Solar car working pdf

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The time now is PM. Copyright FaaDoOEngineers. Imagine if we could capture that energy directly and convert it to a form that could power our cities, homes, and cars! Many scientists around the world are researching how we can improve our use of the sun's energy. One way is to use solar thermal panels to collect thermal energy to heat air and water. Another way is to use photovoltaic PV cells, also called solar cells, to convert sunlight directly into electricity.

PV cells use a material such as silicon to absorb energy from sunlight. The sunlight energy causes some electrons to break free from the silicon atoms in the cell.

Because of how the solar cell is made, these free electrons move to one side of the cell, creating a negative charge and leaving a positive charge on the other side. When the cell is hooked up in a circuit with wires, the electrons will flow through the wires from the negative side to the positive side, just like a battery. This electron flow is electricity, and it will power a load light bulb, car motor , etc. PV cells today are still only able to capture a small fraction of the sun's energy, so acres of them are necessary to collect enough light to create electricity on a large scale.

A lot more scientific work needs to be done to make them more efficient and take up less space. Despite the challenges, solar panels are used to power many things such as emergency signs, school crossing lights, and more. Many people are also able to power their homes by mounting solar panels on the roof, and this will only get easier as the technology continues to advance.

Our products are durable, reliable, and affordable to take you from the field to the lab to the kitchen. They won't let you down, no matter what they're up against. Whether it's over eager young scientists year after year, or rigorous requirements that come once-in-a lifetime.

And if your science inquiry doesn't go as expected, you can expect our customer service team to help. Count on friendly voices at the other end of the phone and expert advice in your inbox. They're not happy until you are. Bottom line? We guarantee our products and service won't mess up your science study—no matter how messy it gets. Home Solar Car Project. Make Your Own Solar Car In this project, you will need creativity and experimentation to design and build a car powered by two solar cells and a small electric motor.

Adult supervision is recommended for this project. What You Need for a Solar Car Project 2 solar cells alligator clip leads Rubber bands Small electric motor Look at hobby or electronics stores, and make sure you get one with a motor pulley For the car body: cardboard milk carton, water bottle, cardboard, foam board, or similar materials For the front wheels and back wheels: plastic bottle caps, film canister caps, toy wheels such as K'nex, etc.

Think carefully about this: you want something strong, but also something lightweight so it needs less power for the motor to move it. But be careful — if it's too light, it can easily get blown about by the wind. A big part of engineering is finding the right balance between weight and strength. Use a nail to poke a small hole in the center of your wheels. Make sure the stiff wire or wooden skewers you use for axles fit in the holes tightly.

Dc motors use a variety of permanent-magnet materials. Early designs employed ceramic or ferrite and AlNiCo magnets. These materials are still widely applied, however, in automobiles and other areas where low cost as well as reliability is important.

Newer designs use rare-earth samarium-cobalt and neodymium magnets. Most magnets have stable magnetic properties within the normal operating temperature range of the motor. But some magnets have a higher temperature coefficient than others. High temperature-coefficient magnets may become too weak if operated at high temperatures for extended periods. Depending on the magnetic material and slope of the motor's magnetic circuit, torque degradation may result over a wide temperature range.

Ceramic or ferrite magnets lose about 0. But this loss is generally reversible if the temperature is kept within the motor rating. Colder temperatures are seldom a problem. Since the coefficient curve is linear, magnets are stronger at lower temperatures. Some grades of rare-earth magnets are more sensitive to temperature than others. Magnets in the neodymium family may have irreversible magnetic losses under wide temperature changes.

These magnets have the highest maximum-energy product MEP , a figure of merit, of any commercial magnet now available. High MEP comes at a premium and should not be lost to temperature extremes. Neodymium magnets are continually being improved with lower temperature coefficients to make them as stable as other rare-earth grades. Peak loads applied to AlNiCo and ceramic dc motors can degrade their magnetic properties. Current exceeding this rating, caused by either a current spike or a constant dc input, are over the knee and cause permanent demagnetization.

Fortunately, rare-earth magnets are not as sensitive to demagnetization as AlNiCo and ceramic. Advanced DC Motors. Brushless versus brush-type:. Designers planning to integrate a dc motor into a system usually work from a development specification. Constraints and limits in the specifications will largely determine whether a brush-type or a brushless motor is acceptable, based on the qualities of each. Brush-type motors are generally used below 5, rpm. The actual operating speed depends upon the commutator diameter and brush material.

Brush life decreases with higher commutator surface speed. Surface speed for silver-graphite brushes is usually below fpm while paliney brushes are limited to only 50 fpm. Other factors which limit brush motor life include commutator bar-to-bar voltage, brush current density, and power at the brush-commutator interface.

High current and power at the brushes and commutator bar-to-bar voltage not terminal voltage greatly exceeding 15 Vdc produce excessive arcing. Arcing erodes brushes and commutators; wear accelerates once erosion begins. On the other hand, electronic drives for brush motors are usually much simpler than for comparably sized brushless motors. No position sensors or electronics are required for commutation. But these components are mandatory for brushless operation.

Unless used in a servocontrol loop, brush-type dc motors need no electronics other than a power source. Since brushless dc motors have no commutators or brushes, brush and commutator arcing does not limit speed. Brushless dc motors are better suited for applications needing a wide speed range. Speeds from a stalled condition to more than 60, rpm are not unusual.

Brushless motors replace mechanical commutators with electronic switching. Brushless dc motor controllers require a position feedback signal from a sensor inside the motor. The sensor ensures that excitation to the electromagnetic armature field always leads the permanent-magnet field to produce torque. Power transistors drive the armature windings at a specified motor current and voltage level. Most brushless dc motors are constructed with an outer-wound stationary armature and a rotor consisting of permanent magnets.

Rotors of this type are small and have low inertias. And heat transfers more efficiently from the wound armature to ambient air in this configuration because heat dissipates from the armature core to the outer metallic housing, not conducted through the shaft like most brush-type configurations. Motor sizing:. Motor sizing takes into account all the above motor parameters and specifications. Also, the motor inertia and load must be defined for both transient and steady-state conditions.

These inertia are critical since torque during acceleration exceeds torque at constant speed. Two examples explain the sizing of dc motors for typical applications.

The first example considers the selection and sizing of a brush-type dc motor. The second concerns a sterile outer-space environment requiring a brushless dc motor.

The purpose of a motor speed controller is to take a signal representing the demanded speed, and to drive a motor at that speed.

The controller may or may not actually measure the speed of the motor. Feedback speed control is better, but more complicated, and may not be required for a simple robot design. Motors come in a variety of forms, and the speed controller's motor drive output will be different dependent on these forms. The speed controller presented here is designed to drive a simple cheap starter motor from a car, which can be purchased from any scrap yard.

These motors are generally series wound, which means to reverse them, they must be altered slightly. Curtis PMW controller. The speed of a DC motor is directly proportional to the supply voltage, so if we reduce the supply voltage from 12 Volts to 6 Volts, the motor will run at half the speed. How can this be achieved when the battery is fixed at 12 Volts? The speed controller works by varying the average voltage sent to the motor.

It could do this by simply adjusting the voltage sent to the motor, but this is quite inefficient to do. A better way is to switch the motor's supply on and off very quickly. If the switching is fast enough, the motor doesn't notice it, it only notices the average effect. When you watch a film in the cinema, or the television, what you are actually seeing is a series of fixed pictures, which change rapidly enough that your eyes just see the average effect - movement.

Your brain fills in the gaps to give an average effect. Now imagine a light bulb with a switch. When you close the switch, the bulb goes on and is at full brightness, say Watts. When you open the switch it goes off 0 Watts. Now if you close the switch for a fraction of a second, then open it for the same amount of time, the filament won't have time to cool down and heat up, and you will just get an average glow of 50 Watts.

This is how lamp dimmers work, and the same principle is used by speed controllers to drive a motor. When the switch is closed, the motor sees 12 Volts, and when it is open it sees 0 Volts.

If the switch is open for the same amount of time as it is closed, the motor will see an average of 6 Volts, and will run more slowly accordingly. As the amount of time that the voltage is on increases compared with the amount of time that it is off , the average speed of the motor increases. The time that it takes a motor to speed up and slow down under switching conditions is dependant on the inertia of the rotor basically how heavy it is , and how much friction and load torque there is.

The graph below shows the speed of a motor that is being turned on and off fairly slowly:. You can see that the average speed is around , although it varies quite a bit. This is the principle of switch mode speed control. Miniature speed controller and brushless DC motor for radio controlled flight. The frequency of the resulting PWM signal is dependant on the frequency of the ramp waveform.

What frequency do we want? This is not a simple question. Some pros and cons are:. Frequencies between 20Hz and 18kHz may produce audible screaming from the speed controller and motors - this may be an added attraction for your robot! RF interference emitted by the circuit will be worse the higher the switching frequency is.

Therefore the greater the time spent switching compared with the static on and off times, the greater will be the resulting 'switching loss' in the MOSFETs. The higher the switching frequency, the more stable is the current waveform in the motors.

This waveform will be a spiky switching waveform at low frequencies, but at high frequencies the inductance of the motor will smooth this out to an average DC current level proportional to the PWM demand. Tire selection will affect rolling resistance which in turn affects how far the solar car will travel on a given amount of energy. Tires with thicker rubber and wider tread will normally have a higher rolling resistance, which is something to be avoided, and boy racers take note.

Thinner tires running at higher pressure will have less rolling resistance, but are more susceptible to punctures and give a harsher ride. One of the best tires are the Bridgestone Ecopia tires made for solar cars. Unfortunately, they need to be mounted on specially made wheels and require custom made hubs. On the positive side, these tires and wheels are very light.

Some college teams have experimented with bicycle tires but report limited success. Bicycle tires, rims and spokes are not designed for the lateral forces placed on them by non-tilting vehicles weighing several hundred pounds. Motorcycle tires tend to be too heavy and have more rolling resistance, although there may be high pressure tires with low resistance that I don't know about.

If you know of any or are a manufacturer making such, please let me know. Bearing resistance can be reduced by lubricating with light oil. Bearing seals can be cut away at the contact lip to leave most of the seal protection while removing a lot, if not all seal drag. Magnetic seals have been used successfully on other electric vehicles, but may prove too complex for your budget. It is a good idea to get the rolling chassis operational months before your schedule gets critical.

Give the chassis a long a run as possible to prove your bearings, axles, steering and suspension can survive, and to highlight any weaknesses in need of attention. Chassis - and seating 2.

Mechanics - suspension, steering, brakes 3. Motor and drive train 4. Motor controller 5.