Zuraiz Science Library

Remote Control Robotics Some may argue that a robot is not really a robot if it isnt autonomous. Maybe it is or maybe it isn't. Point being, those some are morons. Learning how to implement remote control features into a robot is a very important skill in robot making. To justify it, I will quickly go over robot intelligent control methods . . . Introductory to Robot Intelligence There is actually a spectrum for robot intelligence. Fully remote control and fully autonomous are not your only options. Instead you should decide what level of intelligence you wish your robot to have. Generally assume the more intelligent, the more difficult to build. Here are the main categories: Automaton 'Intelligence' The lowest level of robot 'intelligence' is a simple automaton device. My definition of an automaton is a device where there is absolutely zero decisions made no matter the given environment. They are simple devices where the action it does is repetitive and automatic. A simple circuit with a motor or a combination of gears and a spring could easily be an automaton. Ever hear of those 'robots' from the 1800's that apparently can write names and poems and other useless stuff? They were very well designed gear integrations. However these 'robots' would keep writing even if the ink well ran out of ink . . . The device simply has no fault tolerance, and will continue attempting the action. They did not even have a method to sense the environment - a requirement of decision making. BEAM 'robots' basically fall into the same category, except they are made from very well designed electronics instead of gears. Remote Control 'Intelligence' Remote control is the next level of robot 'intelligence.' Our current technology is capable of building so many machines physically capable of so much more than any lifeform on our planet. Our planes fly many times the speed of sound, our everyday cars can cross the Sahara Desert in days, but our best computers cannot even match a roach brain in terms of autonomy. Solution? Put the human brain in the driving seat of our machines. This allows for the best of both worlds. Strength and expendability of a machine, brain of a human. Battlebots is a perfect example. Teleoperation Teleoperation is one step above remote control. The advantage a computer has over the human brain is speed. A typical home computer today can crunch more numbers in a few seconds than a human can in an entire lifetime. But despite that speed, the computer does not have a good understanding of the situation. Added to that, our most advanced electronic sensors cannot match our human eyes and ears for observing the situation. Solution? Let the human make the decisions, but have the computer carry them out. A perfect use for this would be a robot spider. A human operator in no way can control 8 legs with 3 joints each. Instead, the human would give commands like 'go forward' or 'rotate' and the computer will handle the rest. This method is also very common with space robots because of the long transmission delay. Full Autonomy Fully autonomous robots are still a dream. It is a huge area in current state-of-the-art robotics research. It concerns artificial intelligence, consciousness, advanced sensory percerption . . . the list goes on. Huge philosphical implications as well. But all this is out of the scope of this tutorial. If you make a robot that can intentionally navigate from your couch to your kitchen and back without any collisions all by itself, you have built an autonomous robot. But if it fails to bring a beer back you are still a beginner in my eyes . . . How to Build a Remote Control Robot The remote control robot is probably the easiest of all robots you can make. A complete beginner can probably make a basic remote control robot in under an hour. The electronics part is plug-n-play, the robot chassis being what will take a little time. Remote control robotics is great for those who want to build a robot - yet does not have enough time, skill, and/or patience to so see a large project through to completion. Have a look at an example of a wall climbing robot with an arm. First, a video to help you get started: All you need is a few cheap commercially available items: Remote Control Transmitter The remote control transmitter is the handheld thingy with knobs and buttons and a long intenna sticking out of it. This will be the most expensive part you need to buy, around $40-$200. It will require it's own battery and battery charger. The remote control transmitter usually has very good range. Once as a test, I put my robot in the basement of a building, climbed to floor 10, then operated it without any issues. If you plan to ever do USAR (Urban Search and Rescue), this is a useful feature. The most important feature you need to be concerned with is number of channels it can operate on. Each channel allows you to control one more item on your robot. I recommend at least three, but I have often used up to six on a single robot in the past. Receiver The receiver is a small little box thingy that you put on your robot. It accepts the signal from your transmitter, processes it, then outputs a servo ready signal. This will be the second most expensive part, usually around $30-$60. It will require around ~5V to power it. Receivers can get really small: If you want to use a higher voltage for the servos, get something called a Y-harness (see below image). You simply attach it to a servo port, and then attach your higher voltage batteries and your servo to the other end. Read the instructions for power! Like with the transmitter, you must be concerned with how many channels you would like to have. Operating Frequency Crystal Both your transmitter and your receiver will each require a crystal. These are necessary to ensure both of your devices are operating under the same frequency (so purchase both crystals with the same channel!!!). For RC, there are two frequencies you need to be aware of. One is for air and one is for surface. Remember, its illegal and bad practice to control a remote control car with an air frequency. You could accidently cause someone's remote control aircraft to crash and kill some poor cute innocent squirrel! But you already knew that . . . When you purchase your receiver/transmitter, they will specify whether it should be used for air or surface RC. Another note, the crystal is fragile. If your remote control vehicle crashes a lot, the crystal could get damaged. I once made a robot for a USAR competition that was designed to handle 7 foot drops. But apparently the crystal was not. It broke. Sadness. The solution? Receivers often come with a foam pad thingy to wrap it in for shock absorption. If not, find some foam padding and use it. The crystals usually come as part of your transmitter and receiver, but if not, or if you break one, they cost like $8 plus shipping to replace. The materials above are the basics required for remote control, but you are not yet done. You now need a few more things to build the robot chassis: Optional: Robot Frame Material HDPE and/or aluminum should be used for the frame. Want to build it in 5 minutes? A simple square sheet of HDPE with all parts velcroed on will actually work! But you should attach everything more permanantly for a well designed robot. Optional: Servos Servos, although not required, are designed to be used with remote control vehicles. All you do is literally plug it straight into your receiver and it instantly works. Get two servos - one for each side of your robot - so that you have differential drive. Put a castor in back for balance. You can also use additional servos for other things such rotating a camera, lifting a shovel, or operating a robot arm. If you are on a strict budget, I highly recommend the Hitec HS-311 servos. They only cost about $8 and work really well for what you need. But of course, the $30 servos work even better . . . And here is how to mount servos onto a robot chassis. Optional: Teleoperation Now you do not need a microcontroller for any basic remote controlled robot. But if you want it teleoperational, you must have something to process your commands. So how does this work? The basic concept is - send a command with the transmitter to the receiver - the receiver then outputs a servo square wave - a simple resistor capacitor circuit changes this square wave to an analog value - and then an analog port on your microcontroller interprets this analog value into a particular command, based upon your written program. The servo signal to analog signal converter circuit: Optional: High Power Motor Driver / Speed Controller If you want a high powered robot that uses something much more powerful than hobby servos, you would instead want a motor driver. Most on the market should directly accept a signal made for a servo, and convert that to what you would need for DC motors. Just hook this device up to your receiver, and attach your motors and battery to it, and by happy squirrels you have an instant Battlebot. Be aware that these can get a little expensive, and many are only capable of handling a single motor - meaning you would need to buy two. Optional: Speed Controller The speed controller is basically an H-bridge that operates by a remote control signal. Plug one wire into the receiver, two onto the battery leads, and two on the motor leads - and wallah its controllable by your transmitter. If you wanted to build a fast dc motor driven remote control vehicle, or perhaps need a motor to drive the weapon of your battle bot, this is the way to go. Last Step: Assembly of your Remote Control Robot I figure the best way to explain this is to show an example. This particular robot was made by me and a friend in less than 5 hours back in early 2003. It uses somewhat expensive lexan plates, a lego castor, and super glue, double sided sticky tape, and velcro to connect everything together. Ghetto, yes. But it held together really well and was easy/quick to make. It was designed to play soccer, but since I lived in Pittsburgh at the time there was also plenty of snow to shovel . . . Here is a video of it in action: The remote control that I used was the Laser 6. And here are two teams of remote controlled soccer robots all made in the same fasion: Radio Frequency Reference Chart On rare occasions you may want to know what frequency you are broadcasting on, and not just which channel it is. For example, if your remote control robot is for an underwater environment, you would want the lowest frequency possible to minimize attenuation (interference). 72 megahertz, Channels 11 - 60: This is the most popular choice for flying models. Most radios designed for model aircraft and helicopters will be available on these channels. DO NOT use this frequency for anything other than aircraft, as you could unintentionally cause a crash of someone else's remote control aircraft nearby. Big deal? Not so big when they lose hundreds in $$ from damage, or even worse, a death or injury results from the crash . . . 75 megahertz, Channels 61-90: Cars, boats, and other non-flying models must use one of these channels. Pistol grip radios are available on 27 MHz as well as 75. 27 megahertz, Channels A1-A6 and 50 megahertz, Channels 00-09: While legal for air or surface use, we recommend that 27MHz be used only for surface models. A pilot and driver broadcasting on the same 27MHz frequency would cause interference and could cause a crash. 50MHz channels can be used for R/C, but require the user to attain a Technician-class Amateur Radio License from the FCC. Aircraft Use Only (72 MHz) Channel Frequency 11 72.010 12 72.030 13 72.050 14 72.070 15 72.090 16 72.110 17 72.130 18 72.150 19 72.170 20 72.190 21 72.210 22 72.230 23 72.250 24 72.270 25 72.290 26 72.310 27 72.330 28 72.350 29 72.370 30 72.390 31 72.410 32 72.430 33 72.450 34 72.470 35 72.490 36 72.510 37 72.530 38 72.550 39 72.570 40 72.590 41 72.610 42 72.630 43 72.650 44 72.670 45 72.690 46 72.710 47 72.730 48 72.750 49 72.770 50 72.790 51 72.810 52 72.830 53 72.850 54 72.870 55 72.890 56 72.910 57 72.930 58 72.950 59 72.970 60 72.990 Surface Use Only (75 MHz) Channel Frequency 61 75.410 62 75.430 63 75.450 64 75.470 65 75.490 66 75.510 67 75.530 68 75.450 69 75.570 70 75.590 71 75.610 72 75.630 73 75.650 74 75.670 75 75.690 76 75.710 77 75.730 78 75.750 79 75.770 80 75.790 81 75.810 82 75.830 83 75.850 84 75.870 85 75.890 86 75.910 87 75.930 88 75.950 89 75.970 90 75.990 All Uses (27 & 50 MHz) Channel Frequency A1 26.995 A2 27.045 A3 27.095 A4 27.145 A5 27.195 A6 27.255 00 50.800 01 50.820 02 50.840 03 50.860 04 50.880 05 50.900 06 50.920 07 50.940 08 50.960 09 50.980

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Whether you are an engineering student building a multi terrain vehicle or an electronics hobbyist trying to impress people with your skills, Making a RC robot car (wireless)  is much better than the wired robot which you will have to tail while driving.
Here is a simple, yet informative post for beginners in the field of robotics. Mind you, this not robotics. This is just a toy with which you can play around and still get a hold of the basic concepts in building robots. You can check out some our archives for more tutorials on robotics.
To sum it up, there is one hell lot to do before going around telling people ‘I build robots’ but hey you got to start somewhere right?

Objectives

We will discuss a basic ‘Land Rover’ with nothing. Well not exactly nothing, but nothing complex. As I mentioned earlier this is a really simple project, so simple that not even an embedded computer (microcontroller) is used.
The emphasis is just on the mechanical design and some basic circuitry. We learn the interface of the commercially available RF transmitter and receiver module coupled with HT12E/D pair (Encoder/Decoder) to transfer data over the air to the motor driver L293D.

Things you will need:

These are the things that you will need. Most of them are really common and can be bought in local stores. If you can’t find something, you can always get it form online vendors.
Just be extra cautious when buying the RF Rx-Tx module. They are really fragile and can be rendered unusable before even you had seen them properly.

1. DC Geared motors
2. Wheels
3. Metallic chassis
4. L293D motor driver IC
5. DPDT switch
6. HT12E encoder IC
7. HT12D decoder IC
8. RF Rx-Tx Module
9. 12V Battery pack
10. Some basic tools and soldering iron.

Working Logic for the RC Robot Car

Understanding Datasheets

The next step is to learn how to access the data sheet for the components that you are using. Its actually not that big a deal, just Google the component name and you are provided with numerous links to the datasheet. The real tricky part is to find what you are looking for in the PDF file that you just downloaded.
The data sheet is the only sole documentation that the manufacturer provides for his product so it will contain all the electrical parameters such as the max-min current rating for that device and its V-I characteristics.
Most of the time, such in-depth knowledge about these parameter are not really a must. Although you need to know the VI-ratting and pin description. So finding what you really need form the data sheet comes over practice. You, almost every time will have to look for the,

1. Input Voltage and Current
2. Operating temperature
3. Logic Level
4. Pin description
5. Timing diagram
6. Application Circuit

Hardware

Now that the basic requirements are made, let’s get into the hardware. Mounting the motors on the chassis and the wheels to the motors is something that you should be able to do with little or no difficulty at all. So I will leave it for a self study. Beyond this step you should be more care full.
Now solder some wires on to the motors (if they are not already there) and excite them with power supply and mark which direction they spin for a given polarity. Do the same for the same for all the other motors. Once the marking is done. Short the terminals of the motors on the same side of the bot.
The idea is that the motors on one side of the robot should spin in one direction if excited with a particular polarity. So the motors should be wired something like this,

In this way you have 2 wires from 2 motors instead of 4 wires (2 from each motor). Repeat the same process for another pair of motors and get two more wires. Now you will have 2 + 2 = 4 motors, and 4 wires from entire set.
Once all the four motors are paired and only four terminals are available for excitation you can get started with the actual circuitry. Now go ahead and read about L293D. It is a dual H-bridge motor driver to be short. It is used to drive the motor in both forward and back ward direction.

Direction Control

For the direction control section we are going to be using what is called the Differential Drive algorithm. I know it sound fancy but that’s no big deal. Since we have paired one set of motors to the left of the remote car, we will call this pair the left or right pair based on side of the car they are present.

Left Motor Pair	Right Motor Pair	Direction
Front	Front	Front
Front	Back	Right
Back	Front	Left
Back	Back	Back

As you should have guessed, the car will go front or back if both  the pair of motors operate in one direction and left or right if they operate in different directions.

RF Transmitter Receiver Pair

Now here is what the RF transmitter and receiver modules will look like. There are a verity of manufacturers so don’t panic if your modules are looking different. Even the frequency in which they communicate should not be a problem as long as both the receiver and the transmitter are of the same frequency. All modules are Pin and Pad compatible in case you are planning to design a PCB.

Power Supply

This is the power supply schematic. It has a 7805 to regulate the input 12V to 5V. There is a DC power jack to which the power supply has to be plugged in. The switch is used to turn ON and OFF the power supply.

The receiver Schematic for the RC Robot Car:

This is the circuit diagram for the receiver. It has the RF Receiver module connected to e decoder to decode the data that is being sent from the transmitter. The decoded 4 bit data is then given to the motor diver L293D as input logic to drive the motor.

Preparing the remote control

The remote control will have two DPDT switched like the one shown below. They are to be used for direction control of the remote car. The connection is simple, take a wire and short the opposite extreme pins of the DPDT switch as shown in the right side image. So far you should have used up 4 pins of the switch and 2 more pins left for connections.
In the image below I have labelled them as A, B, C, and D corresponding to the two switches. These 4 pins should be connected to the 4 pins in the transmitter circuit (yet to be discussed) with the same names.

The Transmitter Schematic for RC Robot Car:

Now for the transmitter circuit, you will have to bear in mind that this is your remote (this along with the DPDT switch). So try to make it as handy as possible. Trust me the last thing what is a remote that is too big/heavy to carry around. Make a good closure for this circuit.
Unlike the receiver, this does not need to have a beefy battery. You could power this circuit with a 9V battery. Again here there is a connection box labelled To DPDT switch. Here you have to connect the terminals form the switch following the appropriate names. The last two pins +5v and GND terminals in this circuit is for the power supply to the DPDT switch and can be ignored if you have already given power by some other means.

That’s all for a getting started to robotics (well it is not exactly robotics) There is a lot more to learn beyond this point. This should have cleared some of the basics up for beginners and a total waste of time for the advanced readers  anyway, since its all done lets feel happy about it in either cases.
This is the car that I made. But this is slightly different form the one explained. It uses a TSOP 1738 receiver to receive IR data from a typical TV remote to control the bots movement. Other than fact that it uses Infra red communication instead of a radio frequency they are the same. It is more complicated in terms of code than the one described above (it is a post for another day).
This is the a small video that I made when I made this bot. It shows the parts quiet clearly (or slowly I should say) Please ignore my sense of music if you didn’t like it and if you did leave a comment.

Testing your Circuit

Since this post was published, readers have have run into various kinds of problems while trying to make the remote controlled robot car. This is a very simple circuit and yet you will be surprised if I told your there are more then a dozen place where you could go wrong. I took the trouble of going through all the comments in this post and compiled a list of all the problems that my readers have run into and the solutions that I have given them into a separate post with tips, tricks and techniques that will help you debug the circuit once you have made it.
I strongly suggest you to read the post Circuit Debugging – Tips Trick and Techniques before attempting to make your own rc robot car. If you are still having any doubts, post your comment in that article and I will try my best to help you out.
In the mean time you might want to read about some more advanced robots that we have in our Robotics Archives. For making any robot you should have a reasonably good knowledge on embedded systems and basic electronics and mechanics.