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.
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.
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.