adjacent to the sensor, in this case the front of the Plexiglas. Operation is based upon recognition of infrared light reflected back into the infrared receiver from objects that come within the certain range. That is, from objects that enters the space illuminated by the sensor.

When sufficient infrared light is reflected back into the sensor, a detection signal is generated. The motors respond to the detection signal by making a turn. The sensor sends a signal to one motor to stop, and to the other to continue.

Figure 6 BASIC stamp by PARALLAX

Figure 7 (micro-controller) BASIC stamp II

5. GearsGears are used in many mechanical devices. Their most

important job is providing a gear reduction in equipment containing motors. Often, a small, fast-spinning motor can provide enough power for a device, but not enough torque (torque= force x diameter). With a gear reduction, the output speed can be reduced and torque increased.

On any gear, the distance from the center of the gear to the point of contact determines the ratio. In a device containing two gears, if one gear is twice the size of the other, the ratio would be 2:1, or if one gear were four times the other, the ratio would be 4:1. Spur gears are the most frequently used. (Figure 8) They have straight teeth, and are mounted on parallel shafts. At times, many spur gears are used simultaneously to produce very large gear reductions.

Figure 8 IR sensor and IR receiver

Equipment list(1)Rev A Board of Education(1)Radioshack 9.6 V Turbo Racing Battery Pack (Varies) jumper wires(2)100 microfarad capacitors(2)4.7 kilo Ohm +- 5% resistors(1) 220 Ohm resistor(2) .01 microfarad capacitors(3) 2 Light Emitting Diodes(1) NPN transistor(2) 5V DC Single Pulse Single Throw relays(1)On/off switch(2)3.9 Ohm resistors(1)47 Ohm resistor(1)Breadboard(1)IR transmitter(1)IR detector(1)BASIC Stamp II (Micro-controller)(10) 8 mm bolts

Figure 9 Spur Gears

(10) 8mm nuts(10) 8mm washers(2)36 V DC motors (with interior gear attachments)(1)Hand vacuum(1)Free wheel(1)14 by 11.5 by.25 piece of Plexiglas(1) Rubber pipe(2) 5.25 in (diameter) wheels(1) 9V battery(2) L-shaped aluminum pieces(1) Computer (with pBASIC programming)

Schematic/ program

'{$STAMP BS2}'*********************************************************************************'*********************************************************************************'** **

IR Receiver

IR

Figure 10 Schematic of the Platform Circuitry

Figure 11 IR Receiver and IR Transmitter

'** **'** Vacrobot (Automatic Vacuum Machine) **'** **'** July 31,2002 SANG-HOON LEE **'** **'** POLYTECHNIC UNIVERSITY, BROOKLYN NY **'** **'** SUMMER RESEARCH 2002 **'** **'** **'** 1. INITAL STARTING POSOTION IN ROOM IS RIGHT. **'** 2. IT GOES FRONT IN THE BEGINNING. **'** 3. IT MAKES LEFT TURN WHEN IT MEETS A WALL. **'** 4. IT GOES FRONT AGAIN. **'** 5. IT MAKES RIGHT TURN WHEN IT MEETS ANOTHER WALL. **'** 6. IT DOES JOB 3, 4 AND 5 ALTERNATIVELY. **'** **'** **'*********************************************************************************'*********************************************************************************

'--------------------------------------------------'DECLARATION

IR var biti var wordj var wordk var word

i = 0j = 0

output 7

main:

'--------------------------------------------------' SENDING AND RECEIVING IR TO DETECH A WALL

freqout 7, 1, 38500IR = in2

debug home, "IR= ",bin1 IR," i= ",bin1 i, " j= ", bin1 j, " k= ", bin1 kpause 20

if IR = 0 then turn ' MEET WALL

forward:

high 0high 11

goto main

turn:i = i+1 'TO MAKE LEFT AND RIGHT TURN ALTERNATIVELYj = (i/2)*2

if i = j then right_turn

left_turn:for k =1 to 5000low 0high 11next

goto main

right_turn:

for k =1 to 5000high 0low 11next

goto main

Wheel

Micro-controller

InfraredTransmitter

9.6 V battery

Motor(withGearattachments)

RelayInfraredReceiver

AnalysisAfter the 1st prototype was put together, testing showed that the

wheels needed to be calibrated because the motors had slightly different rotational speeds when supplied with the same voltage. To do so, a network of resistors and a potentiometer were connected to the slower motor. The potentiometer, which could be turned clockwise or counterclockwise, either sped the motor up or slowed it down. After finding the potentiometer setting that made both motors turn at the same speed, another problem arose: the mobile platform was unable to turn because of a lack of power. Another problem with the first prototype was that in making its left turn; the back of the Plexiglas would hit the wall and get stuck. The second model dealt with all of these problems.

The turning problem found in the first model was solved when the simple motors were replaced with two more powerful ones with built in gear mechanisms. Theoretically, there were 4 or 5 gears inside, with the motor attached to the smallest one. The smaller gear turned the larger gear, which turned a larger gear and so on. The gears solved our problem because it gave the mobile platform the extra torque, the ability to make an object rotate, by increasing the diameter of the mechanism turning the wheels. The problem regarding the Plexiglas’s square shape and its related turning difficulties was resolved in the second model by curving the back corners were curved, giving the vacuum’s body a circular shape. When the vacuum cleaner hit the wall during is left turn, the curved edges gave the platform the ability to

Figure 12 Dust-o-Bot Vacuum Machine (topside view)

make smoother contact, lessening the chances of a major path alteration. The second model, however, also had flaws.

In the second model of the automated vacuum, the potentiometer was not incorporated. Instead, to fine-tune the movement of the motors, the program was altered. The amount of seconds the vacuum had to make its right and left turns were changed. Both turns initially had 5 seconds to them. The time for the left turn was then increased, and the time for right turn decreased. Ultimately the results were as follows:

left turn:for k=1 to 5060low 0high 11next

right turn:for k=1 to 4980high 0low 11next

Another major problem in the design of the second model that has yet to be resolved was the ineffectiveness of the infrared sensor. Depending on the color of the obstacle, the IR sensor would detect its presence at differing distances, due to the varying degrees of reflected infrared light. For example, the IR sensor detected a black surface at the appropriate time, allowing the platform and the vacuum cleaner to vacuum the area closest to the obstacle before turning. However, the infrared sensor detected a white obstacle far too early. The platform,

therefore, came nowhere near the obstacle before turning. When placed in front of a gray obstacle, the IR sensor failed to detect its presence completely.

ConclusionThe engineering goal set at the onset of the experiment was to

create a working autonomous vacuum cleaner. In order for this to have happened the wheels needed to be calibrated properly and gears needed to be added. Luckily, this was accomplished in one step, that is, the second set of motors already had built-in gears. This project, which is still at the prototype stage, can be improved in many ways. Presently, in order for the apparatus to function properly, the room needs to have black borders within the infrared sensors’ detection range. In the future, either new sensors need to be implemented in place of the infrared sensor, or the IR sensor can be improved via programming. Additional object detection, to deal with more complicated obstacle placement, can also be researched. The device itself could also be made compact. Aesthetic elements can also be added, such as an attractive covering to protect the inner workings of the apparatus. The vacuum should be reprogrammed to take into consideration a room filled with furniture. A back move may be added to the program in case the vacuum bumps into something.

References

Brain, Marshall. “How Relays Work.” Howstuffworks, Inc. 1998-2002. http:// www.howstuffworks.com/relay.htm (6 Aug. 2002)

Brain, Marshall. “How Electromagnets Work.” Howstuffworks, Inc. 1998-2002. http://www.howstuffworks.com/electromagnet.htm (6 Aug. 2002)

Krause, Andrew. “Relay Basics” by Andrew Krause http://www.howstuffworks.com/framed.htm?parent=relay.htm&url=http://www.teamrocs.com/technical/pages/relay_basics.htm (6 Aug.2002)

Brain, Marshall. “How Electric Motors Work.” Howstuffworks, Inc. 1998-2002. http://www.howstuffworks.com/motor.htm (6 Aug. 2002)

Brain, Marshall. “How Micro-controllers Work.” Howstuffworks, Inc. 1998-2002. http://www.howstuffworks.com/micro-controller.htm (6 Aug. 2002)

“Infrared (IR) Presence Sensors on Swinging Doors:Genesis of the Problem.” Davis Associates, Inc. 2002. http://www.davis-inc.com/doors/problem.html (6 Aug. 2002)

“Basic Car Audio Electronics: Relay Basics.” http://www.eatel.net/~amptech/elecdisc/caraudio.htm (8 Aug. 2002)

“Compact 1-Amp SPST Reed Relay-5VDC.” Radioshack.com http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F010%5F008%5F001%5F000&product%5Fid=275%2D232 (8 Aug. 2002)

Cowden, David. “Descriptions of the Basic Gear Types.” http://www.howstuffworks.com/framed.htm?parent=gear-ratio.htm&url=http://srl.marc.gatech.edu/education/ME3110/primer/geartit.htm (8 Aug. 2002)

Brain, Marshall. “How Micro-controllers Work.” Howstuffworks, Inc. 1998-2002. http://www.howstuffworks.com/micro-controller2.htm (8 Aug. 2002)

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