Many people consider a robot to be a machine that can operate autonomously. However, if you broaden the definition of "robot" slightly, remote controlled objects can also fall into this category. You may think it's hard to build a remote-controlled robot, it's actually simple if you know how to proceed. This article explains how to do it.
Steps
Step 1. Be aware of what you are going to build
The first step in designing a remote-controlled robot is to recognize that you're not going to build a life-sized, two-legged humanoid robot that can do all your chores. Nor will you build a multi-limb robot that can reach and pick up 100-pound weights. You need to start building a robot that can go forward, backward, left and right, controlled by you wirelessly. However, once you've laid the groundwork and built this simple robot, you'll be able to add and edit several details. Usually you should follow the principle that no robot is ever finished. It can always be improved.
Step 2. Design your robot
Before building it, even before ordering the pieces, you will need to design it. For your first robot you should choose a simple design, with only two servo motors on a piece of plastic. This project is really simple and usually leaves extra room to add extra functionality after making. Think about building something about 15 x 20 cm. You will be able to draw it on paper with a full size ruler precisely because it is quite small. But when you think of a bigger and more complex robot, you should learn how to use CAD or a similar program, such as Google Sketchup.
Step 3. Choose the pieces
It's not time to order the pieces yet, but you should pick them now and know where to buy them. Try to order them from a small number of sites to save on shipping. You will need the frame material, two "servo" motors, a battery, a transmitter and a receiver.
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Choose a servo motor. To move the robot you will need to use motors. The first will give power to one wheel and the second to the other. This way you can implement the simplest method of steering: the differential transmission. This means that the robot will go forward when both motors are spinning forward, will go reverse when both motors are spinning backwards and will run when one motor is active and the other remains stationary. A servo motor differs from a basic DC motor in that it is oriented, it can only turn 180 ° and it can roll back to its position. This project will use servo motors because they make movement easier and you won't have to purchase an expensive "regulator" or separate box of gears. Once you understand how to build a RC robot, you can make another one (or modify the first one) using DC motors, rather than servo motors. There are four basic characteristics you need to worry about when purchasing servo motors: speed, torque, size / weight, and whether they are 360 ° editable. Since the servomotors can only turn 180 °, the robot would only be able to move forward a little. If the motor is 360 ° editable, you can make it spin continuously. Make sure the engine is truly 360 ° editable. Size and weight are not very important in this project, because you will probably have plenty of space. Try to make something medium in size. Torque is the strength of the motors. That's what gears are used for. If there are no gears and the torque is low, the robot will probably not be able to move forward, because it will not have the strength. Try to have a high torque, but the higher it is, the slower the speed generally will be. For this robot, try to get a good balance between speed and torque. You will always be able to purchase and mount a more powerful or faster servomotor after completing the build. Get the HiTec HS-311 servo motor for your first RC (remote controlled, i.e. remote controlled) robot - it has a great balance of speed and torque, is inexpensive and has a size that fits this robot. The HiTec HS-311 servo motor can be bought here.
Since the servo motor can normally only turn 180 degrees, you have to modify it to have continuous rotation. Changing it will void the warranty, but you have to do it. For detailed instructions on how to modify a servomotor go here
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Choose a battery.
You need to get something to power your robot. Don't try to use AC power - you don't have to plug it into the wall. You have to use DC power, i.e. batteries.
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Choose the type of battery. There are three types to choose from: alkaline, NiMH and NiCad, lithium polymer (LiPo).
- Lipo batteries are the latest and extremely light. However, they are dangerous, expensive and require a special charger. Use this type of battery only if you already have robotics experience and are willing to spend more on the robot.
- Nickel-cadmium batteries are common rechargeable batteries. They are embedded in many robots. The biggest problem with these batteries is that if you charge them when they are not fully discharged, they will no longer hold a full charge.
- NiMH batteries are very similar to NiCad batteries in size, weight and price, but generally perform better. These are generally the recommended batteries for a beginner's project.
- Alkaline are common non-rechargeable batteries. You will already have some because they are cheap and easy to find. However they download fast and you have to buy them over and over again. Don't use them.
- Choose the battery specifications. You need to choose a voltage for your battery pack. The most common in robots are 4.8V and 6.0V. With these, most servo motors will move well. It is usually advisable to take the 6.0V (which is fine for most servomotors) as it will allow your servomotor to run faster and have more power. Now you need to address your robot's battery pack capacity, which is in mAh (milliampere / hour). The higher the capacity, the better, but it also gets more expensive and usually heavier. For the size of the robot you are building, around 1800mAh is recommended. If you have to choose between 1450 or 2000 mAh with the same voltage and weight, choose 2000 mAh. It will also be a couple of euros more expensive, but it is still the best multipurpose battery you can get. Make sure you have a charger with which to recharge the battery pack. Here you can buy a 6, 0V and 2000mAh NiMH battery.
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- Choose the material for your robot. You will need a frame to connect all the electronic components. Most robots of this size are made of plastic or aluminum. For a beginner, it is recommended to use a type of plastic called HDPE. This plastic can be processed easily and is cheap. When deciding on the thickness, take it about 5 mm. As for the size of the paper, you will probably have to get a large enough one in case you make a mistake in cutting. It is usually recommended to take at least double the area needed for your robot. A 5 x 600 x 600mm piece of HDPE can be bought here.
- Choose a transmitter / receiver. This will be the most expensive part of your robot. It can also be considered the most important, because without it the robot cannot do anything. It is highly recommended that you purchase a good transmitter / receiver to start with, as it is the device that will limit the robot's features. A cheap transmitter / receiver will move the robot well, but you won't be able to add anything else. In addition, the transmitter can be used for other robots that you will build in the future. So instead of buying a cheap one now and a more expensive one later, buy a better one now. It will save you money in the long run. However, there are several frequencies that you can use. The most common are 27 MHz, 72 and 75 MHz and 2, 4 GHz. The 27 MHz can be used for aircraft or cars. It is commonly used in cheap remote controlled games: it is not recommended except for small projects. 72 MHz can only be used for aircraft. As it is normally used in large models, it is illegal for use in surface vehicles. If you use this frequency, not only are you breaking the law, but it could interfere with an expensive airliner flying nearby. You risk causing a plane crash, with huge repair costs or, worse still, endangering people's lives. The 75 MHz one, on the other hand, is only made for surface use: you could use it. However the frequency of 2.4 GHz is the best. It has less interference than any other frequency. It is advisable to spend a few dollars more to have a 2.4 GHz transmitter with receiver. Once you have decided which frequency to use, you need to determine how many "channels" you will use on the transmitter / receiver. The number of channels practically corresponds to how many functions you can control on your robot. For this robot you need at least two. One channel will allow your robot to go forward / backward and another will allow it to go left or right. However, it is recommended that you have at least three. This is because, after you build the robot, you can always add another function. If you take four, you will usually have two joysticks. With four transmitter / receiver channels you can add a claw at the end. As mentioned before, you should buy the best transmitter / receiver your budget allows now, so you don't have to buy a better one later. You will be able to use the transmitter and receiver again on other robots that you can build in the future. The Spektrum DX5e 5-channel 2.4 GHz Radio System Mode 2 and the AR500 can be purchased together here.
- Choose your wheels. When choosing wheels, the three most important things you need to worry about are diameter, traction, and whether they will easily attach to your motors. The diameter is the length of the wheel from one side to the other, through the central point. The larger the wheel diameter, the faster it goes and the more it can rise, but it will have less torque. If you have a smaller wheel, you may not be able to climb easily or go very fast, but you will have more power. The quality of traction depends on the grip of the wheels on the surface. Make sure you have wheels with a rubber or foam ring so they don't slip. Most servomotor-friendly wheels will be able to be screwed on properly, so you don't have to worry. A type of wheel between 3 and 5 inches in diameter with a rubber ring around it is recommended. You will need two wheels. Precision disc wheels can be purchased here.
Step 4. Now that you have selected the parts, you can proceed with the online order
Try to buy them from a small number of sites to try to save on shipping, especially if you buy everything at the same time.
Step 5. Measure and cut the frame
Take a ruler and a marker and measure the length and width of the frame on the material you intend to use for the frame. It should be done about 15 x 20 cm. Take the right measurements - the lines don't have to be crooked and make sure the length is right. Remember: measurements are taken twice, but can only be cut once! Here: now you can cut. If you use HDPE, you should be able to cut it the same way you cut a piece of wood of the same size.
Step 6. Assemble the robot
Now that you have all your materials and that you have cut the frame, all you have to do is assemble them all together. In reality this can be the easiest step if you have designed the robot well.
- Fit the servomotors to the bottom of the plastic piece, towards the front. They should be placed sideways so that each “horn” of the shaft (the part of the servomotor that moves) faces a side face. Make sure there is enough space to mount the wheels.
- Secure the wheels to the servo, using the screws provided with it.
- Attach one piece of Velcro to the receiver and the other to the battery pack.
- Put two pieces of Velcro on the robot - so that this presents the other side - and attach the receiver and the battery pack to it.
- You should now have a robot showing two wheels in the front and touching the floor in the back instead. There will not be a third wheel on this robot: it is specifically designed for the back to slide along the floor.
Step 7. Connect the wires
Now that the robot is assembled, just plug everything into the receiver. Insert the battery into the receiver socket marked "Battery". Make sure you connect it correctly. Now, connect the servos in the first two channels on the receiver, where you see written "Channel 1" and "Channel 2".
Step 8. Charge the battery
Disconnect the battery from the receiver and connect it to the charger. Wait until the battery is charged. This could take up to 24 hours, so you will need to be patient.
Step 9. Play with your robot
At this point, everything should be fine. To advance it, press forward on the transmitter. Build an obstacle course and use it to play with your cat. Now that everything is ready, have fun with the robot and add more features!
Advice
- You'd better use a 12V DC motorcycle battery, so you can get high speed and torque.
- If you press right and the robot goes left, try swapping the servo input on the receiver: if you connected the right to Channel 1 and the left to Channel 2, swap them.
- Try putting your old smartphone on top of the robot and use it as a video transmitter if it has a camera. You can use it in combination with Google Hangouts as a video chat between the robot and your computer or other device to guide your robot even from outside the room it is in!
- You may need to purchase an adapter that allows you to insert the battery into the charger.
- Add other features. If you have an additional channel on your transmitter / receiver, you can add another servo motor to improve the robot. If you have only one additional channel, try making a clamp that can be closed. If you have two additional channels instead, try making a claw that can open and close, move left and right. Use your imagination.
- Before purchasing, please make sure the transmitter and receiver are on the same frequency. Also, check that the receiver has an equal or greater number of broadcast channels. If there are no more channels in the receiver than in the transmitter, only the minimum amount of channels will be usable.
Warnings
- Using a 12V DC battery you can blow up the engine if it is not 12V DC.
- Do not use the 72 MHz frequency, unless you are building an aircraft. If you use it on a surface vehicle, not only is it illegal, but you could injure or even kill someone.
- Beginners should try not to use AC power (the electrical outlet connection) for any home-made projects. AC power is extremely dangerous.
- Using a 12 V DC battery on a 110 - 240 V AC motor, it will burn and break quickly.
